Initial Commit

.dockerignore

@@ -0,0 +1,7 @@
+node_modules
+.next
+.git
+*.md
+term-2-unit.pdf
+.env*
+.claude

Dockerfile

@@ -0,0 +1,30 @@
+FROM node:20-alpine AS deps
+WORKDIR /app
+COPY package.json package-lock.json ./
+RUN npm ci --ignore-scripts
+
+FROM node:20-alpine AS builder
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY . .
+ENV NEXT_TELEMETRY_DISABLED=1
+RUN npm run build
+
+FROM node:20-alpine AS runner
+WORKDIR /app
+ENV NODE_ENV=production
+ENV NEXT_TELEMETRY_DISABLED=1
+
+RUN addgroup --system --gid 1001 nodejs
+RUN adduser --system --uid 1001 nextjs
+
+COPY --from=builder /app/public ./public
+COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
+COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
+
+USER nextjs
+EXPOSE 3000
+ENV PORT=3000
+ENV HOSTNAME="0.0.0.0"
+
+CMD ["node", "server.js"]

Jenkinsfile

@@ -0,0 +1,58 @@
+pipeline {
+  agent any
+
+  environment {
+    REGISTRY       = 'registry.dwarrington.com'
+    IMAGE_NAME     = 'cabrits'
+    IMAGE_TAG      = "${env.BUILD_NUMBER}"
+    CREDENTIALS_ID = 'registry-creds'
+    SUBDIR         = ''
+    COMPOSE_FILE   = 'docker-compose.yml'
+    SERVICE_NAME   = 'cabrits'
+  }
+
+  stages {
+    stage('Checkout') {
+      steps {
+        checkout scm
+      }
+    }
+
+    stage('Build & Push') {
+      steps {
+        script {
+          docker.withRegistry("https://${REGISTRY}", CREDENTIALS_ID) {
+            def buildArgs = (!env.SUBDIR || env.SUBDIR.trim() == '')
+              ? "-f Dockerfile ."
+              : "-f ${env.SUBDIR}/Dockerfile ${env.SUBDIR}"
+
+            def img = docker.build("${REGISTRY}/${IMAGE_NAME}:${IMAGE_TAG}", buildArgs)
+            img.push()
+            img.push('latest')
+          }
+        }
+      }
+    }
+
+    stage('Deploy') {
+      steps {
+        withCredentials([usernamePassword(
+          credentialsId: CREDENTIALS_ID,
+          usernameVariable: 'DOCKER_USER',
+          passwordVariable: 'DOCKER_PASS'
+        )]) {
+          sh '''
+            export PATH=$PATH:/usr/libexec/docker/cli-plugins:/usr/bin:/usr/local/bin
+
+            echo "$DOCKER_PASS" | docker login ${REGISTRY} -u "$DOCKER_USER" --password-stdin
+
+            sed -i "/${SERVICE_NAME}:/,/image:/s|image:.*|image: ${REGISTRY}/${IMAGE_NAME}:${IMAGE_TAG}|" ${COMPOSE_FILE}
+
+            docker compose -f ${COMPOSE_FILE} pull ${SERVICE_NAME}
+            docker compose -f ${COMPOSE_FILE} up -d --force-recreate --remove-orphans
+          '''
+        }
+      }
+    }
+  }
+}

app/globals.css

@@ -1,26 +1,183 @@
 @import "tailwindcss";
+@import "katex/dist/katex.min.css";
 
 :root {
-  --background: #ffffff;
+  --background: #f4f8ff;
-  --foreground: #171717;
+  --foreground: #10223f;
+  --muted: #4f6588;
+  --border: #cbdaef;
+  --surface: #FFFFFF;
+  --surface-raised: #FFFFFF;
+
+  --unit-1: #2563eb;
+  --unit-1-light: #e8f1ff;
+  --unit-1-dark: #1d4ed8;
+
+  --unit-2: #0ea5a4;
+  --unit-2-light: #e6fffb;
+  --unit-2-dark: #0f766e;
+
+  --unit-3: #f97316;
+  --unit-3-light: #fff1e7;
+  --unit-3-dark: #c2410c;
+
+  --unit-4: #e11d48;
+  --unit-4-light: #ffe8ef;
+  --unit-4-dark: #be123c;
+
+  --correct: #16a34a;
+  --correct-light: #dcfce7;
+  --incorrect: #dc2626;
+  --incorrect-light: #fee2e2;
+  --hint: #d97706;
+  --hint-light: #ffedd5;
+
+  --shadow-sm: 0 1px 2px rgb(16 34 63 / 0.06), 0 2px 8px rgb(37 99 235 / 0.04);
+  --shadow-md: 0 8px 18px rgb(16 34 63 / 0.09), 0 2px 8px rgb(37 99 235 / 0.08);
+  --shadow-lg: 0 16px 30px rgb(16 34 63 / 0.11), 0 6px 20px rgb(37 99 235 / 0.1);
+  --shadow-xl: 0 24px 44px rgb(16 34 63 / 0.14), 0 12px 28px rgb(37 99 235 / 0.12);
+  --shadow-glow: 0 0 24px rgb(37 99 235 / 0.18);
 }
 
 @theme inline {
   --color-background: var(--background);
   --color-foreground: var(--foreground);
-  --font-sans: var(--font-geist-sans);
+  --color-muted: var(--muted);
-  --font-mono: var(--font-geist-mono);
+  --color-border: var(--border);
+  --color-surface: var(--surface);
+  --color-surface-raised: var(--surface-raised);
+
+  --color-unit-1: var(--unit-1);
+  --color-unit-1-light: var(--unit-1-light);
+  --color-unit-1-dark: var(--unit-1-dark);
+  --color-unit-2: var(--unit-2);
+  --color-unit-2-light: var(--unit-2-light);
+  --color-unit-2-dark: var(--unit-2-dark);
+  --color-unit-3: var(--unit-3);
+  --color-unit-3-light: var(--unit-3-light);
+  --color-unit-3-dark: var(--unit-3-dark);
+  --color-unit-4: var(--unit-4);
+  --color-unit-4-light: var(--unit-4-light);
+  --color-unit-4-dark: var(--unit-4-dark);
+
+  --color-correct: var(--correct);
+  --color-correct-light: var(--correct-light);
+  --color-incorrect: var(--incorrect);
+  --color-incorrect-light: var(--incorrect-light);
+  --color-hint: var(--hint);
+  --color-hint-light: var(--hint-light);
+
+  --font-sans: "Nunito", "Trebuchet MS", "Segoe UI", sans-serif;
+  --font-display: "Avenir Next", "Poppins", "Trebuchet MS", sans-serif;
+  --font-mono: "JetBrains Mono", "Fira Code", "Consolas", monospace;
 }
 
-@media (prefers-color-scheme: dark) {
+html {
-  :root {
+  scroll-behavior: smooth;
-    --background: #0a0a0a;
-    --foreground: #ededed;
-  }
 }
 
 body {
-  background: var(--background);
+  background:
+    radial-gradient(circle at 15% 0%, color-mix(in srgb, var(--unit-1) 9%, transparent), transparent 46%),
+    radial-gradient(circle at 90% 8%, color-mix(in srgb, var(--unit-3) 9%, transparent), transparent 34%),
+    radial-gradient(circle at 85% 88%, color-mix(in srgb, var(--unit-2) 7%, transparent), transparent 40%),
+    linear-gradient(180deg, #f7fbff 0%, var(--background) 100%);
   color: var(--foreground);
-  font-family: Arial, Helvetica, sans-serif;
+  font-family: var(--font-sans);
+  text-wrap: pretty;
+}
+
+h1,
+h2,
+h3,
+h4 {
+  font-family: var(--font-display);
+  letter-spacing: -0.02em;
+}
+
+::selection {
+  background: color-mix(in srgb, var(--unit-1) 20%, transparent);
+}
+
+/* Subtle gradient background pattern */
+.hero-gradient {
+  background:
+    radial-gradient(ellipse 100% 70% at 55% -15%, color-mix(in srgb, var(--unit-1) 14%, transparent), transparent),
+    radial-gradient(ellipse 70% 40% at 95% 45%, color-mix(in srgb, var(--unit-3) 12%, transparent), transparent),
+    radial-gradient(ellipse 70% 50% at 10% 75%, color-mix(in srgb, var(--unit-2) 10%, transparent), transparent),
+    linear-gradient(180deg, rgb(255 255 255 / 0.94), rgb(255 255 255 / 0.82));
+}
+
+/* Dot pattern overlay */
+.dot-pattern {
+  background-image:
+    linear-gradient(to right, rgb(203 218 239 / 0.45) 1px, transparent 1px),
+    linear-gradient(to bottom, rgb(203 218 239 / 0.45) 1px, transparent 1px);
+  background-size: 22px 22px;
+}
+
+@keyframes float-card {
+  0%,
+  100% {
+    transform: translateY(0);
+  }
+  50% {
+    transform: translateY(-3px);
+  }
+}
+
+.float-card {
+  animation: float-card 3.2s ease-in-out infinite;
+}
+
+.playground-bg {
+  background: linear-gradient(180deg, #2f65e8 0%, #2a5fdc 100%);
+}
+
+.playground-frame {
+  border-left: 4px solid #1e4fc6;
+  border-right: 4px solid #1e4fc6;
+  background: #ffffff;
+  box-shadow: 0 16px 40px rgb(15 35 86 / 0.22);
+}
+
+.section-ribbon {
+  border: 2px solid #1f4fbe;
+  background: linear-gradient(180deg, #2f65e8 0%, #2051c3 100%);
+  color: white;
+}
+
+.game-thumb-grid {
+  background-image:
+    linear-gradient(90deg, rgb(255 255 255 / 0.22) 1px, transparent 1px),
+    linear-gradient(0deg, rgb(255 255 255 / 0.22) 1px, transparent 1px);
+  background-size: 14px 14px;
+}
+
+/* Smooth scrollbar */
+::-webkit-scrollbar {
+  width: 6px;
+}
+
+::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+::-webkit-scrollbar-thumb {
+  background: var(--border);
+  border-radius: 3px;
+}
+
+::-webkit-scrollbar-thumb:hover {
+  background: var(--muted);
+}
+
+/* Focus ring utility */
+.focus-ring {
+  outline: 2px solid transparent;
+  outline-offset: 2px;
+}
+
+.focus-ring:focus-visible {
+  outline-color: var(--unit-1);
 }

app/layout.tsx

@@ -1,20 +1,10 @@
 import type { Metadata } from "next";
-import { Geist, Geist_Mono } from "next/font/google";
 import "./globals.css";
 
-const geistSans = Geist({
-  variable: "--font-geist-sans",
-  subsets: ["latin"],
-});
-
-const geistMono = Geist_Mono({
-  variable: "--font-geist-mono",
-  subsets: ["latin"],
-});
-
 export const metadata: Metadata = {
-  title: "Create Next App",
+  title: "Cabrits Math Lab",
-  description: "Generated by create next app",
+  description:
+    "Build confidence in mathematics with interactive lessons and practice for secondary school students.",
 };
 
 export default function RootLayout({
@@ -24,9 +14,7 @@ export default function RootLayout({
 }>) {
   return (
     <html lang="en">
-      <body
+      <body className="antialiased">
-        className={`${geistSans.variable} ${geistMono.variable} antialiased`}
-      >
         {children}
       </body>
     </html>

app/lessons/layout.tsx

@@ -0,0 +1,28 @@
+import { Header } from "@/components/layout/header";
+import { Footer } from "@/components/layout/footer";
+import { Sidebar } from "@/components/layout/sidebar";
+import { MobileNav } from "@/components/layout/mobile-nav";
+
+export default function LessonsLayout({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  return (
+    <div className="playground-bg flex min-h-screen flex-col">
+      <Header />
+      <div className="playground-frame relative mx-auto flex w-full max-w-6xl flex-1">
+        <Sidebar />
+        <main className="flex-1 bg-white">
+          <div className="relative p-4 lg:hidden">
+            <MobileNav />
+          </div>
+          <div className="mx-auto max-w-4xl px-4 py-8 sm:px-6 lg:px-8">
+            {children}
+          </div>
+        </main>
+      </div>
+      <Footer />
+    </div>
+  );
+}

app/lessons/page.tsx

@@ -0,0 +1,42 @@
+import Link from "next/link";
+import { curriculum } from "@/lib/curriculum";
+import { Card } from "@/components/ui/card";
+import { Badge } from "@/components/ui/badge";
+
+export default function LessonsOverview() {
+  return (
+    <div>
+      <h1 className="mb-2 text-3xl font-bold tracking-tight">All Topics</h1>
+      <p className="mb-10 text-muted">Form 1, Term 2 &mdash; Select a topic to explore</p>
+
+      {curriculum.map((unit) => (
+        <section key={unit.slug} className="mb-12">
+          <div className="mb-4 flex items-center gap-3">
+            <Badge variant={unit.color}>Unit {unit.number}</Badge>
+            <h2 className="text-xl font-semibold">{unit.title}</h2>
+            <span className="hidden text-sm text-muted sm:inline">{unit.weeks}</span>
+          </div>
+          <div className="grid gap-4 sm:grid-cols-2">
+            {unit.topics.map((topic) => (
+              <Link key={topic.slug} href={`/lessons/${unit.slug}/${topic.slug}`}>
+                <Card accent={unit.color} hover className="group h-full">
+                  <h3 className="mb-1 font-semibold">{topic.title}</h3>
+                  <p className="mb-3 text-sm leading-relaxed text-muted">{topic.description}</p>
+                  <div className="flex items-center justify-between text-xs text-muted">
+                    <span>Week {topic.week}</span>
+                    <span className="flex items-center gap-1 opacity-0 transition-opacity group-hover:opacity-100">
+                      Explore
+                      <svg className="h-3 w-3" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+                        <path strokeLinecap="round" strokeLinejoin="round" d="M9 5l7 7-7 7" />
+                      </svg>
+                    </span>
+                  </div>
+                </Card>
+              </Link>
+            ))}
+          </div>
+        </section>
+      ))}
+    </div>
+  );
+}

app/lessons/unit-1-fractions/add-subtract/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { FractionOperationExplorer } from "@/components/explorers/fraction-operation-explorer";
+
+export default function AddSubtractPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 1: Fractions", href: "/lessons/unit-1-fractions" },
+          { label: "Add & Subtract" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Add and Subtract Fractions</h1>
+
+      <FractionOperationExplorer />
+    </div>
+  );
+}

app/lessons/unit-1-fractions/divide/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { FractionOperationExplorer } from "@/components/explorers/fraction-operation-explorer";
+
+export default function DividePage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 1: Fractions", href: "/lessons/unit-1-fractions" },
+          { label: "Divide" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Divide Fractions</h1>
+
+      <FractionOperationExplorer />
+    </div>
+  );
+}

app/lessons/unit-1-fractions/fraction-of-quantity/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { FractionQuantityExplorer } from "@/components/explorers/fraction-quantity-explorer";
+
+export default function FractionOfQuantityPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 1: Fractions", href: "/lessons/unit-1-fractions" },
+          { label: "Of a Quantity" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Fraction of a Quantity</h1>
+
+      <FractionQuantityExplorer />
+    </div>
+  );
+}

app/lessons/unit-1-fractions/mixed-operations/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { BODMASExplorer } from "@/components/explorers/bodmas-explorer";
+
+export default function MixedOperationsPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 1: Fractions", href: "/lessons/unit-1-fractions" },
+          { label: "BODMAS" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Mixed Operations (BODMAS)</h1>
+
+      <BODMASExplorer />
+    </div>
+  );
+}

app/lessons/unit-1-fractions/multiply/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { FractionOperationExplorer } from "@/components/explorers/fraction-operation-explorer";
+
+export default function MultiplyPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 1: Fractions", href: "/lessons/unit-1-fractions" },
+          { label: "Multiply" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Multiply Fractions</h1>
+
+      <FractionOperationExplorer />
+    </div>
+  );
+}

app/lessons/unit-1-fractions/page.tsx

@@ -0,0 +1,41 @@
+import Link from "next/link";
+import { curriculum } from "@/lib/curriculum";
+import { Card } from "@/components/ui/card";
+import { Badge } from "@/components/ui/badge";
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+
+export default function Unit1Overview() {
+  const unit = curriculum[0];
+
+  return (
+    <div>
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: `Unit 1: ${unit.title}` },
+        ]}
+      />
+      <div className="mb-10">
+        <Badge variant="unit-1" className="mb-3">Unit 1 &mdash; {unit.weeks}</Badge>
+        <h1 className="mb-2 text-3xl font-bold tracking-tight">{unit.title}</h1>
+        <p className="text-muted leading-relaxed">{unit.description}</p>
+      </div>
+      <div className="grid gap-4 sm:grid-cols-2">
+        {unit.topics.map((topic, i) => (
+          <Link key={topic.slug} href={`/lessons/${unit.slug}/${topic.slug}`}>
+            <Card accent="unit-1" hover className="group h-full">
+              <div className="mb-2 flex items-center gap-2">
+                <span className="flex h-7 w-7 items-center justify-center rounded-lg bg-unit-1-light text-xs font-bold text-unit-1-dark shadow-[var(--shadow-sm)]">
+                  {i + 1}
+                </span>
+                <span className="text-xs text-muted">Week {topic.week}</span>
+              </div>
+              <h3 className="mb-1 font-semibold">{topic.title}</h3>
+              <p className="text-sm leading-relaxed text-muted">{topic.description}</p>
+            </Card>
+          </Link>
+        ))}
+      </div>
+    </div>
+  );
+}

app/lessons/unit-1-fractions/whole-from-fractions/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { FractionQuantityExplorer } from "@/components/explorers/fraction-quantity-explorer";
+
+export default function WholeFromFractionsPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 1: Fractions", href: "/lessons/unit-1-fractions" },
+          { label: "Find the Whole" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Calculate the Whole from Fractions</h1>
+
+      <FractionQuantityExplorer />
+    </div>
+  );
+}

app/lessons/unit-2-decimals/approximate/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { RoundingExplorer } from "@/components/explorers/rounding-explorer";
+
+export default function ApproximatePage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 2: Decimals", href: "/lessons/unit-2-decimals" },
+          { label: "Approximate" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Approximate Decimals</h1>
+
+      <RoundingExplorer />
+    </div>
+  );
+}

app/lessons/unit-2-decimals/compare-order/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { DecimalOrderExplorer } from "@/components/explorers/decimal-order-explorer";
+
+export default function CompareOrderPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 2: Decimals", href: "/lessons/unit-2-decimals" },
+          { label: "Compare & Order" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Compare and Order Decimals</h1>
+
+      <DecimalOrderExplorer />
+    </div>
+  );
+}

app/lessons/unit-2-decimals/page.tsx

@@ -0,0 +1,41 @@
+import Link from "next/link";
+import { curriculum } from "@/lib/curriculum";
+import { Card } from "@/components/ui/card";
+import { Badge } from "@/components/ui/badge";
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+
+export default function Unit2Overview() {
+  const unit = curriculum[1];
+
+  return (
+    <div>
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: `Unit 2: ${unit.title}` },
+        ]}
+      />
+      <div className="mb-10">
+        <Badge variant="unit-2" className="mb-3">Unit 2 &mdash; {unit.weeks}</Badge>
+        <h1 className="mb-2 text-3xl font-bold tracking-tight">{unit.title}</h1>
+        <p className="text-muted leading-relaxed">{unit.description}</p>
+      </div>
+      <div className="grid gap-4 sm:grid-cols-2">
+        {unit.topics.map((topic, i) => (
+          <Link key={topic.slug} href={`/lessons/${unit.slug}/${topic.slug}`}>
+            <Card accent="unit-2" hover className="group h-full">
+              <div className="mb-2 flex items-center gap-2">
+                <span className="flex h-7 w-7 items-center justify-center rounded-lg bg-unit-2-light text-xs font-bold text-unit-2-dark shadow-[var(--shadow-sm)]">
+                  {i + 7}
+                </span>
+                <span className="text-xs text-muted">Week {topic.week}</span>
+              </div>
+              <h3 className="mb-1 font-semibold">{topic.title}</h3>
+              <p className="text-sm leading-relaxed text-muted">{topic.description}</p>
+            </Card>
+          </Link>
+        ))}
+      </div>
+    </div>
+  );
+}

app/lessons/unit-2-decimals/standard-form/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { StandardFormExplorer } from "@/components/explorers/standard-form-explorer";
+
+export default function StandardFormPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 2: Decimals", href: "/lessons/unit-2-decimals" },
+          { label: "Standard Form" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Standard Form (Scientific Notation)</h1>
+
+      <StandardFormExplorer />
+    </div>
+  );
+}

app/lessons/unit-3-decimal-operations/add-subtract/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { DecimalArithmeticExplorer } from "@/components/explorers/decimal-arithmetic-explorer";
+
+export default function AddSubtractPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 3: Decimal Operations", href: "/lessons/unit-3-decimal-operations" },
+          { label: "Add & Subtract" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Add and Subtract Decimals</h1>
+
+      <DecimalArithmeticExplorer />
+    </div>
+  );
+}

app/lessons/unit-3-decimal-operations/convert/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { ConversionExplorer } from "@/components/explorers/conversion-explorer";
+
+export default function ConvertPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 3: Decimal Operations", href: "/lessons/unit-3-decimal-operations" },
+          { label: "Convert" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Convert Decimals and Fractions</h1>
+
+      <ConversionExplorer />
+    </div>
+  );
+}

app/lessons/unit-3-decimal-operations/multiply-divide/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { DecimalArithmeticExplorer } from "@/components/explorers/decimal-arithmetic-explorer";
+
+export default function MultiplyDividePage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 3: Decimal Operations", href: "/lessons/unit-3-decimal-operations" },
+          { label: "Multiply & Divide" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Multiply and Divide Decimals</h1>
+
+      <DecimalArithmeticExplorer />
+    </div>
+  );
+}

app/lessons/unit-3-decimal-operations/page.tsx

@@ -0,0 +1,41 @@
+import Link from "next/link";
+import { curriculum } from "@/lib/curriculum";
+import { Card } from "@/components/ui/card";
+import { Badge } from "@/components/ui/badge";
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+
+export default function Unit3Overview() {
+  const unit = curriculum[2];
+
+  return (
+    <div>
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: `Unit 3: ${unit.title}` },
+        ]}
+      />
+      <div className="mb-10">
+        <Badge variant="unit-3" className="mb-3">Unit 3 &mdash; {unit.weeks}</Badge>
+        <h1 className="mb-2 text-3xl font-bold tracking-tight">{unit.title}</h1>
+        <p className="text-muted leading-relaxed">{unit.description}</p>
+      </div>
+      <div className="grid gap-4 sm:grid-cols-2">
+        {unit.topics.map((topic, i) => (
+          <Link key={topic.slug} href={`/lessons/${unit.slug}/${topic.slug}`}>
+            <Card accent="unit-3" hover className="group h-full">
+              <div className="mb-2 flex items-center gap-2">
+                <span className="flex h-7 w-7 items-center justify-center rounded-lg bg-unit-3-light text-xs font-bold text-unit-3-dark shadow-[var(--shadow-sm)]">
+                  {i + 10}
+                </span>
+                <span className="text-xs text-muted">Week {topic.week}</span>
+              </div>
+              <h3 className="mb-1 font-semibold">{topic.title}</h3>
+              <p className="text-sm leading-relaxed text-muted">{topic.description}</p>
+            </Card>
+          </Link>
+        ))}
+      </div>
+    </div>
+  );
+}

app/lessons/unit-4-ratio-proportion/define-ratio/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { RatioExplorer } from "@/components/explorers/ratio-explorer";
+
+export default function DefineRatioPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 4: Ratio & Proportion", href: "/lessons/unit-4-ratio-proportion" },
+          { label: "Define Ratio" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Define a Ratio</h1>
+
+      <RatioExplorer />
+    </div>
+  );
+}

app/lessons/unit-4-ratio-proportion/divide-in-ratio/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { RatioExplorer } from "@/components/explorers/ratio-explorer";
+
+export default function DivideInRatioPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 4: Ratio & Proportion", href: "/lessons/unit-4-ratio-proportion" },
+          { label: "Divide in Ratio" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Divide a Quantity in a Given Ratio</h1>
+
+      <RatioExplorer />
+    </div>
+  );
+}

app/lessons/unit-4-ratio-proportion/fractions-and-ratios/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { RatioExplorer } from "@/components/explorers/ratio-explorer";
+
+export default function FractionsAndRatiosPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 4: Ratio & Proportion", href: "/lessons/unit-4-ratio-proportion" },
+          { label: "Fractions & Ratios" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Fractions and Ratios</h1>
+
+      <RatioExplorer />
+    </div>
+  );
+}

app/lessons/unit-4-ratio-proportion/page.tsx

@@ -0,0 +1,41 @@
+import Link from "next/link";
+import { curriculum } from "@/lib/curriculum";
+import { Card } from "@/components/ui/card";
+import { Badge } from "@/components/ui/badge";
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+
+export default function Unit4Overview() {
+  const unit = curriculum[3];
+
+  return (
+    <div>
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: `Unit 4: ${unit.title}` },
+        ]}
+      />
+      <div className="mb-10">
+        <Badge variant="unit-4" className="mb-3">Unit 4 &mdash; {unit.weeks}</Badge>
+        <h1 className="mb-2 text-3xl font-bold tracking-tight">{unit.title}</h1>
+        <p className="text-muted leading-relaxed">{unit.description}</p>
+      </div>
+      <div className="grid gap-4 sm:grid-cols-2">
+        {unit.topics.map((topic, i) => (
+          <Link key={topic.slug} href={`/lessons/${unit.slug}/${topic.slug}`}>
+            <Card accent="unit-4" hover className="group h-full">
+              <div className="mb-2 flex items-center gap-2">
+                <span className="flex h-7 w-7 items-center justify-center rounded-lg bg-unit-4-light text-xs font-bold text-unit-4-dark shadow-[var(--shadow-sm)]">
+                  {String.fromCharCode(97 + i)}
+                </span>
+                <span className="text-xs text-muted">Week {topic.week}</span>
+              </div>
+              <h3 className="mb-1 font-semibold">{topic.title}</h3>
+              <p className="text-sm leading-relaxed text-muted">{topic.description}</p>
+            </Card>
+          </Link>
+        ))}
+      </div>
+    </div>
+  );
+}

app/lessons/unit-4-ratio-proportion/simplify-ratios/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { RatioExplorer } from "@/components/explorers/ratio-explorer";
+
+export default function SimplifyRatiosPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 4: Ratio & Proportion", href: "/lessons/unit-4-ratio-proportion" },
+          { label: "Simplify Ratios" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Simplify Ratios</h1>
+
+      <RatioExplorer />
+    </div>
+  );
+}

app/lessons/unit-4-ratio-proportion/word-problems/page.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import { Breadcrumbs } from "@/components/layout/breadcrumbs";
+import { RatioExplorer } from "@/components/explorers/ratio-explorer";
+
+export default function WordProblemsPage() {
+  return (
+    <div className="space-y-8">
+      <Breadcrumbs
+        items={[
+          { label: "Lessons", href: "/lessons" },
+          { label: "Unit 4: Ratio & Proportion", href: "/lessons/unit-4-ratio-proportion" },
+          { label: "Word Problems" },
+        ]}
+      />
+
+      <h1 className="text-3xl font-bold tracking-tight">Proportional Parts Word Problems</h1>
+
+      <RatioExplorer />
+    </div>
+  );
+}

app/not-found.tsx

@@ -0,0 +1,37 @@
+import Link from "next/link";
+import { Header } from "@/components/layout/header";
+import { Footer } from "@/components/layout/footer";
+
+export default function NotFound() {
+  return (
+    <div className="playground-bg flex min-h-screen flex-col">
+      <Header />
+      <main className="playground-frame hero-gradient relative mx-auto flex w-full max-w-6xl flex-1 items-center justify-center">
+        <div className="dot-pattern absolute inset-0 opacity-25" />
+        <div className="relative text-center">
+          <p className="mb-2 text-sm font-semibold uppercase tracking-widest text-muted">
+            Page not found
+          </p>
+          <h1 className="mb-4 text-8xl font-bold tracking-tighter">
+            <span className="bg-gradient-to-r from-unit-1 via-unit-4 to-unit-2 bg-clip-text text-transparent">
+              404
+            </span>
+          </h1>
+          <p className="mb-8 text-lg text-muted">
+            This page doesn&apos;t exist or has been moved.
+          </p>
+          <Link
+            href="/"
+            className="inline-flex items-center gap-2 rounded-xl bg-foreground px-6 py-3 font-medium text-background shadow-[var(--shadow-md)] transition-all duration-200 hover:shadow-[var(--shadow-lg)] hover:-translate-y-0.5"
+          >
+            <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+              <path strokeLinecap="round" strokeLinejoin="round" d="M10 19l-7-7m0 0l7-7m-7 7h18" />
+            </svg>
+            Back to Home
+          </Link>
+        </div>
+      </main>
+      <Footer />
+    </div>
+  );
+}

app/page.tsx

@@ -1,65 +1,133 @@
-import Image from "next/image";
+import Link from "next/link";
+import { Header } from "@/components/layout/header";
+import { Footer } from "@/components/layout/footer";
+import { curriculum } from "@/lib/curriculum";
+
+const unitStyles = {
+  "unit-1": {
+    tile: "from-[#4e95ff] to-[#1f63ea]",
+    unitCard: "border-[#8cb2ff] bg-[#eaf2ff]",
+    chip: "bg-[#2059cc]",
+  },
+  "unit-2": {
+    tile: "from-[#29c6c5] to-[#0f8d8c]",
+    unitCard: "border-[#89e5dd] bg-[#eafffb]",
+    chip: "bg-[#0f8d8c]",
+  },
+  "unit-3": {
+    tile: "from-[#ffab55] to-[#e97617]",
+    unitCard: "border-[#ffd2a3] bg-[#fff4e8]",
+    chip: "bg-[#d26a17]",
+  },
+  "unit-4": {
+    tile: "from-[#ff5f85] to-[#d11b56]",
+    unitCard: "border-[#ffb2c7] bg-[#fff0f4]",
+    chip: "bg-[#c6174e]",
+  },
+};
+
+const topicTiles = [
+  "from-[#4e95ff] via-[#357fe9] to-[#1f63ea]",
+  "from-[#2ac3be] via-[#1da8a3] to-[#0f8d8c]",
+  "from-[#ffb067] via-[#f2913a] to-[#d86e16]",
+  "from-[#ff6f98] via-[#ef3d72] to-[#cb1c54]",
+  "from-[#7d95ff] via-[#6078f2] to-[#3f56d9]",
+  "from-[#4ccf7b] via-[#2fb45f] to-[#1f944b]",
+  "from-[#ff8f8f] via-[#f26b6b] to-[#d94545]",
+  "from-[#5eb7ff] via-[#3f99ef] to-[#2a7fda]",
+];
 
 export default function Home() {
+  const allTopics = curriculum.flatMap((unit) =>
+    unit.topics.map((topic) => ({
+      unit,
+      topic,
+    })),
+  );
+
   return (
-    <div className="flex min-h-screen items-center justify-center bg-zinc-50 font-sans dark:bg-black">
+    <div className="playground-bg flex min-h-screen flex-col">
-      <main className="flex min-h-screen w-full max-w-3xl flex-col items-center justify-between py-32 px-16 bg-white dark:bg-black sm:items-start">
+      <Header />
-        <Image
+      <main className="playground-frame mx-auto w-full max-w-6xl flex-1 px-3 pb-10 sm:px-5">
-          className="dark:invert"
+        <section className="mt-4 rounded-md border-2 border-[#1f50bf] bg-[#f1f6ff] p-4 sm:p-6">
-          src="/next.svg"
+          <p className="text-center text-sm font-bold text-[#26438b]">
-          alt="Next.js logo"
+            Interactive maths practice for secondary school students
-          width={100}
-          height={20}
-          priority
-        />
-        <div className="flex flex-col items-center gap-6 text-center sm:items-start sm:text-left">
-          <h1 className="max-w-xs text-3xl font-semibold leading-10 tracking-tight text-black dark:text-zinc-50">
-            To get started, edit the page.tsx file.
-          </h1>
-          <p className="max-w-md text-lg leading-8 text-zinc-600 dark:text-zinc-400">
-            Looking for a starting point or more instructions? Head over to{" "}
-            <a
-              href="https://vercel.com/templates?framework=next.js&utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-              className="font-medium text-zinc-950 dark:text-zinc-50"
-            >
-              Templates
-            </a>{" "}
-            or the{" "}
-            <a
-              href="https://nextjs.org/learn?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-              className="font-medium text-zinc-950 dark:text-zinc-50"
-            >
-              Learning
-            </a>{" "}
-            center.
           </p>
-        </div>
+          <h1 className="mt-2 text-center text-3xl font-extrabold text-[#17367d] sm:text-5xl">
-        <div className="flex flex-col gap-4 text-base font-medium sm:flex-row">
+            Math Topics Students Love to Explore
-          <a
+          </h1>
-            className="flex h-12 w-full items-center justify-center gap-2 rounded-full bg-foreground px-5 text-background transition-colors hover:bg-[#383838] dark:hover:bg-[#ccc] md:w-[158px]"
+          <p className="mx-auto mt-3 max-w-3xl text-center text-sm font-semibold text-[#33508e] sm:text-base">
-            href="https://vercel.com/new?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
+            Explore each topic with visual examples, short explanations, and guided lessons.
-            target="_blank"
+            Pick a unit, jump into a topic, and start solving.
-            rel="noopener noreferrer"
+          </p>
+          <div className="mt-5 flex flex-wrap items-center justify-center gap-3">
+            <Link
+              href="/lessons"
+              className="rounded-sm bg-[#e6503e] px-5 py-2.5 text-sm font-extrabold text-white shadow-md transition-colors hover:bg-[#cc4231]"
             >
-            <Image
+              Browse Lessons
-              className="dark:invert"
+            </Link>
-              src="/vercel.svg"
+            <Link
-              alt="Vercel logomark"
+              href="/practice"
-              width={16}
+              className="rounded-sm bg-[#0e9d50] px-5 py-2.5 text-sm font-extrabold text-white shadow-md transition-colors hover:bg-[#0c7f41]"
-              height={16}
-            />
-            Deploy Now
-          </a>
-          <a
-            className="flex h-12 w-full items-center justify-center rounded-full border border-solid border-black/[.08] px-5 transition-colors hover:border-transparent hover:bg-black/[.04] dark:border-white/[.145] dark:hover:bg-[#1a1a1a] md:w-[158px]"
-            href="https://nextjs.org/docs?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
             >
-            Documentation
+              Start Practice
-          </a>
+            </Link>
           </div>
+        </section>
+
+        <section className="mt-5">
+          <h2 className="section-ribbon rounded-sm px-3 py-2 text-lg font-extrabold sm:text-xl">
+            Unit Worlds
+          </h2>
+          <div className="mt-3 grid gap-3 sm:grid-cols-2 lg:grid-cols-4">
+            {curriculum.map((unit) => (
+              <Link
+                key={unit.slug}
+                href={`/lessons/${unit.slug}`}
+                className={`rounded-md border-2 p-3 transition-transform hover:-translate-y-0.5 ${unitStyles[unit.color].unitCard}`}
+              >
+                <div className="flex items-center justify-between gap-2">
+                  <h3 className="text-lg font-extrabold text-[#142f75]">{unit.title}</h3>
+                  <span className={`rounded-full px-2 py-1 text-xs font-extrabold text-white ${unitStyles[unit.color].chip}`}>
+                    Unit {unit.number}
+                  </span>
+                </div>
+                <p className="mt-2 text-sm font-semibold text-[#35508b]">{unit.description}</p>
+                <p className="mt-2 text-xs font-bold uppercase tracking-wide text-[#4262aa]">{unit.weeks}</p>
+              </Link>
+            ))}
+          </div>
+        </section>
+
+        <section className="mt-6">
+          <h2 className="section-ribbon rounded-sm px-3 py-2 text-lg font-extrabold sm:text-xl">
+            Topic Explorer
+          </h2>
+          <div className="mt-3 grid grid-cols-2 gap-2.5 sm:grid-cols-3 md:grid-cols-4 lg:grid-cols-5">
+            {allTopics.map(({ unit, topic }, index) => (
+              <Link
+                key={`${unit.slug}-${topic.slug}`}
+                href={`/lessons/${unit.slug}/${topic.slug}`}
+                className="rounded-sm border border-[#8ea9df] bg-white p-2 transition-transform hover:-translate-y-0.5 hover:shadow-md"
+              >
+                <div className={`game-thumb-grid mb-2 flex aspect-[4/3] flex-col justify-between rounded-sm bg-gradient-to-br p-2 text-white ${topicTiles[index % topicTiles.length]}`}>
+                  <span className="w-fit rounded-sm bg-black/25 px-1.5 py-0.5 text-[10px] font-extrabold uppercase tracking-wide">
+                    Week {topic.week}
+                  </span>
+                  <span className="text-center text-xs font-extrabold leading-tight">
+                    {topic.shortTitle}
+                  </span>
+                </div>
+                <p className="min-h-[2.5rem] text-xs font-extrabold text-[#193981]">
+                  {topic.title}
+                </p>
+              </Link>
+            ))}
+          </div>
+        </section>
       </main>
+      <Footer />
     </div>
   );
 }

app/practice/page.tsx

@@ -0,0 +1,160 @@
+"use client";
+
+import { useState } from "react";
+import { Card } from "@/components/ui/card";
+import { Button } from "@/components/ui/button";
+import { Badge } from "@/components/ui/badge";
+import { Header } from "@/components/layout/header";
+import { Footer } from "@/components/layout/footer";
+import { PracticeSection } from "@/components/practice/practice-section";
+import type { Difficulty, MathProblem } from "@/lib/problems/types";
+
+import { generateFractionAddSubtract, generateFractionMultiply, generateFractionDivide, generateFractionOfQuantity, generateWholeFromFraction } from "@/lib/problems/generators/fraction-problems";
+import { generateDecimalCompareOrder, generateDecimalRounding, generateStandardForm, generateDecimalAddSubtract, generateDecimalMultiplyDivide, generateDecimalConversion } from "@/lib/problems/generators/decimal-problems";
+import { generateSimplifyRatio, generateDivideInRatio, generateRatioWordProblem } from "@/lib/problems/generators/ratio-problems";
+
+interface TopicGenerator {
+  unitSlug: string;
+  topicSlug: string;
+  label: string;
+  generator: (difficulty: Difficulty) => MathProblem;
+  unitColor: "unit-1" | "unit-2" | "unit-3" | "unit-4";
+}
+
+type UnitColor = TopicGenerator["unitColor"];
+
+const TOPIC_GENERATORS: TopicGenerator[] = [
+  { unitSlug: "unit-1-fractions", topicSlug: "add-subtract", label: "Add & Subtract Fractions", generator: generateFractionAddSubtract, unitColor: "unit-1" },
+  { unitSlug: "unit-1-fractions", topicSlug: "multiply", label: "Multiply Fractions", generator: generateFractionMultiply, unitColor: "unit-1" },
+  { unitSlug: "unit-1-fractions", topicSlug: "divide", label: "Divide Fractions", generator: generateFractionDivide, unitColor: "unit-1" },
+  { unitSlug: "unit-1-fractions", topicSlug: "fraction-of-quantity", label: "Fraction of a Quantity", generator: generateFractionOfQuantity, unitColor: "unit-1" },
+  { unitSlug: "unit-1-fractions", topicSlug: "whole-from-fractions", label: "Find the Whole", generator: generateWholeFromFraction, unitColor: "unit-1" },
+  { unitSlug: "unit-2-decimals", topicSlug: "compare-order", label: "Compare & Order Decimals", generator: generateDecimalCompareOrder, unitColor: "unit-2" },
+  { unitSlug: "unit-2-decimals", topicSlug: "approximate", label: "Approximate Decimals", generator: generateDecimalRounding, unitColor: "unit-2" },
+  { unitSlug: "unit-2-decimals", topicSlug: "standard-form", label: "Standard Form", generator: generateStandardForm, unitColor: "unit-2" },
+  { unitSlug: "unit-3-decimal-operations", topicSlug: "convert", label: "Convert Decimals & Fractions", generator: generateDecimalConversion, unitColor: "unit-3" },
+  { unitSlug: "unit-3-decimal-operations", topicSlug: "add-subtract", label: "Add & Subtract Decimals", generator: generateDecimalAddSubtract, unitColor: "unit-3" },
+  { unitSlug: "unit-3-decimal-operations", topicSlug: "multiply-divide", label: "Multiply & Divide Decimals", generator: generateDecimalMultiplyDivide, unitColor: "unit-3" },
+  { unitSlug: "unit-4-ratio-proportion", topicSlug: "simplify-ratios", label: "Simplify Ratios", generator: generateSimplifyRatio, unitColor: "unit-4" },
+  { unitSlug: "unit-4-ratio-proportion", topicSlug: "divide-in-ratio", label: "Divide in a Ratio", generator: generateDivideInRatio, unitColor: "unit-4" },
+  { unitSlug: "unit-4-ratio-proportion", topicSlug: "word-problems", label: "Ratio Word Problems", generator: generateRatioWordProblem, unitColor: "unit-4" },
+];
+
+const unitColors: Record<UnitColor, { activeFilter: string; inactiveFilter: string; label: string }> = {
+  "unit-1": {
+    activeFilter: "border-unit-1 bg-unit-1 text-white shadow-[var(--shadow-sm)]",
+    inactiveFilter: "border-unit-1/40 text-unit-1-dark hover:bg-unit-1-light",
+    label: "Fractions",
+  },
+  "unit-2": {
+    activeFilter: "border-unit-2 bg-unit-2 text-white shadow-[var(--shadow-sm)]",
+    inactiveFilter: "border-unit-2/40 text-unit-2-dark hover:bg-unit-2-light",
+    label: "Decimals",
+  },
+  "unit-3": {
+    activeFilter: "border-unit-3 bg-unit-3 text-white shadow-[var(--shadow-sm)]",
+    inactiveFilter: "border-unit-3/40 text-unit-3-dark hover:bg-unit-3-light",
+    label: "Decimal Operations",
+  },
+  "unit-4": {
+    activeFilter: "border-unit-4 bg-unit-4 text-white shadow-[var(--shadow-sm)]",
+    inactiveFilter: "border-unit-4/40 text-unit-4-dark hover:bg-unit-4-light",
+    label: "Ratio & Proportion",
+  },
+};
+
+export default function PracticePage() {
+  const [selectedTopic, setSelectedTopic] = useState<TopicGenerator | null>(null);
+  const [filterUnit, setFilterUnit] = useState<UnitColor | null>(null);
+
+  const filtered = filterUnit
+    ? TOPIC_GENERATORS.filter((t) => t.unitColor === filterUnit)
+    : TOPIC_GENERATORS;
+
+  return (
+    <div className="playground-bg flex min-h-screen flex-col">
+      <Header />
+      <main className="playground-frame mx-auto w-full max-w-6xl flex-1 bg-white">
+        <div className="mx-auto max-w-4xl px-4 py-8 sm:px-6 lg:px-8">
+          <h1 className="mb-2 text-3xl font-extrabold tracking-tight">Practice</h1>
+          <p className="mb-8 text-muted">
+            Pick a topic and build your confidence with fresh questions each round.
+          </p>
+
+          {/* Unit filters */}
+          <div className="mb-6 flex flex-wrap gap-2">
+            <button
+              onClick={() => setFilterUnit(null)}
+              className={`rounded-full border-2 px-4 py-1.5 text-sm font-extrabold transition-all duration-200 ${
+                filterUnit === null
+                  ? "border-foreground bg-foreground text-background shadow-[var(--shadow-sm)]"
+                  : "border-border text-muted hover:text-foreground"
+              }`}
+            >
+              All Topics
+            </button>
+            {(["unit-1", "unit-2", "unit-3", "unit-4"] as const).map((uc) => (
+              <button
+                key={uc}
+                onClick={() => setFilterUnit(filterUnit === uc ? null : uc)}
+                className={`rounded-full border-2 px-4 py-1.5 text-sm font-extrabold transition-all duration-200 ${
+                  filterUnit === uc
+                    ? unitColors[uc].activeFilter
+                    : unitColors[uc].inactiveFilter
+                }`}
+              >
+                {unitColors[uc].label}
+              </button>
+            ))}
+          </div>
+
+          {/* Topic grid */}
+          {!selectedTopic && (
+            <div className="grid gap-4 sm:grid-cols-2">
+              {filtered.map((topic) => (
+                <Card
+                  key={`${topic.unitSlug}-${topic.topicSlug}`}
+                  hover
+                  className="cursor-pointer"
+                  accent={topic.unitColor}
+                  onClick={() => setSelectedTopic(topic)}
+                >
+                  <div className="flex items-center justify-between">
+                    <span className="font-bold">{topic.label}</span>
+                    <Badge variant={topic.unitColor}>
+                      {unitColors[topic.unitColor].label}
+                    </Badge>
+                  </div>
+                </Card>
+              ))}
+            </div>
+          )}
+
+          {/* Practice area */}
+          {selectedTopic && (
+            <div>
+              <Button
+                variant="secondary"
+                size="sm"
+                onClick={() => setSelectedTopic(null)}
+                className="mb-6"
+              >
+                <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+                  <path strokeLinecap="round" strokeLinejoin="round" d="M10 19l-7-7m0 0l7-7m-7 7h18" />
+                </svg>
+                Back to Topics
+              </Button>
+
+              <PracticeSection
+                title={`Practice: ${selectedTopic.label}`}
+                generator={selectedTopic.generator}
+                unitColor={selectedTopic.unitColor}
+              />
+            </div>
+          )}
+        </div>
+      </main>
+      <Footer />
+    </div>
+  );
+}

components/explorers/bodmas-explorer.tsx

@@ -0,0 +1,338 @@
+"use client";
+
+import { useState } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+import { MathDisplay } from "@/components/math/math-display";
+import { toKatex, simplify, add, subtract, multiply, divide } from "@/lib/math/fractions";
+
+interface FractionVal {
+  num: number;
+  den: number;
+}
+
+interface Expression {
+  fractions: FractionVal[];
+  operators: string[];
+}
+
+interface Step {
+  label: string;
+  math: string;
+  highlightIndex: number | null; // which operator is being evaluated
+}
+
+const OP_PRIORITY: Record<string, number> = {
+  "×": 2,
+  "÷": 2,
+  "+": 1,
+  "−": 1,
+};
+
+function performOp(a: FractionVal, b: FractionVal, op: string): FractionVal {
+  let result: [number, number];
+  switch (op) {
+    case "+":
+      result = add(a.num, a.den, b.num, b.den);
+      break;
+    case "−":
+      result = subtract(a.num, a.den, b.num, b.den);
+      break;
+    case "×":
+      result = multiply(a.num, a.den, b.num, b.den);
+      break;
+    case "÷":
+      result = divide(a.num, a.den, b.num, b.den);
+      break;
+    default:
+      result = [0, 1];
+  }
+  return { num: result[0], den: result[1] };
+}
+
+function expressionToKatex(fracs: FractionVal[], ops: string[], highlightIdx: number | null): string {
+  const parts: string[] = [];
+  fracs.forEach((f, i) => {
+    parts.push(toKatex(f.num, f.den));
+    if (i < ops.length) {
+      if (i === highlightIdx) {
+        parts.push(`\\;\\boxed{${ops[i]}}\\;`);
+      } else {
+        parts.push(`\\;${ops[i]}\\;`);
+      }
+    }
+  });
+  return parts.join("");
+}
+
+function buildBodmasSteps(expr: Expression): Step[] {
+  const steps: Step[] = [];
+  let fracs = [...expr.fractions];
+  let ops = [...expr.operators];
+
+  // Step 0: Show the expression
+  steps.push({
+    label: "Start with the expression",
+    math: expressionToKatex(fracs, ops, null),
+    highlightIndex: null,
+  });
+
+  while (ops.length > 0) {
+    // Find highest priority operator (leftmost if tie)
+    let maxPri = 0;
+    let opIdx = 0;
+    ops.forEach((op, i) => {
+      if (OP_PRIORITY[op] > maxPri) {
+        maxPri = OP_PRIORITY[op];
+        opIdx = i;
+      }
+    });
+
+    // Highlight the operation to perform
+    steps.push({
+      label: `BODMAS: do ${ops[opIdx]} first (${OP_PRIORITY[ops[opIdx]] === 2 ? "multiplication/division" : "addition/subtraction"})`,
+      math: expressionToKatex(fracs, ops, opIdx),
+      highlightIndex: opIdx,
+    });
+
+    // Perform the operation
+    const result = performOp(fracs[opIdx], fracs[opIdx + 1], ops[opIdx]);
+    const [sn, sd] = simplify(result.num, result.den);
+
+    const newFracs = [...fracs];
+    newFracs.splice(opIdx, 2, { num: sn, den: sd });
+    const newOps = [...ops];
+    newOps.splice(opIdx, 1);
+
+    steps.push({
+      label: `${fracs[opIdx].num}/${fracs[opIdx].den} ${ops[opIdx]} ${fracs[opIdx + 1].num}/${fracs[opIdx + 1].den} = ${sn}/${sd}`,
+      math: expressionToKatex(newFracs, newOps, null),
+      highlightIndex: null,
+    });
+
+    fracs = newFracs;
+    ops = newOps;
+  }
+
+  return steps;
+}
+
+const PRESETS: { label: string; fracs: FractionVal[]; ops: string[] }[] = [
+  {
+    label: "½ + ¼ × ⅗",
+    fracs: [
+      { num: 1, den: 2 },
+      { num: 1, den: 4 },
+      { num: 3, den: 5 },
+    ],
+    ops: ["+", "×"],
+  },
+  {
+    label: "⅔ × ¾ − ½",
+    fracs: [
+      { num: 2, den: 3 },
+      { num: 3, den: 4 },
+      { num: 1, den: 2 },
+    ],
+    ops: ["×", "−"],
+  },
+  {
+    label: "⅗ ÷ ¼ + ⅔",
+    fracs: [
+      { num: 3, den: 5 },
+      { num: 1, den: 4 },
+      { num: 2, den: 3 },
+    ],
+    ops: ["÷", "+"],
+  },
+];
+
+export function BODMASExplorer() {
+  const [fracs, setFracs] = useState<FractionVal[]>([
+    { num: 1, den: 2 },
+    { num: 1, den: 4 },
+    { num: 3, den: 5 },
+  ]);
+  const [ops, setOps] = useState<string[]>(["+", "×"]);
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function updateFrac(idx: number, field: "num" | "den", value: string) {
+    setFracs((prev) => {
+      const next = [...prev];
+      next[idx] = { ...next[idx], [field]: parseInt(value) || 0 };
+      return next;
+    });
+  }
+
+  function handleGo() {
+    setError("");
+    if (fracs.some((f) => f.den === 0)) {
+      setError("Denominators cannot be zero.");
+      return;
+    }
+    if (fracs.some((f) => Math.abs(f.num) > 99 || Math.abs(f.den) > 99)) {
+      setError("Keep numbers under 100.");
+      return;
+    }
+    try {
+      const s = buildBodmasSteps({ fractions: fracs, operators: ops });
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not compute. Check your inputs.");
+    }
+  }
+
+  function loadPreset(idx: number) {
+    const p = PRESETS[idx];
+    setFracs([...p.fracs]);
+    setOps([...p.ops]);
+    reset();
+  }
+
+  function stepForward() {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }
+
+  function stepBack() {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }
+
+  function togglePlay() {
+    setIsPlaying((p) => !p);
+  }
+
+  function reset() {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }
+
+  const step = steps ? steps[currentStep] : null;
+
+  const opChoices = ["+", "−", "×", "÷"];
+
+  return (
+    <div className="space-y-4">
+      {/* Presets */}
+      <div className="flex flex-wrap gap-2">
+        {PRESETS.map((p, i) => (
+          <button
+            key={i}
+            onClick={() => loadPreset(i)}
+            className="rounded-full border-2 border-unit-1/40 px-4 py-2 text-sm font-semibold text-unit-1 transition-colors hover:bg-unit-1-light"
+          >
+            {p.label}
+          </button>
+        ))}
+      </div>
+
+      {/* Input */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-1">
+          Enter a BODMAS expression with fractions
+        </p>
+        <div className="flex flex-wrap items-center gap-2">
+          {fracs.map((f, i) => (
+            <div key={i} className="flex items-center gap-2">
+              <div className="flex flex-col items-center">
+                <input
+                  type="number"
+                  value={f.num || ""}
+                  onChange={(e) => updateFrac(i, "num", e.target.value)}
+                  className="w-12 rounded-lg border-2 border-border bg-surface px-1.5 py-1 text-center text-base font-bold outline-none focus:border-unit-1"
+                  aria-label={`Numerator ${i + 1}`}
+                />
+                <div className="my-0.5 h-0.5 w-10 bg-foreground" />
+                <input
+                  type="number"
+                  value={f.den || ""}
+                  onChange={(e) => updateFrac(i, "den", e.target.value)}
+                  className="w-12 rounded-lg border-2 border-border bg-surface px-1.5 py-1 text-center text-base font-bold outline-none focus:border-unit-1"
+                  aria-label={`Denominator ${i + 1}`}
+                />
+              </div>
+              {i < ops.length && (
+                <select
+                  value={ops[i]}
+                  onChange={(e) => {
+                    const next = [...ops];
+                    next[i] = e.target.value;
+                    setOps(next);
+                  }}
+                  className="rounded-lg border-2 border-border bg-surface px-2 py-2 text-center text-lg font-bold text-foreground outline-none focus:border-unit-1"
+                >
+                  {opChoices.map((o) => (
+                    <option key={o} value={o}>
+                      {o}
+                    </option>
+                  ))}
+                </select>
+              )}
+            </div>
+          ))}
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-1 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-1-dark"
+          >
+            Go →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display */}
+      <Card className="flex min-h-[200px] flex-col items-center justify-center gap-4 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter an expression above and click <strong>Go</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            <MathDisplay math={step.math} className="text-2xl" />
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !steps ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Final Answer</p>
+            <div className="text-3xl font-extrabold max-sm:text-2xl">
+              <MathDisplay math={steps[steps.length - 1].math} />
+            </div>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/conversion-explorer.tsx

@@ -0,0 +1,345 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+import { MathDisplay } from "@/components/math/math-display";
+import { simplify, toKatex, gcd } from "@/lib/math/fractions";
+
+type ConvertMode = "decToFrac" | "fracToDec";
+
+interface Step {
+  label: string;
+  math: string;
+  gridFilled?: number; // out of 100 for decimal grid
+  barFilled?: number;
+  barTotal?: number;
+}
+
+function buildDecToFracSteps(decimal: string): Step[] {
+  const steps: Step[] = [];
+  const val = parseFloat(decimal);
+
+  steps.push({
+    label: `Convert ${decimal} to a fraction`,
+    math: `${decimal} = \\;?`,
+    gridFilled: Math.round(val * 100),
+  });
+
+  // Count decimal places
+  const parts = decimal.split(".");
+  const decPlaces = parts[1]?.length || 0;
+  const denominator = Math.pow(10, decPlaces);
+  const numerator = Math.round(val * denominator);
+
+  steps.push({
+    label: `${decPlaces} decimal place${decPlaces !== 1 ? "s" : ""} → denominator is ${denominator}`,
+    math: `${decimal} = ${toKatex(numerator, denominator)}`,
+    gridFilled: Math.round(val * 100),
+    barFilled: numerator,
+    barTotal: denominator,
+  });
+
+  // Simplify
+  const [sn, sd] = simplify(numerator, denominator);
+  if (sn !== numerator || sd !== denominator) {
+    const g = gcd(numerator, denominator);
+    steps.push({
+      label: `Simplify by dividing by GCD = ${g}`,
+      math: `${toKatex(numerator, denominator)} = ${toKatex(sn, sd)}`,
+      gridFilled: Math.round(val * 100),
+      barFilled: sn,
+      barTotal: sd,
+    });
+  }
+
+  steps.push({
+    label: `Result: ${decimal} = ${sn}/${sd}`,
+    math: `${decimal} = ${toKatex(sn, sd)}`,
+    gridFilled: Math.round(val * 100),
+    barFilled: sn,
+    barTotal: sd,
+  });
+
+  return steps;
+}
+
+function buildFracToDecSteps(num: number, den: number): Step[] {
+  const steps: Step[] = [];
+
+  steps.push({
+    label: `Convert ${num}/${den} to a decimal`,
+    math: `${toKatex(num, den)} = \\;?`,
+    barFilled: num,
+    barTotal: den,
+  });
+
+  // Step: Perform the division
+  const result = num / den;
+  const resultStr = Number.isInteger(result) ? result.toString() : result.toFixed(6).replace(/0+$/, "");
+
+  steps.push({
+    label: `Divide numerator by denominator`,
+    math: `${num} \\div ${den} = ${resultStr}`,
+    barFilled: num,
+    barTotal: den,
+    gridFilled: Math.min(100, Math.round(result * 100)),
+  });
+
+  // Check for terminating vs repeating
+  let tempDen = den;
+  const [, simpDen] = simplify(num, den);
+  tempDen = simpDen;
+  // Remove factors of 2 and 5
+  while (tempDen % 2 === 0) tempDen /= 2;
+  while (tempDen % 5 === 0) tempDen /= 5;
+  const isTerminating = tempDen === 1;
+
+  steps.push({
+    label: isTerminating
+      ? `This is a terminating decimal`
+      : `This is a recurring decimal`,
+    math: `${toKatex(num, den)} = ${resultStr}${!isTerminating ? "..." : ""}`,
+    barFilled: num,
+    barTotal: den,
+    gridFilled: Math.min(100, Math.round(result * 100)),
+  });
+
+  return steps;
+}
+
+function DecimalGrid({ filled }: { filled: number }) {
+  return (
+    <div className="grid grid-cols-10 gap-0.5 rounded-lg border-2 border-border p-1" style={{ width: "fit-content" }}>
+      {Array.from({ length: 100 }, (_, i) => (
+        <div
+          key={i}
+          className="h-4 w-4 rounded-sm transition-colors duration-300"
+          style={{
+            backgroundColor: i < filled ? "var(--unit-3)" : "var(--background)",
+          }}
+        />
+      ))}
+    </div>
+  );
+}
+
+function FractionBarSmall({ filled, total }: { filled: number; total: number }) {
+  const segments = Math.min(total, 20);
+  const fillCount = Math.min(filled, segments);
+  return (
+    <div className="flex h-8 w-full max-w-[240px] overflow-hidden rounded-lg border-2 border-border">
+      {Array.from({ length: segments }, (_, i) => (
+        <div
+          key={i}
+          className="border-r border-border/30 transition-colors duration-300 last:border-r-0"
+          style={{
+            flex: 1,
+            backgroundColor: i < fillCount ? "var(--unit-3)" : "transparent",
+          }}
+        />
+      ))}
+    </div>
+  );
+}
+
+export function ConversionExplorer() {
+  const [mode, setMode] = useState<ConvertMode>("decToFrac");
+  const [decInput, setDecInput] = useState("0.75");
+  const [numInput, setNumInput] = useState("3");
+  const [denInput, setDenInput] = useState("8");
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function handleGo() {
+    setError("");
+    try {
+      let s: Step[];
+      if (mode === "decToFrac") {
+        const val = parseFloat(decInput);
+        if (isNaN(val) || val < 0 || val >= 10) {
+          setError("Enter a valid decimal between 0 and 10.");
+          return;
+        }
+        s = buildDecToFracSteps(decInput.trim());
+      } else {
+        const n = parseInt(numInput);
+        const d = parseInt(denInput);
+        if (isNaN(n) || isNaN(d) || d === 0) {
+          setError("Enter a valid fraction (denominator ≠ 0).");
+          return;
+        }
+        s = buildFracToDecSteps(n, d);
+      }
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not compute. Check your input.");
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }, [steps, currentStep]);
+
+  const stepBack = useCallback(() => {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }, [currentStep]);
+
+  const togglePlay = useCallback(() => setIsPlaying((p) => !p), []);
+
+  const reset = useCallback(() => {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }, []);
+
+  const step = steps ? steps[currentStep] : null;
+
+  return (
+    <div className="space-y-4">
+      {/* Mode tabs */}
+      <div className="flex gap-2">
+        <button
+          onClick={() => {
+            setMode("decToFrac");
+            reset();
+          }}
+          className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+            mode === "decToFrac"
+              ? "border-unit-3 bg-unit-3 text-white"
+              : "border-unit-3/40 text-unit-3 hover:bg-unit-3-light"
+          }`}
+        >
+          Decimal → Fraction
+        </button>
+        <button
+          onClick={() => {
+            setMode("fracToDec");
+            reset();
+          }}
+          className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+            mode === "fracToDec"
+              ? "border-unit-3 bg-unit-3 text-white"
+              : "border-unit-3/40 text-unit-3 hover:bg-unit-3-light"
+          }`}
+        >
+          Fraction → Decimal
+        </button>
+      </div>
+
+      {/* Input */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-3">
+          {mode === "decToFrac" ? "Enter a decimal" : "Enter a fraction"}
+        </p>
+        <div className="flex flex-wrap items-center gap-2.5">
+          {mode === "decToFrac" ? (
+            <input
+              type="text"
+              value={decInput}
+              onChange={(e) => setDecInput(e.target.value)}
+              onKeyDown={(e) => e.key === "Enter" && handleGo()}
+              placeholder="e.g. 0.75"
+              autoComplete="off"
+              className="max-w-[180px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-3"
+            />
+          ) : (
+            <div className="flex flex-col items-center">
+              <input
+                type="number"
+                value={numInput}
+                onChange={(e) => setNumInput(e.target.value)}
+                className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-3"
+                aria-label="Numerator"
+              />
+              <div className="my-0.5 h-0.5 w-12 bg-foreground" />
+              <input
+                type="number"
+                value={denInput}
+                onChange={(e) => setDenInput(e.target.value)}
+                className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-3"
+                aria-label="Denominator"
+              />
+            </div>
+          )}
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-3 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-3-dark"
+          >
+            Convert →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display */}
+      <Card className="flex min-h-[260px] flex-col items-center justify-center gap-4 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter a value above and click <strong>Convert</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            <MathDisplay math={step.math} className="text-2xl" />
+            <div className="flex flex-wrap items-center justify-center gap-6">
+              {step.gridFilled !== undefined && (
+                <div className="flex flex-col items-center gap-1">
+                  <DecimalGrid filled={step.gridFilled} />
+                  <span className="text-xs text-muted">{step.gridFilled}/100</span>
+                </div>
+              )}
+              {step.barFilled !== undefined && step.barTotal !== undefined && (
+                <div className="flex flex-col items-center gap-1">
+                  <FractionBarSmall filled={step.barFilled} total={step.barTotal} />
+                  <span className="text-xs text-muted">
+                    {step.barFilled}/{step.barTotal}
+                  </span>
+                </div>
+              )}
+            </div>
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !steps ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Answer</p>
+            <div className="text-3xl font-extrabold max-sm:text-2xl">
+              <MathDisplay math={steps[steps.length - 1].math} />
+            </div>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/decimal-arithmetic-explorer.tsx

@@ -0,0 +1,403 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+
+type DecOp = "add" | "subtract" | "multiply" | "divide";
+
+interface Step {
+  label: string;
+  columns: ColumnDisplay[];
+  carry?: string;
+  resultRow?: string;
+}
+
+interface ColumnDisplay {
+  rows: string[];
+  highlight?: number; // which row is highlighted
+  separator?: boolean; // line above this row
+}
+
+function padAndAlign(a: string, b: string): { aStr: string; bStr: string; dotPos: number } {
+  const aParts = a.split(".");
+  const bParts = b.split(".");
+  const aInt = aParts[0] || "0";
+  const bInt = bParts[0] || "0";
+  const aDec = aParts[1] || "";
+  const bDec = bParts[1] || "";
+
+  const maxInt = Math.max(aInt.length, bInt.length);
+  const maxDec = Math.max(aDec.length, bDec.length);
+
+  const aAligned = aInt.padStart(maxInt, " ") + (maxDec > 0 ? "." + aDec.padEnd(maxDec, "0") : "");
+  const bAligned = bInt.padStart(maxInt, " ") + (maxDec > 0 ? "." + bDec.padEnd(maxDec, "0") : "");
+
+  return { aStr: aAligned, bStr: bAligned, dotPos: maxInt };
+}
+
+function buildAddSubSteps(a: number, b: number, op: DecOp): Step[] {
+  const steps: Step[] = [];
+  const aStr = a.toString();
+  const bStr = b.toString();
+  const { aStr: aAligned, bStr: bAligned } = padAndAlign(aStr, bStr);
+
+  const opSymbol = op === "add" ? "+" : "−";
+  const result = op === "add" ? a + b : a - b;
+  const resultStr = parseFloat(result.toFixed(10)).toString();
+
+  // Step 0: Show the problem
+  steps.push({
+    label: `${aStr} ${opSymbol} ${bStr}`,
+    columns: [],
+  });
+
+  // Step 1: Align decimal points
+  steps.push({
+    label: "Align the decimal points",
+    columns: [
+      { rows: [aAligned, `${opSymbol} ${bAligned}`] },
+    ],
+  });
+
+  // Step 2: Add trailing zeros
+  steps.push({
+    label: "Fill in zeros as placeholders",
+    columns: [
+      { rows: [aAligned, `${opSymbol} ${bAligned}`], separator: true },
+    ],
+  });
+
+  // Step 3: Compute
+  const { aStr: aFinal, bStr: bFinal } = padAndAlign(aStr, bStr);
+  const resultAligned = padAndAlign(resultStr, aStr).aStr;
+
+  steps.push({
+    label: `Compute column by column`,
+    columns: [
+      { rows: [aFinal, `${opSymbol} ${bFinal}`, resultAligned], separator: true, highlight: 2 },
+    ],
+  });
+
+  // Step 4: Result
+  steps.push({
+    label: `${aStr} ${opSymbol} ${bStr} = ${resultStr}`,
+    columns: [
+      { rows: [aFinal, `${opSymbol} ${bFinal}`, resultAligned], separator: true, highlight: 2 },
+    ],
+    resultRow: resultStr,
+  });
+
+  return steps;
+}
+
+function buildMultiplySteps(a: number, b: number): Step[] {
+  const steps: Step[] = [];
+  const aStr = a.toString();
+  const bStr = b.toString();
+  const aDec = (aStr.split(".")[1] || "").length;
+  const bDec = (bStr.split(".")[1] || "").length;
+  const totalDec = aDec + bDec;
+
+  // Remove decimals for integer multiplication
+  const aInt = Math.round(a * Math.pow(10, aDec));
+  const bInt = Math.round(b * Math.pow(10, bDec));
+  const result = a * b;
+  const resultStr = parseFloat(result.toFixed(10)).toString();
+
+  steps.push({
+    label: `${aStr} × ${bStr}`,
+    columns: [],
+  });
+
+  if (totalDec > 0) {
+    steps.push({
+      label: `Count decimal places: ${aDec} + ${bDec} = ${totalDec}`,
+      columns: [
+        { rows: [`${aStr} → ${aDec} d.p.`, `${bStr} → ${bDec} d.p.`, `Total: ${totalDec} d.p.`] },
+      ],
+    });
+
+    steps.push({
+      label: `Multiply as whole numbers: ${aInt} × ${bInt}`,
+      columns: [
+        { rows: [`${aInt}`, `× ${bInt}`, `${aInt * bInt}`], separator: true, highlight: 2 },
+      ],
+    });
+
+    steps.push({
+      label: `Place decimal point ${totalDec} place${totalDec !== 1 ? "s" : ""} from the right`,
+      columns: [
+        { rows: [`${aInt * bInt}`, `→ ${resultStr}`], highlight: 1 },
+      ],
+      resultRow: resultStr,
+    });
+  } else {
+    const intResult = a * b;
+    steps.push({
+      label: `Multiply: ${aStr} × ${bStr} = ${intResult}`,
+      columns: [
+        { rows: [`${aStr}`, `× ${bStr}`, `${intResult}`], separator: true, highlight: 2 },
+      ],
+      resultRow: intResult.toString(),
+    });
+  }
+
+  return steps;
+}
+
+function buildDivideSteps(a: number, b: number): Step[] {
+  const steps: Step[] = [];
+  const aStr = a.toString();
+  const bStr = b.toString();
+  const result = a / b;
+  const resultStr = parseFloat(result.toFixed(10)).toString();
+
+  steps.push({
+    label: `${aStr} ÷ ${bStr}`,
+    columns: [],
+  });
+
+  // Make divisor a whole number
+  const bDec = (bStr.split(".")[1] || "").length;
+  if (bDec > 0) {
+    const factor = Math.pow(10, bDec);
+    const newA = parseFloat((a * factor).toFixed(10));
+    const newB = parseFloat((b * factor).toFixed(10));
+    steps.push({
+      label: `Make divisor whole: multiply both by ${factor}`,
+      columns: [
+        { rows: [`${aStr} × ${factor} = ${newA}`, `${bStr} × ${factor} = ${newB}`] },
+      ],
+    });
+    steps.push({
+      label: `Now divide: ${newA} ÷ ${newB}`,
+      columns: [
+        { rows: [`${newA} ÷ ${newB}`, `= ${resultStr}`], highlight: 1 },
+      ],
+    });
+  } else {
+    steps.push({
+      label: `Divide: ${aStr} ÷ ${bStr}`,
+      columns: [
+        { rows: [`${aStr} ÷ ${bStr}`, `= ${resultStr}`], highlight: 1 },
+      ],
+    });
+  }
+
+  steps.push({
+    label: `${aStr} ÷ ${bStr} = ${resultStr}`,
+    columns: [
+      { rows: [`${aStr} ÷ ${bStr} = ${resultStr}`] },
+    ],
+    resultRow: resultStr,
+  });
+
+  return steps;
+}
+
+function ColumnArithmetic({
+  columns,
+}: {
+  columns: ColumnDisplay[];
+}) {
+  if (columns.length === 0) return null;
+
+  return (
+    <div className="flex flex-col items-center gap-0.5 font-mono text-xl">
+      {columns.map((col, ci) =>
+        col.rows.map((row, ri) => (
+          <div key={`${ci}-${ri}`}>
+            {col.separator && ri === col.rows.length - 1 && (
+              <div className="mb-1 h-0.5 bg-foreground" />
+            )}
+            <div
+              className={`rounded-lg px-6 py-1.5 text-right tracking-wider transition-all duration-300 ${
+                ri === col.highlight
+                  ? "bg-unit-3-light font-bold text-foreground"
+                  : "text-foreground"
+              }`}
+            >
+              {row}
+            </div>
+          </div>
+        )),
+      )}
+    </div>
+  );
+}
+
+export function DecimalArithmeticExplorer() {
+  const [op, setOp] = useState<DecOp>("add");
+  const [aInput, setAInput] = useState("12.45");
+  const [bInput, setBInput] = useState("3.7");
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function handleGo() {
+    setError("");
+    const a = parseFloat(aInput);
+    const b = parseFloat(bInput);
+    if (isNaN(a) || isNaN(b)) {
+      setError("Enter valid decimal numbers.");
+      return;
+    }
+    if (op === "divide" && b === 0) {
+      setError("Cannot divide by zero.");
+      return;
+    }
+    try {
+      let s: Step[];
+      if (op === "add" || op === "subtract") {
+        s = buildAddSubSteps(a, b, op);
+      } else if (op === "multiply") {
+        s = buildMultiplySteps(a, b);
+      } else {
+        s = buildDivideSteps(a, b);
+      }
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not compute. Check your inputs.");
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }, [steps, currentStep]);
+
+  const stepBack = useCallback(() => {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }, [currentStep]);
+
+  const togglePlay = useCallback(() => setIsPlaying((p) => !p), []);
+
+  const reset = useCallback(() => {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }, []);
+
+  const step = steps ? steps[currentStep] : null;
+
+  const opLabels: Record<DecOp, string> = {
+    add: "Add (+)",
+    subtract: "Subtract (−)",
+    multiply: "Multiply (×)",
+    divide: "Divide (÷)",
+  };
+
+  return (
+    <div className="space-y-4">
+      {/* Operation tabs */}
+      <div className="flex flex-wrap gap-2">
+        {(["add", "subtract", "multiply", "divide"] as DecOp[]).map((o) => (
+          <button
+            key={o}
+            onClick={() => {
+              setOp(o);
+              reset();
+            }}
+            className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+              op === o
+                ? "border-unit-3 bg-unit-3 text-white"
+                : "border-unit-3/40 text-unit-3 hover:bg-unit-3-light"
+            }`}
+          >
+            {opLabels[o]}
+          </button>
+        ))}
+      </div>
+
+      {/* Input */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-3">
+          Enter two decimal numbers
+        </p>
+        <div className="flex flex-wrap items-center gap-2.5">
+          <input
+            type="text"
+            value={aInput}
+            onChange={(e) => setAInput(e.target.value)}
+            placeholder="e.g. 12.45"
+            autoComplete="off"
+            className="max-w-[140px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-3"
+            aria-label="First number"
+          />
+          <span className="text-xl font-bold text-muted">
+            {{ add: "+", subtract: "−", multiply: "×", divide: "÷" }[op]}
+          </span>
+          <input
+            type="text"
+            value={bInput}
+            onChange={(e) => setBInput(e.target.value)}
+            onKeyDown={(e) => e.key === "Enter" && handleGo()}
+            placeholder="e.g. 3.7"
+            autoComplete="off"
+            className="max-w-[140px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-3"
+            aria-label="Second number"
+          />
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-3 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-3-dark"
+          >
+            Go →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display */}
+      <Card className="flex min-h-[220px] flex-col items-center justify-center gap-4 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter numbers above and click <strong>Go</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            <ColumnArithmetic columns={step.columns} />
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !step?.resultRow ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Answer</p>
+            <p className="text-3xl font-extrabold text-foreground max-sm:text-2xl">
+              {step.resultRow}
+            </p>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/decimal-order-explorer.tsx

@@ -0,0 +1,311 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+
+type SortDirection = "ascending" | "descending";
+
+interface Step {
+  label: string;
+  values: { value: number; str: string; sorted: boolean; comparing: boolean }[];
+  comparingPair?: [number, number];
+}
+
+function padDecimal(s: string, maxInt: number, maxDec: number): string {
+  const parts = s.split(".");
+  const intPart = (parts[0] || "0").padStart(maxInt, "\u00A0"); // nbsp padding
+  const decPart = (parts[1] || "").padEnd(maxDec, "0");
+  return maxDec > 0 ? `${intPart}.${decPart}` : intPart;
+}
+
+function buildSortSteps(values: number[], direction: SortDirection): Step[] {
+  const steps: Step[] = [];
+  const strs = values.map((v) => v.toString());
+
+  // Find max integer and decimal lengths for alignment
+  const maxInt = Math.max(...strs.map((s) => s.split(".")[0].length));
+  const maxDec = Math.max(...strs.map((s) => (s.split(".")[1] || "").length));
+
+  // Step 0: Show unsorted
+  steps.push({
+    label: `Sort ${values.length} decimals in ${direction} order`,
+    values: values.map((v, i) => ({
+      value: v,
+      str: padDecimal(strs[i], maxInt, maxDec),
+      sorted: false,
+      comparing: false,
+    })),
+  });
+
+  // Step 1: Show aligned place values
+  steps.push({
+    label: "Align decimal points to compare place values",
+    values: values.map((v, i) => ({
+      value: v,
+      str: padDecimal(strs[i], maxInt, maxDec),
+      sorted: false,
+      comparing: false,
+    })),
+  });
+
+  // Bubble sort with steps
+  const arr = [...values];
+  const arrStrs = [...strs];
+  const cmp = direction === "ascending" ? (a: number, b: number) => a > b : (a: number, b: number) => a < b;
+
+  for (let i = 0; i < arr.length - 1; i++) {
+    for (let j = 0; j < arr.length - 1 - i; j++) {
+      // Show comparison
+      steps.push({
+        label: `Compare ${arrStrs[j]} and ${arrStrs[j + 1]}`,
+        values: arr.map((v, k) => ({
+          value: v,
+          str: padDecimal(arrStrs[k], maxInt, maxDec),
+          sorted: k >= arr.length - i,
+          comparing: k === j || k === j + 1,
+        })),
+        comparingPair: [j, j + 1],
+      });
+
+      if (cmp(arr[j], arr[j + 1])) {
+        // Swap
+        [arr[j], arr[j + 1]] = [arr[j + 1], arr[j]];
+        [arrStrs[j], arrStrs[j + 1]] = [arrStrs[j + 1], arrStrs[j]];
+
+        steps.push({
+          label: `Swap: ${arrStrs[j]} ${direction === "ascending" ? "<" : ">"} ${arrStrs[j + 1]}`,
+          values: arr.map((v, k) => ({
+            value: v,
+            str: padDecimal(arrStrs[k], maxInt, maxDec),
+            sorted: k >= arr.length - i,
+            comparing: k === j || k === j + 1,
+          })),
+        });
+      }
+    }
+  }
+
+  // Final step: Show sorted
+  steps.push({
+    label: `Sorted (${direction}): ${arrStrs.join(direction === "ascending" ? " < " : " > ")}`,
+    values: arr.map((v, k) => ({
+      value: v,
+      str: padDecimal(arrStrs[k], maxInt, maxDec),
+      sorted: true,
+      comparing: false,
+    })),
+  });
+
+  return steps;
+}
+
+function NumberLine({ values, min, max }: { values: { value: number; sorted: boolean; comparing: boolean }[]; min: number; max: number }) {
+  const range = max - min || 1;
+  return (
+    <div className="w-full max-w-lg">
+      <div className="relative h-2 rounded-full bg-border">
+        {values.map((v, i) => {
+          const pct = ((v.value - min) / range) * 100;
+          return (
+            <div
+              key={i}
+              className={`absolute -top-2.5 h-7 w-7 -translate-x-1/2 rounded-full border-2 text-center text-[0.6rem] font-bold leading-[1.5rem] transition-all duration-500 ${
+                v.comparing
+                  ? "border-hint bg-hint-light text-foreground z-10"
+                  : v.sorted
+                    ? "border-correct bg-correct-light text-foreground"
+                    : "border-unit-2 bg-unit-2-light text-foreground"
+              }`}
+              style={{ left: `${Math.max(5, Math.min(95, pct))}%` }}
+            >
+              {i + 1}
+            </div>
+          );
+        })}
+      </div>
+      <div className="mt-4 flex justify-between text-xs text-muted">
+        <span>{min}</span>
+        <span>{max}</span>
+      </div>
+    </div>
+  );
+}
+
+export function DecimalOrderExplorer() {
+  const [input, setInput] = useState("3.14, 3.1, 3.141, 3.04, 3.4");
+  const [direction, setDirection] = useState<SortDirection>("ascending");
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function handleGo() {
+    setError("");
+    const parts = input
+      .split(/[,\s]+/)
+      .map((s) => s.trim())
+      .filter(Boolean);
+    if (parts.length < 2) {
+      setError("Enter at least 2 decimals separated by commas.");
+      return;
+    }
+    if (parts.length > 6) {
+      setError("Maximum 6 decimals.");
+      return;
+    }
+    const values = parts.map(Number);
+    if (values.some(isNaN)) {
+      setError("All values must be valid numbers.");
+      return;
+    }
+    try {
+      const s = buildSortSteps(values, direction);
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not process. Check your input.");
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }, [steps, currentStep]);
+
+  const stepBack = useCallback(() => {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }, [currentStep]);
+
+  const togglePlay = useCallback(() => setIsPlaying((p) => !p), []);
+
+  const reset = useCallback(() => {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }, []);
+
+  const step = steps ? steps[currentStep] : null;
+
+  return (
+    <div className="space-y-4">
+      {/* Direction tabs */}
+      <div className="flex gap-2">
+        {(["ascending", "descending"] as SortDirection[]).map((d) => (
+          <button
+            key={d}
+            onClick={() => {
+              setDirection(d);
+              reset();
+            }}
+            className={`rounded-full border-2 px-4 py-2 text-sm font-semibold capitalize transition-colors ${
+              direction === d
+                ? "border-unit-2 bg-unit-2 text-white"
+                : "border-unit-2/40 text-unit-2 hover:bg-unit-2-light"
+            }`}
+          >
+            {d}
+          </button>
+        ))}
+      </div>
+
+      {/* Input */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-2">
+          Enter 2-6 decimal numbers (comma separated)
+        </p>
+        <div className="flex flex-wrap items-center gap-2.5">
+          <input
+            type="text"
+            value={input}
+            onChange={(e) => setInput(e.target.value)}
+            onKeyDown={(e) => e.key === "Enter" && handleGo()}
+            placeholder="e.g. 3.14, 3.1, 3.141"
+            autoComplete="off"
+            className="max-w-[320px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-2"
+          />
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-2 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-2-dark"
+          >
+            Sort →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display */}
+      <Card className="flex min-h-[280px] flex-col items-center justify-center gap-5 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter decimals above and click <strong>Sort</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            {/* Place value columns */}
+            <div className="flex flex-col gap-1.5 font-mono text-xl">
+              {step.values.map((v, i) => (
+                <div
+                  key={i}
+                  className={`rounded-lg border-2 px-4 py-2 text-center transition-all duration-300 ${
+                    v.comparing
+                      ? "border-hint bg-hint-light"
+                      : v.sorted
+                        ? "border-correct bg-correct-light"
+                        : "border-border bg-surface"
+                  }`}
+                >
+                  {v.str}
+                </div>
+              ))}
+            </div>
+            {/* Number line */}
+            <NumberLine
+              values={step.values}
+              min={Math.min(...step.values.map((v) => v.value)) - 0.1}
+              max={Math.max(...step.values.map((v) => v.value)) + 0.1}
+            />
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !steps ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">
+              Sorted ({direction})
+            </p>
+            <p className="text-2xl font-extrabold text-foreground max-sm:text-xl">
+              {step!.values.map((v) => v.value).join(direction === "ascending" ? " < " : " > ")}
+            </p>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/fraction-operation-explorer.tsx

@@ -0,0 +1,389 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+import { gcd, lcm, simplify, toKatex } from "@/lib/math/fractions";
+import { MathDisplay } from "@/components/math/math-display";
+
+type Operation = "add" | "subtract" | "multiply" | "divide";
+
+interface Step {
+  label: string;
+  math: string;
+  barA: { filled: number; total: number };
+  barB: { filled: number; total: number };
+  barResult?: { filled: number; total: number };
+}
+
+function buildSteps(
+  n1: number, d1: number,
+  n2: number, d2: number,
+  op: Operation,
+): Step[] {
+  const steps: Step[] = [];
+
+  // Step 0: Show the original fractions
+  const opSymbol = { add: "+", subtract: "-", multiply: "\\times", divide: "\\div" }[op];
+  steps.push({
+    label: "Start with the two fractions",
+    math: `${toKatex(n1, d1)} ${opSymbol} ${toKatex(n2, d2)}`,
+    barA: { filled: n1, total: d1 },
+    barB: { filled: n2, total: d2 },
+  });
+
+  if (op === "add" || op === "subtract") {
+    // Step 1: Find LCD
+    const lcd = lcm(d1, d2);
+    const mult1 = lcd / d1;
+    const mult2 = lcd / d2;
+    const cn1 = n1 * mult1;
+    const cn2 = n2 * mult2;
+
+    if (d1 !== d2) {
+      steps.push({
+        label: `Find the LCD of ${d1} and ${d2}`,
+        math: `\\text{LCD}(${d1}, ${d2}) = ${lcd}`,
+        barA: { filled: n1, total: d1 },
+        barB: { filled: n2, total: d2 },
+      });
+
+      // Step 2: Convert both fractions
+      steps.push({
+        label: "Convert to equivalent fractions with the LCD",
+        math: `${toKatex(n1, d1)} = ${toKatex(cn1, lcd)} \\quad ${toKatex(n2, d2)} = ${toKatex(cn2, lcd)}`,
+        barA: { filled: cn1, total: lcd },
+        barB: { filled: cn2, total: lcd },
+      });
+    }
+
+    // Step 3: Perform the operation
+    const resultNum = op === "add" ? cn1 + cn2 : cn1 - cn2;
+    steps.push({
+      label: op === "add" ? "Add the numerators" : "Subtract the numerators",
+      math: `${toKatex(cn1, lcd)} ${opSymbol} ${toKatex(cn2, lcd)} = ${toKatex(resultNum, lcd)}`,
+      barA: { filled: cn1, total: lcd },
+      barB: { filled: cn2, total: lcd },
+      barResult: { filled: Math.abs(resultNum), total: lcd },
+    });
+
+    // Step 4: Simplify if needed
+    const [sn, sd] = simplify(resultNum, lcd);
+    if (Math.abs(sn) !== Math.abs(resultNum) || sd !== lcd) {
+      const g = gcd(Math.abs(resultNum), lcd);
+      steps.push({
+        label: `Simplify by dividing by GCD = ${g}`,
+        math: `${toKatex(resultNum, lcd)} = ${toKatex(sn, sd)}`,
+        barA: { filled: cn1, total: lcd },
+        barB: { filled: cn2, total: lcd },
+        barResult: { filled: Math.abs(sn), total: sd },
+      });
+    }
+  } else if (op === "multiply") {
+    // Step 1: Multiply numerators and denominators
+    const rn = n1 * n2;
+    const rd = d1 * d2;
+    steps.push({
+      label: "Multiply numerators and denominators",
+      math: `\\frac{${n1} \\times ${n2}}{${d1} \\times ${d2}} = ${toKatex(rn, rd)}`,
+      barA: { filled: n1, total: d1 },
+      barB: { filled: n2, total: d2 },
+      barResult: { filled: rn, total: rd },
+    });
+
+    // Step 2: Simplify
+    const [sn, sd] = simplify(rn, rd);
+    if (sn !== rn || sd !== rd) {
+      const g = gcd(Math.abs(rn), rd);
+      steps.push({
+        label: `Simplify by dividing by GCD = ${g}`,
+        math: `${toKatex(rn, rd)} = ${toKatex(sn, sd)}`,
+        barA: { filled: n1, total: d1 },
+        barB: { filled: n2, total: d2 },
+        barResult: { filled: Math.abs(sn), total: sd },
+      });
+    }
+  } else {
+    // divide: invert and multiply
+    steps.push({
+      label: "Invert the second fraction (reciprocal)",
+      math: `${toKatex(n1, d1)} \\times ${toKatex(d2, n2)}`,
+      barA: { filled: n1, total: d1 },
+      barB: { filled: d2, total: n2 },
+    });
+
+    const rn = n1 * d2;
+    const rd = d1 * n2;
+    steps.push({
+      label: "Multiply numerators and denominators",
+      math: `\\frac{${n1} \\times ${d2}}{${d1} \\times ${n2}} = ${toKatex(rn, rd)}`,
+      barA: { filled: n1, total: d1 },
+      barB: { filled: d2, total: n2 },
+      barResult: { filled: rn, total: rd },
+    });
+
+    const [sn, sd] = simplify(rn, rd);
+    if (sn !== rn || sd !== rd) {
+      const g = gcd(Math.abs(rn), rd);
+      steps.push({
+        label: `Simplify by dividing by GCD = ${g}`,
+        math: `${toKatex(rn, rd)} = ${toKatex(sn, sd)}`,
+        barA: { filled: n1, total: d1 },
+        barB: { filled: d2, total: n2 },
+        barResult: { filled: Math.abs(sn), total: sd },
+      });
+    }
+  }
+
+  return steps;
+}
+
+function FractionBar({
+  filled,
+  total,
+  color,
+  label,
+}: {
+  filled: number;
+  total: number;
+  color: string;
+  label?: string;
+}) {
+  const maxSegments = Math.min(total, 24);
+  const fillCount = Math.min(filled, maxSegments);
+
+  return (
+    <div className="flex flex-col items-center gap-1">
+      {label && <span className="text-xs font-medium text-muted">{label}</span>}
+      <div className="flex h-10 w-full max-w-[280px] overflow-hidden rounded-lg border-2 border-border">
+        {Array.from({ length: maxSegments }, (_, i) => (
+          <div
+            key={i}
+            className="border-r border-border/30 transition-colors duration-500 last:border-r-0"
+            style={{
+              flex: 1,
+              backgroundColor: i < fillCount ? color : "transparent",
+            }}
+          />
+        ))}
+      </div>
+      <span className="text-xs text-muted">
+        {filled}/{total}
+      </span>
+    </div>
+  );
+}
+
+export function FractionOperationExplorer() {
+  const [op, setOp] = useState<Operation>("add");
+  const [n1, setN1] = useState("1");
+  const [d1, setD1] = useState("3");
+  const [n2, setN2] = useState("1");
+  const [d2, setD2] = useState("4");
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function handleGo() {
+    setError("");
+    const nums = [parseInt(n1), parseInt(d1), parseInt(n2), parseInt(d2)];
+    if (nums.some(isNaN) || nums.some((n) => n === 0)) {
+      setError("Enter valid non-zero numbers.");
+      return;
+    }
+    if (nums[1] < 0 || nums[3] < 0) {
+      setError("Denominators must be positive.");
+      return;
+    }
+    if (nums.some((n) => Math.abs(n) > 99)) {
+      setError("Keep numbers under 100.");
+      return;
+    }
+    try {
+      const s = buildSteps(nums[0], nums[1], nums[2], nums[3], op);
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not compute. Check your inputs.");
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }, [steps, currentStep]);
+
+  const stepBack = useCallback(() => {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }, [currentStep]);
+
+  const togglePlay = useCallback(() => setIsPlaying((p) => !p), []);
+
+  const reset = useCallback(() => {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }, []);
+
+  const step = steps ? steps[currentStep] : null;
+
+  const opLabels: Record<Operation, string> = {
+    add: "Add (+)",
+    subtract: "Subtract (−)",
+    multiply: "Multiply (×)",
+    divide: "Divide (÷)",
+  };
+
+  return (
+    <div className="space-y-4">
+      {/* Operation tabs */}
+      <div className="flex flex-wrap gap-2">
+        {(["add", "subtract", "multiply", "divide"] as Operation[]).map((o) => (
+          <button
+            key={o}
+            onClick={() => {
+              setOp(o);
+              reset();
+            }}
+            className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+              op === o
+                ? "border-unit-1 bg-unit-1 text-white"
+                : "border-unit-1/40 text-unit-1 hover:bg-unit-1-light"
+            }`}
+          >
+            {opLabels[o]}
+          </button>
+        ))}
+      </div>
+
+      {/* Input Card */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-1">
+          Enter two fractions
+        </p>
+        <div className="flex flex-wrap items-center gap-3">
+          <div className="flex items-center gap-1">
+            <div className="flex flex-col items-center">
+              <input
+                type="number"
+                value={n1}
+                onChange={(e) => setN1(e.target.value)}
+                className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-1"
+                aria-label="Numerator 1"
+              />
+              <div className="my-0.5 h-0.5 w-12 bg-foreground" />
+              <input
+                type="number"
+                value={d1}
+                onChange={(e) => setD1(e.target.value)}
+                className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-1"
+                aria-label="Denominator 1"
+              />
+            </div>
+          </div>
+          <span className="text-xl font-bold text-muted">
+            {{ add: "+", subtract: "−", multiply: "×", divide: "÷" }[op]}
+          </span>
+          <div className="flex items-center gap-1">
+            <div className="flex flex-col items-center">
+              <input
+                type="number"
+                value={n2}
+                onChange={(e) => setN2(e.target.value)}
+                className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-1"
+                aria-label="Numerator 2"
+              />
+              <div className="my-0.5 h-0.5 w-12 bg-foreground" />
+              <input
+                type="number"
+                value={d2}
+                onChange={(e) => setD2(e.target.value)}
+                className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-1"
+                aria-label="Denominator 2"
+              />
+            </div>
+          </div>
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-1 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-1-dark"
+          >
+            Go →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display Card */}
+      <Card className="flex min-h-[240px] flex-col items-center justify-center gap-5 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter fractions above and click <strong>Go</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            <MathDisplay math={step.math} className="text-2xl" />
+            <div className="flex w-full max-w-md flex-col gap-3">
+              <FractionBar
+                filled={step.barA.filled}
+                total={step.barA.total}
+                color="var(--unit-1)"
+                label="First"
+              />
+              <FractionBar
+                filled={step.barB.filled}
+                total={step.barB.total}
+                color="var(--unit-1-dark)"
+                label="Second"
+              />
+              {step.barResult && (
+                <FractionBar
+                  filled={step.barResult.filled}
+                  total={step.barResult.total}
+                  color="var(--correct)"
+                  label="Result"
+                />
+              )}
+            </div>
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !steps ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Answer</p>
+            <div className="text-3xl font-extrabold max-sm:text-2xl">
+              <MathDisplay math={steps[steps.length - 1].math} />
+            </div>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/fraction-quantity-explorer.tsx

@@ -0,0 +1,305 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+import { MathDisplay } from "@/components/math/math-display";
+import { toKatex } from "@/lib/math/fractions";
+
+type FQMode = "fractionOf" | "findWhole";
+
+interface Step {
+  label: string;
+  math: string;
+  barFilled: number; // 0–1 proportion
+  barLabel?: string;
+}
+
+function buildFractionOfSteps(num: number, den: number, quantity: number): Step[] {
+  const steps: Step[] = [];
+
+  steps.push({
+    label: `Find ${toKatexStr(num, den)} of ${quantity}`,
+    math: `${toKatex(num, den)} \\text{ of } ${quantity}`,
+    barFilled: 0,
+  });
+
+  // Step 1: Divide quantity by denominator
+  const onePart = quantity / den;
+  steps.push({
+    label: `Divide ${quantity} by ${den} to find one part`,
+    math: `${quantity} \\div ${den} = ${fmt(onePart)}`,
+    barFilled: 1 / den,
+    barLabel: fmt(onePart),
+  });
+
+  // Step 2: Multiply by numerator
+  const result = onePart * num;
+  steps.push({
+    label: `Multiply one part by ${num}`,
+    math: `${fmt(onePart)} \\times ${num} = ${fmt(result)}`,
+    barFilled: num / den,
+    barLabel: fmt(result),
+  });
+
+  steps.push({
+    label: `Answer: ${toKatexStr(num, den)} of ${quantity} = ${fmt(result)}`,
+    math: `${toKatex(num, den)} \\times ${quantity} = ${fmt(result)}`,
+    barFilled: num / den,
+    barLabel: fmt(result),
+  });
+
+  return steps;
+}
+
+function buildFindWholeSteps(num: number, den: number, part: number): Step[] {
+  const steps: Step[] = [];
+
+  steps.push({
+    label: `If ${toKatexStr(num, den)} of the whole = ${part}, find the whole`,
+    math: `${toKatex(num, den)} \\text{ of ? } = ${part}`,
+    barFilled: num / den,
+    barLabel: `${part}`,
+  });
+
+  // Step 1: Find one part
+  const onePart = part / num;
+  steps.push({
+    label: `Divide ${part} by ${num} to find one ${den}th`,
+    math: `${part} \\div ${num} = ${fmt(onePart)}`,
+    barFilled: 1 / den,
+    barLabel: fmt(onePart),
+  });
+
+  // Step 2: Multiply by denominator
+  const whole = onePart * den;
+  steps.push({
+    label: `Multiply by ${den} to find the whole`,
+    math: `${fmt(onePart)} \\times ${den} = ${fmt(whole)}`,
+    barFilled: 1,
+    barLabel: fmt(whole),
+  });
+
+  steps.push({
+    label: `The whole is ${fmt(whole)}`,
+    math: `\\text{Whole} = ${fmt(whole)}`,
+    barFilled: 1,
+    barLabel: fmt(whole),
+  });
+
+  return steps;
+}
+
+function toKatexStr(n: number, d: number): string {
+  return `${n}/${d}`;
+}
+
+function fmt(n: number): string {
+  return Number.isInteger(n) ? n.toString() : n.toFixed(2);
+}
+
+function QuantityBar({ filled, label }: { filled: number; label?: string }) {
+  const pct = Math.max(0, Math.min(1, filled)) * 100;
+  return (
+    <div className="w-full max-w-md">
+      <div className="relative h-12 overflow-hidden rounded-xl border-2 border-border bg-background">
+        <div
+          className="flex h-full items-center justify-center bg-unit-1 text-sm font-bold text-white transition-all duration-700"
+          style={{ width: `${pct}%` }}
+        >
+          {label && pct > 15 ? label : ""}
+        </div>
+      </div>
+      {label && pct <= 15 && (
+        <p className="mt-1 text-center text-sm font-semibold text-unit-1">{label}</p>
+      )}
+      <div className="mt-1 flex justify-between text-xs text-muted">
+        <span>0</span>
+        <span>{Math.round(pct)}%</span>
+      </div>
+    </div>
+  );
+}
+
+export function FractionQuantityExplorer() {
+  const [mode, setMode] = useState<FQMode>("fractionOf");
+  const [num, setNum] = useState("3");
+  const [den, setDen] = useState("4");
+  const [quantity, setQuantity] = useState("80");
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function handleGo() {
+    setError("");
+    const n = parseInt(num);
+    const d = parseInt(den);
+    const q = parseFloat(quantity);
+    if (isNaN(n) || isNaN(d) || d === 0) {
+      setError("Enter a valid fraction (denominator ≠ 0).");
+      return;
+    }
+    if (isNaN(q) || q <= 0) {
+      setError("Enter a valid positive quantity.");
+      return;
+    }
+    try {
+      const s =
+        mode === "fractionOf"
+          ? buildFractionOfSteps(n, d, q)
+          : buildFindWholeSteps(n, d, q);
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not compute. Check your inputs.");
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }, [steps, currentStep]);
+
+  const stepBack = useCallback(() => {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }, [currentStep]);
+
+  const togglePlay = useCallback(() => setIsPlaying((p) => !p), []);
+
+  const reset = useCallback(() => {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }, []);
+
+  const step = steps ? steps[currentStep] : null;
+
+  return (
+    <div className="space-y-4">
+      {/* Mode tabs */}
+      <div className="flex flex-wrap gap-2">
+        <button
+          onClick={() => {
+            setMode("fractionOf");
+            reset();
+          }}
+          className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+            mode === "fractionOf"
+              ? "border-unit-1 bg-unit-1 text-white"
+              : "border-unit-1/40 text-unit-1 hover:bg-unit-1-light"
+          }`}
+        >
+          Fraction OF Quantity
+        </button>
+        <button
+          onClick={() => {
+            setMode("findWhole");
+            reset();
+          }}
+          className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+            mode === "findWhole"
+              ? "border-unit-1 bg-unit-1 text-white"
+              : "border-unit-1/40 text-unit-1 hover:bg-unit-1-light"
+          }`}
+        >
+          Find the WHOLE
+        </button>
+      </div>
+
+      {/* Input */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-1">
+          {mode === "fractionOf" ? "Enter a fraction and quantity" : "Enter a fraction and the part value"}
+        </p>
+        <div className="flex flex-wrap items-center gap-3">
+          <div className="flex flex-col items-center">
+            <input
+              type="number"
+              value={num}
+              onChange={(e) => setNum(e.target.value)}
+              className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-1"
+              aria-label="Numerator"
+            />
+            <div className="my-0.5 h-0.5 w-12 bg-foreground" />
+            <input
+              type="number"
+              value={den}
+              onChange={(e) => setDen(e.target.value)}
+              className="w-14 rounded-lg border-2 border-border bg-surface px-2 py-1.5 text-center text-lg font-bold outline-none focus:border-unit-1"
+              aria-label="Denominator"
+            />
+          </div>
+          <span className="text-lg font-semibold text-muted">
+            {mode === "fractionOf" ? "of" : "= "}
+          </span>
+          <input
+            type="number"
+            value={quantity}
+            onChange={(e) => setQuantity(e.target.value)}
+            onKeyDown={(e) => e.key === "Enter" && handleGo()}
+            className="w-24 rounded-lg border-2 border-border bg-surface px-3 py-2.5 text-center text-lg font-bold outline-none focus:border-unit-1"
+            aria-label={mode === "fractionOf" ? "Quantity" : "Part value"}
+          />
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-1 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-1-dark"
+          >
+            Go →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display */}
+      <Card className="flex min-h-[220px] flex-col items-center justify-center gap-4 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter values above and click <strong>Go</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            <MathDisplay math={step.math} className="text-2xl" />
+            <QuantityBar filled={step.barFilled} label={step.barLabel} />
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !steps ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Answer</p>
+            <div className="text-3xl font-extrabold max-sm:text-2xl">
+              <MathDisplay math={steps[steps.length - 1].math} />
+            </div>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/ratio-explorer.tsx

@@ -0,0 +1,401 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+import { MathDisplay } from "@/components/math/math-display";
+import { simplifyRatio } from "@/lib/math/ratios";
+import { gcd } from "@/lib/math/fractions";
+
+type RatioMode = "divide" | "simplify" | "equivalent";
+
+interface Step {
+  label: string;
+  math: string;
+  barSegments: { value: number; filled: boolean; label?: string }[];
+}
+
+const COLORS = ["var(--unit-4)", "var(--unit-1)", "var(--unit-3)", "var(--hint)"];
+
+function buildDivideSteps(total: number, parts: number[]): Step[] {
+  const steps: Step[] = [];
+  const sum = parts.reduce((a, b) => a + b, 0);
+
+  // Step 0: Show the ratio and total
+  steps.push({
+    label: `Divide ${total} in the ratio ${parts.join(" : ")}`,
+    math: `${total} \\div (${parts.join(" : ")})`,
+    barSegments: parts.map((p) => ({ value: p, filled: false })),
+  });
+
+  // Step 1: Sum the parts
+  steps.push({
+    label: `Add the ratio parts: ${parts.join(" + ")} = ${sum}`,
+    math: `${parts.join(" + ")} = ${sum} \\text{ total parts}`,
+    barSegments: parts.map((p) => ({ value: p, filled: false })),
+  });
+
+  // Step 2: Find one part
+  const onePart = total / sum;
+  steps.push({
+    label: `Find one part: ${total} ÷ ${sum} = ${onePart}`,
+    math: `\\text{One part} = ${total} \\div ${sum} = ${Number.isInteger(onePart) ? onePart : onePart.toFixed(2)}`,
+    barSegments: parts.map((p) => ({ value: p, filled: false })),
+  });
+
+  // Steps 3+: Calculate each share
+  const shares: number[] = [];
+  parts.forEach((p, i) => {
+    const share = p * onePart;
+    shares.push(share);
+    steps.push({
+      label: `Part ${i + 1}: ${p} × ${Number.isInteger(onePart) ? onePart : onePart.toFixed(2)} = ${Number.isInteger(share) ? share : share.toFixed(2)}`,
+      math: `${p} \\times ${Number.isInteger(onePart) ? onePart : onePart.toFixed(2)} = ${Number.isInteger(share) ? share : share.toFixed(2)}`,
+      barSegments: parts.map((pp, j) => ({
+        value: pp,
+        filled: j <= i,
+        label: j <= i ? `${Number.isInteger(shares[j]) ? shares[j] : shares[j].toFixed(2)}` : undefined,
+      })),
+    });
+  });
+
+  // Final step: Show all shares
+  const shareStrs = shares.map((s) => (Number.isInteger(s) ? s.toString() : s.toFixed(2)));
+  steps.push({
+    label: `Result: ${shareStrs.join(", ")}`,
+    math: `${total} = ${shareStrs.join(" + ")}`,
+    barSegments: parts.map((pp, j) => ({
+      value: pp,
+      filled: true,
+      label: shareStrs[j],
+    })),
+  });
+
+  return steps;
+}
+
+function buildSimplifySteps(parts: number[]): Step[] {
+  const steps: Step[] = [];
+
+  steps.push({
+    label: `Simplify the ratio ${parts.join(" : ")}`,
+    math: parts.join(" : "),
+    barSegments: parts.map((p) => ({ value: p, filled: true })),
+  });
+
+  // Find GCD
+  let g = parts[0];
+  for (let i = 1; i < parts.length; i++) g = gcd(g, parts[i]);
+
+  if (g === 1) {
+    steps.push({
+      label: "The ratio is already in its simplest form (GCD = 1)",
+      math: `\\text{GCD} = 1`,
+      barSegments: parts.map((p) => ({ value: p, filled: true })),
+    });
+  } else {
+    steps.push({
+      label: `Find the GCD of all parts: ${g}`,
+      math: `\\text{GCD}(${parts.join(", ")}) = ${g}`,
+      barSegments: parts.map((p) => ({ value: p, filled: true })),
+    });
+
+    const simplified = simplifyRatio(parts);
+    steps.push({
+      label: `Divide each part by ${g}`,
+      math: parts.map((p) => `${p} \\div ${g} = ${p / g}`).join(", \\quad "),
+      barSegments: simplified.map((p) => ({ value: p, filled: true })),
+    });
+
+    steps.push({
+      label: `Simplified ratio: ${simplified.join(" : ")}`,
+      math: `${parts.join(" : ")} = ${simplified.join(" : ")}`,
+      barSegments: simplified.map((p) => ({ value: p, filled: true })),
+    });
+  }
+
+  return steps;
+}
+
+function buildEquivalentSteps(parts: number[], multiplier: number): Step[] {
+  const steps: Step[] = [];
+
+  steps.push({
+    label: `Find an equivalent ratio: ${parts.join(" : ")} × ${multiplier}`,
+    math: `(${parts.join(" : ")}) \\times ${multiplier}`,
+    barSegments: parts.map((p) => ({ value: p, filled: true })),
+  });
+
+  const result = parts.map((p) => p * multiplier);
+  steps.push({
+    label: `Multiply each part by ${multiplier}`,
+    math: parts.map((p) => `${p} \\times ${multiplier} = ${p * multiplier}`).join(", \\quad "),
+    barSegments: result.map((p) => ({ value: p, filled: true })),
+  });
+
+  steps.push({
+    label: `Equivalent ratio: ${result.join(" : ")}`,
+    math: `${parts.join(" : ")} = ${result.join(" : ")}`,
+    barSegments: result.map((p) => ({ value: p, filled: true })),
+  });
+
+  return steps;
+}
+
+function RatioBar({
+  segments,
+}: {
+  segments: { value: number; filled: boolean; label?: string }[];
+}) {
+  const total = segments.reduce((s, seg) => s + seg.value, 0);
+  if (total === 0) return null;
+
+  return (
+    <div className="w-full max-w-lg">
+      <div className="flex h-14 overflow-hidden rounded-xl border-2 border-border">
+        {segments.map((seg, i) => (
+          <div
+            key={i}
+            className="relative flex items-center justify-center border-r border-white/40 text-sm font-bold text-white transition-all duration-500 last:border-r-0"
+            style={{
+              flex: seg.value,
+              backgroundColor: seg.filled ? COLORS[i % COLORS.length] : "transparent",
+              color: seg.filled ? "white" : "var(--foreground)",
+            }}
+          >
+            {seg.label || seg.value}
+          </div>
+        ))}
+      </div>
+      <div className="mt-1 flex">
+        {segments.map((seg, i) => (
+          <div
+            key={i}
+            className="text-center text-xs text-muted"
+            style={{ flex: seg.value }}
+          >
+            {seg.label && `(${seg.value} parts)`}
+          </div>
+        ))}
+      </div>
+    </div>
+  );
+}
+
+export function RatioExplorer() {
+  const [mode, setMode] = useState<RatioMode>("divide");
+  const [partA, setPartA] = useState("2");
+  const [partB, setPartB] = useState("3");
+  const [partC, setPartC] = useState("");
+  const [total, setTotal] = useState("60");
+  const [multiplier, setMultiplier] = useState("4");
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function getParts(): number[] {
+    const parts = [parseInt(partA), parseInt(partB)];
+    if (partC.trim()) parts.push(parseInt(partC));
+    return parts;
+  }
+
+  function handleGo() {
+    setError("");
+    const parts = getParts();
+    if (parts.some(isNaN) || parts.some((p) => p <= 0)) {
+      setError("Enter valid positive ratio parts.");
+      return;
+    }
+
+    try {
+      let s: Step[];
+      if (mode === "divide") {
+        const t = parseFloat(total);
+        if (isNaN(t) || t <= 0) {
+          setError("Enter a valid positive total.");
+          return;
+        }
+        s = buildDivideSteps(t, parts);
+      } else if (mode === "simplify") {
+        s = buildSimplifySteps(parts);
+      } else {
+        const m = parseInt(multiplier);
+        if (isNaN(m) || m <= 0) {
+          setError("Enter a valid positive multiplier.");
+          return;
+        }
+        s = buildEquivalentSteps(parts, m);
+      }
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not compute. Check your inputs.");
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }, [steps, currentStep]);
+
+  const stepBack = useCallback(() => {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }, [currentStep]);
+
+  const togglePlay = useCallback(() => setIsPlaying((p) => !p), []);
+
+  const reset = useCallback(() => {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }, []);
+
+  const step = steps ? steps[currentStep] : null;
+
+  const modeLabels: Record<RatioMode, string> = {
+    divide: "Divide in Ratio",
+    simplify: "Simplify Ratio",
+    equivalent: "Equivalent Ratio",
+  };
+
+  return (
+    <div className="space-y-4">
+      {/* Mode tabs */}
+      <div className="flex flex-wrap gap-2">
+        {(["divide", "simplify", "equivalent"] as RatioMode[]).map((m) => (
+          <button
+            key={m}
+            onClick={() => {
+              setMode(m);
+              reset();
+            }}
+            className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+              mode === m
+                ? "border-unit-4 bg-unit-4 text-white"
+                : "border-unit-4/40 text-unit-4 hover:bg-unit-4-light"
+            }`}
+          >
+            {modeLabels[m]}
+          </button>
+        ))}
+      </div>
+
+      {/* Input */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-4">
+          {mode === "divide" ? "Enter ratio parts and total" : mode === "simplify" ? "Enter ratio parts" : "Enter ratio parts and multiplier"}
+        </p>
+        <div className="flex flex-wrap items-center gap-2.5">
+          <input
+            type="number"
+            value={partA}
+            onChange={(e) => setPartA(e.target.value)}
+            className="w-16 rounded-lg border-2 border-border bg-surface px-2 py-2.5 text-center text-lg font-bold outline-none focus:border-unit-4"
+            aria-label="Part A"
+          />
+          <span className="text-xl font-bold text-muted">:</span>
+          <input
+            type="number"
+            value={partB}
+            onChange={(e) => setPartB(e.target.value)}
+            className="w-16 rounded-lg border-2 border-border bg-surface px-2 py-2.5 text-center text-lg font-bold outline-none focus:border-unit-4"
+            aria-label="Part B"
+          />
+          <span className="text-xl font-bold text-muted">:</span>
+          <input
+            type="number"
+            value={partC}
+            onChange={(e) => setPartC(e.target.value)}
+            placeholder="?"
+            className="w-16 rounded-lg border-2 border-border bg-surface px-2 py-2.5 text-center text-lg font-bold outline-none focus:border-unit-4"
+            aria-label="Part C (optional)"
+          />
+
+          {mode === "divide" && (
+            <>
+              <span className="text-sm font-medium text-muted">Total:</span>
+              <input
+                type="number"
+                value={total}
+                onChange={(e) => setTotal(e.target.value)}
+                className="w-20 rounded-lg border-2 border-border bg-surface px-2 py-2.5 text-center text-lg font-bold outline-none focus:border-unit-4"
+                aria-label="Total"
+              />
+            </>
+          )}
+          {mode === "equivalent" && (
+            <>
+              <span className="text-sm font-medium text-muted">× </span>
+              <input
+                type="number"
+                value={multiplier}
+                onChange={(e) => setMultiplier(e.target.value)}
+                className="w-16 rounded-lg border-2 border-border bg-surface px-2 py-2.5 text-center text-lg font-bold outline-none focus:border-unit-4"
+                aria-label="Multiplier"
+              />
+            </>
+          )}
+
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-4 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-4-dark"
+          >
+            Go →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display */}
+      <Card className="flex min-h-[220px] flex-col items-center justify-center gap-4 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter values above and click <strong>Go</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            <MathDisplay math={step.math} className="text-xl" />
+            <RatioBar segments={step.barSegments} />
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !steps ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Answer</p>
+            <p className="text-2xl font-extrabold text-foreground max-sm:text-xl">
+              {steps[steps.length - 1].label.replace("Result: ", "").replace("Simplified ratio: ", "").replace("Equivalent ratio: ", "")}
+            </p>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/rounding-explorer.tsx

@@ -0,0 +1,559 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+
+type RoundTarget = "whole" | "1dp" | "2dp" | "1sf" | "2sf" | "3sf";
+
+interface Step {
+  label: string;
+  digits: DigitInfo[];
+  resultText?: string;
+}
+
+interface DigitInfo {
+  char: string;
+  state: "normal" | "target" | "decider" | "dim" | "significant";
+}
+
+function getDigits(value: string): string[] {
+  return value.split("");
+}
+
+// ── Decimal place rounding steps ─────────────────────────────────────────────
+function buildDPSteps(rawValue: string, target: "whole" | "1dp" | "2dp"): Step[] {
+  const value = parseFloat(rawValue);
+  const digits = getDigits(rawValue);
+  const dotIndex = digits.indexOf(".");
+  const steps: Step[] = [];
+
+  function makeDigits(
+    targetIdx: number | null,
+    deciderIdx: number | null,
+  ): DigitInfo[] {
+    return digits.map((ch, i) => ({
+      char: ch,
+      state:
+        ch === "."
+          ? "normal"
+          : i === targetIdx
+            ? "target"
+            : i === deciderIdx
+              ? "decider"
+              : "normal",
+    }));
+  }
+
+  let targetDigitIdx: number;
+  let roundedValue: number;
+  let targetLabel: string;
+
+  if (target === "whole") {
+    targetDigitIdx = dotIndex === -1 ? digits.length - 1 : dotIndex - 1;
+    roundedValue = Math.round(value);
+    targetLabel = "ones (whole number)";
+  } else if (target === "1dp") {
+    targetDigitIdx = dotIndex + 1;
+    roundedValue = Math.round(value * 10) / 10;
+    targetLabel = "1 decimal place (tenths)";
+  } else {
+    targetDigitIdx = dotIndex + 2;
+    roundedValue = Math.round(value * 100) / 100;
+    targetLabel = "2 decimal places (hundredths)";
+  }
+
+  // Compute decider index (skip over decimal point if needed)
+  const nextIdx = targetDigitIdx + 1;
+  const deciderIdx =
+    nextIdx < digits.length && digits[nextIdx] === "."
+      ? nextIdx + 1
+      : nextIdx;
+
+  // Step 0: Show the number
+  steps.push({
+    label: `Rounding ${rawValue} to ${targetLabel}`,
+    digits: makeDigits(null, null),
+  });
+
+  // Step 1: Identify target
+  steps.push({
+    label: `Identify the target digit (${targetLabel})`,
+    digits: makeDigits(targetDigitIdx, null),
+  });
+
+  // Step 2: Identify decider
+  if (deciderIdx < digits.length) {
+    steps.push({
+      label: "Look at the digit to the right (the decider)",
+      digits: makeDigits(targetDigitIdx, deciderIdx),
+    });
+
+    const deciderDigit = parseInt(digits[deciderIdx]);
+    const roundsUp = deciderDigit >= 5;
+    steps.push({
+      label: roundsUp
+        ? `Decider is ${deciderDigit} (≥ 5) → round UP`
+        : `Decider is ${deciderDigit} (< 5) → round DOWN`,
+      digits: makeDigits(targetDigitIdx, deciderIdx),
+    });
+  } else {
+    steps.push({
+      label: "No digit to the right — no rounding needed",
+      digits: makeDigits(targetDigitIdx, null),
+    });
+  }
+
+  // Step 3: Result
+  const resultStr =
+    target === "whole"
+      ? roundedValue.toString()
+      : target === "1dp"
+        ? roundedValue.toFixed(1)
+        : roundedValue.toFixed(2);
+
+  const resultDigits = getDigits(resultStr);
+  steps.push({
+    label: `Result: ${resultStr}`,
+    digits: resultDigits.map((ch) => ({
+      char: ch,
+      state: "normal" as const,
+    })),
+    resultText: resultStr,
+  });
+
+  return steps;
+}
+
+// ── Significant figures rounding steps ───────────────────────────────────────
+function buildSFSteps(rawValue: string, sfCount: number): Step[] {
+  const value = parseFloat(rawValue);
+  const digits = getDigits(rawValue);
+  const steps: Step[] = [];
+
+  // Step 0: Show the number
+  steps.push({
+    label: `Rounding ${rawValue} to ${sfCount} significant figure${sfCount > 1 ? "s" : ""}`,
+    digits: digits.map((ch) => ({ char: ch, state: "normal" as const })),
+  });
+
+  // Step 1: Identify which digits are significant
+  // Rule: significant figures start at the first non-zero digit
+  const sigDigitIndices: number[] = [];
+  let foundFirstNonZero = false;
+  for (let i = 0; i < digits.length; i++) {
+    if (digits[i] === ".") continue;
+    if (!foundFirstNonZero && digits[i] === "0") continue;
+    foundFirstNonZero = true;
+    sigDigitIndices.push(i);
+  }
+
+  // Build display: highlight all significant digits found
+  const sigSet = new Set(sigDigitIndices);
+  steps.push({
+    label: `Identify significant figures — start from the first non-zero digit`,
+    digits: digits.map((ch, i) => ({
+      char: ch,
+      state:
+        ch === "."
+          ? "normal"
+          : sigSet.has(i)
+            ? "significant"
+            : "dim",
+    })),
+  });
+
+  // Count and label the sig figs we need
+  const sigLabel = sigDigitIndices.slice(0, sfCount).map((idx, n) => {
+    return `${ordinal(n + 1)} s.f. = ${digits[idx]}`;
+  });
+  const targetIdx = sigDigitIndices[sfCount - 1]; // the last sig fig we keep
+
+  if (targetIdx === undefined) {
+    // Not enough significant figures in the number
+    steps.push({
+      label: `The number only has ${sigDigitIndices.length} significant figure${sigDigitIndices.length !== 1 ? "s" : ""} — already rounded`,
+      digits: digits.map((ch, i) => ({
+        char: ch,
+        state:
+          ch === "."
+            ? "normal"
+            : sigSet.has(i)
+              ? "significant"
+              : "dim",
+      })),
+      resultText: rawValue,
+    });
+    return steps;
+  }
+
+  // Step 2: Show which sig figs we're keeping
+  const keepSet = new Set(sigDigitIndices.slice(0, sfCount));
+  steps.push({
+    label: `Keep ${sfCount} sig fig${sfCount > 1 ? "s" : ""}: ${sigLabel.join(", ")}`,
+    digits: digits.map((ch, i) => ({
+      char: ch,
+      state:
+        ch === "."
+          ? "normal"
+          : keepSet.has(i)
+            ? "target"
+            : sigSet.has(i)
+              ? "normal"
+              : "dim",
+    })),
+  });
+
+  // Step 3: Identify the decider
+  const deciderCandidateIdx = sigDigitIndices[sfCount]; // next sig fig after the ones we keep
+  // But the decider could also be after a decimal point
+  let deciderIdx: number | null = null;
+  if (deciderCandidateIdx !== undefined) {
+    deciderIdx = deciderCandidateIdx;
+  } else {
+    // Look for any digit after the target
+    for (let i = targetIdx + 1; i < digits.length; i++) {
+      if (digits[i] !== ".") {
+        deciderIdx = i;
+        break;
+      }
+    }
+  }
+
+  if (deciderIdx !== null && deciderIdx < digits.length) {
+    steps.push({
+      label: `Look at the next digit: ${digits[deciderIdx]} (the decider)`,
+      digits: digits.map((ch, i) => ({
+        char: ch,
+        state:
+          ch === "."
+            ? "normal"
+            : i === deciderIdx
+              ? "decider"
+              : keepSet.has(i)
+                ? "target"
+                : "dim",
+      })),
+    });
+
+    // Step 4: Round decision
+    const deciderDigit = parseInt(digits[deciderIdx]);
+    const roundsUp = deciderDigit >= 5;
+    steps.push({
+      label: roundsUp
+        ? `Decider is ${deciderDigit} (≥ 5) → round UP the last kept digit`
+        : `Decider is ${deciderDigit} (< 5) → round DOWN (keep it the same)`,
+      digits: digits.map((ch, i) => ({
+        char: ch,
+        state:
+          ch === "."
+            ? "normal"
+            : i === deciderIdx
+              ? "decider"
+              : keepSet.has(i)
+                ? "target"
+                : "dim",
+      })),
+    });
+  } else {
+    steps.push({
+      label: "No digit to the right — no rounding needed",
+      digits: digits.map((ch, i) => ({
+        char: ch,
+        state:
+          ch === "."
+            ? "normal"
+            : keepSet.has(i)
+              ? "target"
+              : "dim",
+      })),
+    });
+  }
+
+  // Step 5: Compute and show result
+  let roundedValue: number;
+  if (value === 0) {
+    roundedValue = 0;
+  } else {
+    const magnitude = Math.floor(Math.log10(Math.abs(value)));
+    const factor = Math.pow(10, sfCount - 1 - magnitude);
+    roundedValue = Math.round(value * factor) / factor;
+  }
+
+  // Format result with correct sig figs (preserve trailing zeros)
+  const resultStr = formatSigFigs(roundedValue, sfCount);
+  const resultDigits = getDigits(resultStr);
+
+  // Step: explain what happens to remaining digits
+  const dotIdx = rawValue.indexOf(".");
+  const hasIntegerPart = dotIdx === -1 || dotIdx > 0;
+  if (hasIntegerPart && sigDigitIndices.length > sfCount) {
+    // Some trailing digits in the integer part get replaced with zeros
+    steps.push({
+      label: "Replace remaining digits with zeros (to keep the place value)",
+      digits: resultDigits.map((ch) => ({
+        char: ch,
+        state: "normal" as const,
+      })),
+    });
+  }
+
+  steps.push({
+    label: `Result: ${resultStr} (${sfCount} significant figure${sfCount > 1 ? "s" : ""})`,
+    digits: resultDigits.map((ch) => ({
+      char: ch,
+      state: "normal" as const,
+    })),
+    resultText: resultStr,
+  });
+
+  return steps;
+}
+
+function formatSigFigs(value: number, sfCount: number): string {
+  if (value === 0) return "0";
+
+  const magnitude = Math.floor(Math.log10(Math.abs(value)));
+
+  if (magnitude >= sfCount - 1) {
+    // Integer result — no decimal point needed
+    return Math.round(value / Math.pow(10, magnitude - sfCount + 1))
+      * Math.pow(10, magnitude - sfCount + 1) + "";
+  }
+
+  // Decimal result — need to show enough places
+  const decimalPlaces = sfCount - 1 - magnitude;
+  return value.toFixed(decimalPlaces);
+}
+
+function ordinal(n: number): string {
+  if (n === 1) return "1st";
+  if (n === 2) return "2nd";
+  if (n === 3) return "3rd";
+  return `${n}th`;
+}
+
+// ── Main step builder ────────────────────────────────────────────────────────
+function buildSteps(rawValue: string, target: RoundTarget): Step[] {
+  if (target === "whole" || target === "1dp" || target === "2dp") {
+    return buildDPSteps(rawValue, target);
+  }
+  const sfCount = target === "1sf" ? 1 : target === "2sf" ? 2 : 3;
+  return buildSFSteps(rawValue, sfCount);
+}
+
+// ── Digit box component ─────────────────────────────────────────────────────
+function DigitBox({ char, state }: DigitInfo) {
+  if (char === ".") {
+    return (
+      <div className="flex h-[88px] w-6 items-end justify-center pb-2 max-sm:h-[70px]">
+        <div className="h-3 w-3 rounded-full bg-foreground" />
+      </div>
+    );
+  }
+
+  const styles: Record<DigitInfo["state"], string> = {
+    normal: "border-border bg-surface text-foreground",
+    target: "border-unit-2 bg-unit-2-light text-foreground ring-2 ring-unit-2/30",
+    decider: "border-hint bg-hint-light text-foreground ring-2 ring-hint/30",
+    significant: "border-unit-4 bg-unit-4-light text-foreground ring-2 ring-unit-4/30",
+    dim: "border-border/40 bg-background text-muted/30",
+  };
+
+  return (
+    <div
+      className={`flex h-[88px] w-[68px] shrink-0 select-none items-center justify-center rounded-xl border-2 text-[3.2rem] font-bold transition-all duration-300 max-sm:h-[70px] max-sm:w-[52px] max-sm:text-[2.4rem] ${styles[state]}`}
+    >
+      {char}
+    </div>
+  );
+}
+
+// ── Explorer component ──────────────────────────────────────────────────────
+export function RoundingExplorer() {
+  const [input, setInput] = useState("3.4567");
+  const [target, setTarget] = useState<RoundTarget>("1dp");
+  const [error, setError] = useState("");
+
+  const [steps, setSteps] = useState<Step[] | null>(null);
+  const [currentStep, setCurrentStep] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+
+  const done = steps ? currentStep >= steps.length - 1 : false;
+
+  function handleGo() {
+    setError("");
+    const trimmed = input.trim();
+    const val = parseFloat(trimmed);
+    if (isNaN(val)) {
+      setError("Enter a valid number.");
+      return;
+    }
+    if (val < 0) {
+      setError("Enter a positive number.");
+      return;
+    }
+    if (trimmed.length > 16) {
+      setError("Number too long.");
+      return;
+    }
+    if (!trimmed.includes(".") && (target === "1dp" || target === "2dp")) {
+      setError("Enter a decimal number for decimal place rounding.");
+      return;
+    }
+    try {
+      const s = buildSteps(trimmed, target);
+      setSteps(s);
+      setCurrentStep(0);
+      setIsPlaying(false);
+    } catch {
+      setError("Could not process. Check your input.");
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!steps || currentStep >= steps.length - 1) return;
+    setCurrentStep((s) => s + 1);
+    if (currentStep + 1 >= steps.length - 1) setIsPlaying(false);
+  }, [steps, currentStep]);
+
+  const stepBack = useCallback(() => {
+    if (currentStep <= 0) return;
+    setCurrentStep((s) => s - 1);
+  }, [currentStep]);
+
+  const togglePlay = useCallback(() => setIsPlaying((p) => !p), []);
+
+  const reset = useCallback(() => {
+    setSteps(null);
+    setCurrentStep(0);
+    setIsPlaying(false);
+  }, []);
+
+  const step = steps ? steps[currentStep] : null;
+
+  const targetLabels: Record<RoundTarget, string> = {
+    whole: "Whole Number",
+    "1dp": "1 d.p.",
+    "2dp": "2 d.p.",
+    "1sf": "1 s.f.",
+    "2sf": "2 s.f.",
+    "3sf": "3 s.f.",
+  };
+
+  return (
+    <div className="space-y-4">
+      {/* Target tabs */}
+      <div className="flex flex-wrap gap-2">
+        {(["whole", "1dp", "2dp", "1sf", "2sf", "3sf"] as RoundTarget[]).map((t) => (
+          <button
+            key={t}
+            onClick={() => {
+              setTarget(t);
+              reset();
+            }}
+            className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+              target === t
+                ? "border-unit-2 bg-unit-2 text-white"
+                : "border-unit-2/40 text-unit-2 hover:bg-unit-2-light"
+            }`}
+          >
+            {targetLabels[t]}
+          </button>
+        ))}
+      </div>
+
+      {/* Input */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-2">
+          Enter a number
+        </p>
+        <div className="flex flex-wrap items-center gap-2.5">
+          <input
+            type="text"
+            value={input}
+            onChange={(e) => setInput(e.target.value)}
+            onKeyDown={(e) => e.key === "Enter" && handleGo()}
+            placeholder="e.g. 3.4567 or 0.00456"
+            maxLength={18}
+            autoComplete="off"
+            className="max-w-[240px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-2"
+          />
+          <button
+            onClick={handleGo}
+            className="rounded-lg bg-unit-2 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-2-dark"
+          >
+            Round →
+          </button>
+        </div>
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display */}
+      <Card className="flex min-h-[220px] flex-col items-center justify-center gap-4 p-6">
+        {!step ? (
+          <p className="text-muted/50">
+            Enter a number above and click <strong>Round</strong>
+          </p>
+        ) : (
+          <>
+            <p className="text-sm font-medium text-muted">{step.label}</p>
+            <div className="flex flex-wrap items-end justify-center gap-2">
+              {step.digits.map((d, i) => (
+                <DigitBox key={i} {...d} />
+              ))}
+            </div>
+            {/* Legend */}
+            <div className="flex flex-wrap items-center justify-center gap-4 text-xs text-muted">
+              <span className="flex items-center gap-1">
+                <span className="inline-block h-3 w-3 rounded border-2 border-unit-2 bg-unit-2-light" />
+                Target digit
+              </span>
+              <span className="flex items-center gap-1">
+                <span className="inline-block h-3 w-3 rounded border-2 border-hint bg-hint-light" />
+                Decider digit
+              </span>
+              <span className="flex items-center gap-1">
+                <span className="inline-block h-3 w-3 rounded border-2 border-unit-4 bg-unit-4-light" />
+                Significant
+              </span>
+              <span className="flex items-center gap-1">
+                <span className="inline-block h-3 w-3 rounded border-2 border-border/40 bg-background" />
+                Not significant
+              </span>
+            </div>
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep + 1}
+          totalSteps={steps?.length ?? 0}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!steps && !done}
+          canStepBack={!!steps && currentStep > 0}
+        />
+      </Card>
+
+      {/* Result */}
+      <Card className="flex min-h-[80px] flex-col items-center justify-center gap-1.5 text-center">
+        {!done || !step?.resultText ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Rounded Value</p>
+            <p className="text-3xl font-extrabold text-foreground max-sm:text-2xl">
+              {step.resultText}
+            </p>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/standard-form-explorer.tsx

@@ -0,0 +1,445 @@
+"use client";
+
+import { useState, useCallback, useRef, useEffect } from "react";
+import { Card } from "@/components/ui/card";
+import { StepControls } from "./step-controls";
+
+type Mode = "toSF" | "toOrd";
+
+interface DisplayState {
+  digits: string[];
+  decimalPos: number;
+  initPos: number;
+  targetPos: number;
+  origPower: number;
+}
+
+function parseOrdinary(raw: string): { digits: string[]; decimalPos: number } {
+  const s = raw.trim().replace(/[\s,]/g, "");
+  if (s.startsWith("-")) throw new Error("Please enter a positive number.");
+  if (!/^\d*\.?\d+$/.test(s) || s === "")
+    throw new Error("Invalid number. Try something like 7438 or 0.0055");
+  if (s.length > 16) throw new Error("Number too long (max 16 digits).");
+
+  const dot = s.indexOf(".");
+  if (dot === -1) {
+    return { digits: s.split(""), decimalPos: s.length };
+  }
+  return {
+    digits: (s.slice(0, dot) + s.slice(dot + 1)).split(""),
+    decimalPos: dot,
+  };
+}
+
+function firstNonZero(digits: string[]): number {
+  return digits.findIndex((d) => d !== "0");
+}
+
+function sfTargetPos(digits: string[]): number {
+  const i = firstNonZero(digits);
+  return i === -1 ? 1 : i + 1;
+}
+
+function buildCoeff(sigDigs: string[]): string {
+  if (sigDigs.length === 0) return "0";
+  if (sigDigs.length === 1) return sigDigs[0] + ".0";
+  const rest = sigDigs.slice(1).join("").replace(/0+$/, "") || "0";
+  return sigDigs[0] + "." + rest;
+}
+
+function buildOrdinary(digits: string[], pos: number): string {
+  let s: string;
+  if (pos <= 0) {
+    s = "0." + "0".repeat(-pos) + digits.join("");
+  } else if (pos >= digits.length) {
+    s = digits.join("") + "0".repeat(pos - digits.length);
+  } else {
+    s = digits.slice(0, pos).join("") + "." + digits.slice(pos).join("");
+  }
+  s = s.replace(/^0+(?=[1-9])/, "");
+  if (s.startsWith(".")) s = "0" + s;
+  if (s.includes(".")) s = s.replace(/\.?0+$/, "");
+  return s || "0";
+}
+
+export function StandardFormExplorer() {
+  const [mode, setMode] = useState<Mode>("toSF");
+  const [ordinaryInput, setOrdinaryInput] = useState("");
+  const [coeffInput, setCoeffInput] = useState("");
+  const [powerInput, setPowerInput] = useState("");
+  const [error, setError] = useState("");
+
+  const [display, setDisplay] = useState<DisplayState | null>(null);
+  const [currentPos, setCurrentPos] = useState(0);
+  const [isPlaying, setIsPlaying] = useState(false);
+  const [done, setDone] = useState(false);
+
+  const numberRowRef = useRef<HTMLDivElement>(null);
+  const dotRef = useRef<HTMLDivElement>(null);
+  const [dotLeft, setDotLeft] = useState(0);
+  const [dotAnimate, setDotAnimate] = useState(false);
+  const [powerPop, setPowerPop] = useState(false);
+
+  const totalSteps = display ? Math.abs(display.targetPos - display.initPos) : 0;
+  const currentStep = display ? Math.abs(currentPos - display.initPos) : 0;
+
+  const currentPower = display
+    ? mode === "toSF"
+      ? display.initPos - currentPos
+      : display.origPower - (currentPos - display.initPos)
+    : 0;
+
+  // Position decimal dot
+  const placeDot = useCallback(
+    (animate: boolean) => {
+      if (!numberRowRef.current || !display) return;
+      const boxes = numberRowRef.current.querySelectorAll<HTMLDivElement>("[data-digit-box]");
+      if (!boxes.length) return;
+
+      let leftPx: number;
+      const dp = currentPos;
+      if (dp <= 0) {
+        leftPx = boxes[0].offsetLeft - 6;
+      } else if (dp >= boxes.length) {
+        const last = boxes[boxes.length - 1];
+        leftPx = last.offsetLeft + last.offsetWidth - 4;
+      } else {
+        const prev = boxes[dp - 1];
+        const next = boxes[dp];
+        leftPx = Math.round((prev.offsetLeft + prev.offsetWidth + next.offsetLeft) / 2);
+      }
+
+      setDotAnimate(animate);
+      setDotLeft(leftPx);
+    },
+    [currentPos, display],
+  );
+
+  useEffect(() => {
+    if (display) {
+      requestAnimationFrame(() => {
+        requestAnimationFrame(() => placeDot(true));
+      });
+    }
+  }, [currentPos, display, placeDot]);
+
+  // Initial placement without animation
+  useEffect(() => {
+    if (display) {
+      requestAnimationFrame(() => {
+        requestAnimationFrame(() => placeDot(false));
+      });
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [display?.digits.join("")]);
+
+  function initDisplay(digits: string[], start: number, target: number, origPower: number) {
+    setIsPlaying(false);
+    setDone(start === target);
+    setDisplay({ digits, decimalPos: start, initPos: start, targetPos: target, origPower });
+    setCurrentPos(start);
+    setError("");
+  }
+
+  function handleConvertToSF() {
+    setError("");
+    try {
+      const { digits, decimalPos } = parseOrdinary(ordinaryInput);
+      const target = sfTargetPos(digits);
+      initDisplay(digits, decimalPos, target, 0);
+    } catch (e) {
+      setError((e as Error).message);
+    }
+  }
+
+  function handleConvertToOrd() {
+    setError("");
+    try {
+      if (!coeffInput.trim()) throw new Error("Enter the coefficient A.");
+      const n = parseInt(powerInput, 10);
+      if (isNaN(n)) throw new Error("Enter the power n as a whole number.");
+      if (Math.abs(n) > 12) throw new Error("Power too large for display (max ±12).");
+      if (n === 0) throw new Error("Power is 0 — the number is already in ordinary form.");
+
+      const { digits } = parseOrdinary(coeffInput);
+      const A = parseFloat(coeffInput);
+      if (isNaN(A) || A < 1 || A >= 10)
+        throw new Error(`Coefficient must satisfy 1 ≤ A < 10 (got ${coeffInput}).`);
+
+      const decimalPos = 1;
+      const expandedDigits = [...digits];
+
+      let startPos: number;
+      let targetPos: number;
+      if (n > 0) {
+        targetPos = decimalPos + n;
+        startPos = decimalPos;
+        while (expandedDigits.length < targetPos) expandedDigits.push("0");
+      } else {
+        const absN = Math.abs(n);
+        const zeros = Array(absN).fill("0");
+        expandedDigits.unshift(...zeros);
+        startPos = decimalPos + absN;
+        targetPos = startPos + n;
+      }
+
+      initDisplay(expandedDigits, startPos, targetPos, n);
+    } catch (e) {
+      setError((e as Error).message);
+    }
+  }
+
+  const stepForward = useCallback(() => {
+    if (!display || currentPos === display.targetPos) return;
+    const dir = display.targetPos > display.initPos ? 1 : -1;
+    const nextPos = currentPos + dir;
+    setCurrentPos(nextPos);
+    setPowerPop(true);
+    setTimeout(() => setPowerPop(false), 300);
+    if (nextPos === display.targetPos) {
+      setDone(true);
+      setIsPlaying(false);
+    }
+  }, [display, currentPos]);
+
+  const stepBack = useCallback(() => {
+    if (!display || currentPos === display.initPos) return;
+    if (done) setDone(false);
+    const dir = display.targetPos > display.initPos ? -1 : 1;
+    setCurrentPos((p) => p + dir);
+    setPowerPop(true);
+    setTimeout(() => setPowerPop(false), 300);
+  }, [display, currentPos, done]);
+
+  const togglePlay = useCallback(() => {
+    setIsPlaying((p) => !p);
+  }, []);
+
+  const reset = useCallback(() => {
+    setIsPlaying(false);
+    setDisplay(null);
+    setDone(false);
+    setError("");
+  }, []);
+
+  // Direction label
+  const remaining = display ? display.targetPos - currentPos : 0;
+  const dirText =
+    !display || done || remaining === 0
+      ? null
+      : remaining < 0
+        ? `← Moving left · ${Math.abs(remaining)} step${Math.abs(remaining) !== 1 ? "s" : ""} remaining`
+        : `→ Moving right · ${remaining} step${remaining !== 1 ? "s" : ""} remaining`;
+
+  // Result
+  const fz = display ? firstNonZero(display.digits) : 0;
+
+  return (
+    <div className="space-y-4">
+      {/* Mode Tabs */}
+      <div className="flex gap-2">
+        <button
+          onClick={() => {
+            setMode("toSF");
+            reset();
+          }}
+          className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+            mode === "toSF"
+              ? "border-unit-2 bg-unit-2 text-white"
+              : "border-unit-2/40 text-unit-2 hover:bg-unit-2-light"
+          }`}
+        >
+          Ordinary → Standard Form
+        </button>
+        <button
+          onClick={() => {
+            setMode("toOrd");
+            reset();
+          }}
+          className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+            mode === "toOrd"
+              ? "border-unit-2 bg-unit-2 text-white"
+              : "border-unit-2/40 text-unit-2 hover:bg-unit-2-light"
+          }`}
+        >
+          Standard Form → Ordinary
+        </button>
+      </div>
+
+      {/* Input Card */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-2">
+          {mode === "toSF" ? "Enter an ordinary number" : "Enter a number in standard form  A × 10ⁿ"}
+        </p>
+        {mode === "toSF" ? (
+          <div className="flex flex-wrap items-center gap-2.5">
+            <input
+              type="text"
+              value={ordinaryInput}
+              onChange={(e) => setOrdinaryInput(e.target.value)}
+              onKeyDown={(e) => e.key === "Enter" && handleConvertToSF()}
+              placeholder="e.g. 7438 or 0.0055"
+              maxLength={18}
+              autoComplete="off"
+              className="max-w-[220px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-2"
+            />
+            <button
+              onClick={handleConvertToSF}
+              className="rounded-lg bg-unit-2 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-2-dark"
+            >
+              Convert →
+            </button>
+          </div>
+        ) : (
+          <div className="flex flex-wrap items-center gap-2.5">
+            <input
+              type="text"
+              value={coeffInput}
+              onChange={(e) => setCoeffInput(e.target.value)}
+              onKeyDown={(e) => e.key === "Enter" && handleConvertToOrd()}
+              placeholder="A  e.g. 3.6"
+              maxLength={12}
+              autoComplete="off"
+              className="max-w-[140px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-2"
+            />
+            <span className="text-lg font-semibold">
+              × 10<sup>n</sup> where n =
+            </span>
+            <input
+              type="number"
+              value={powerInput}
+              onChange={(e) => setPowerInput(e.target.value)}
+              onKeyDown={(e) => e.key === "Enter" && handleConvertToOrd()}
+              placeholder="e.g. 4 or −3"
+              autoComplete="off"
+              className="max-w-[110px] rounded-lg border-2 border-border bg-surface px-3.5 py-2.5 text-lg font-medium outline-none transition-colors focus:border-unit-2"
+            />
+            <button
+              onClick={handleConvertToOrd}
+              className="rounded-lg bg-unit-2 px-6 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-2-dark"
+            >
+              Convert →
+            </button>
+          </div>
+        )}
+        {error && <p className="mt-2 text-sm text-incorrect">{error}</p>}
+      </Card>
+
+      {/* Display Card */}
+      <Card className="flex min-h-[260px] flex-col items-center justify-center gap-3 p-6">
+        {!display ? (
+          <p className="text-muted/50">
+            Enter a number above and click <strong>Convert</strong>
+          </p>
+        ) : (
+          <>
+            {/* Step info */}
+            <p className="text-sm text-muted">
+              {totalSteps === 0
+                ? "Number is already in standard form position — power = 0"
+                : `Step ${currentStep} of ${totalSteps}`}
+            </p>
+
+            {/* Digit row */}
+            <div ref={numberRowRef} className="relative inline-flex items-end gap-2.5 px-4 pb-7 pt-2">
+              {display.digits.map((ch, i) => {
+                const isLeadingZero = i < fz && fz !== -1;
+                const isHighlight = i === display.targetPos - 1;
+                return (
+                  <div
+                    key={i}
+                    data-digit-box
+                    className={`flex h-[88px] w-[68px] shrink-0 select-none items-center justify-center rounded-xl border-2 text-[3.2rem] font-bold transition-all duration-300 max-sm:h-[70px] max-sm:w-[52px] max-sm:text-[2.4rem] ${
+                      isLeadingZero
+                        ? "border-border/60 bg-background text-muted/30"
+                        : isHighlight
+                          ? "border-unit-2 bg-unit-2-light text-foreground"
+                          : "border-border bg-surface text-foreground"
+                    }`}
+                  >
+                    {ch}
+                  </div>
+                );
+              })}
+              {/* Decimal dot */}
+              <div
+                ref={dotRef}
+                className="absolute bottom-1.5 z-10 h-[18px] w-[18px] -translate-x-1/2 rounded-full bg-incorrect shadow-[0_2px_8px_rgba(239,68,68,0.45)]"
+                style={{
+                  left: dotLeft,
+                  transition: dotAnimate ? "left 0.52s cubic-bezier(0.34,1.56,0.64,1), opacity 0.3s" : "none",
+                  opacity: done && currentPos >= display.digits.length ? 0 : 1,
+                }}
+              />
+            </div>
+
+            {/* Direction label */}
+            {dirText && (
+              <p
+                className={`text-sm font-semibold ${
+                  remaining < 0 ? "text-incorrect" : "text-hint"
+                }`}
+              >
+                {dirText}
+              </p>
+            )}
+
+            {/* Power counter */}
+            <div className="flex items-baseline gap-1.5 text-2xl text-muted">
+              <span>×</span>
+              <span className="font-bold text-foreground">10</span>
+              <sup
+                className={`inline-block min-w-[38px] text-2xl font-extrabold text-hint ${
+                  powerPop ? "animate-bounce" : ""
+                }`}
+              >
+                {currentPower}
+              </sup>
+            </div>
+          </>
+        )}
+      </Card>
+
+      {/* Controls */}
+      <Card className="p-4">
+        <StepControls
+          currentStep={currentStep}
+          totalSteps={totalSteps}
+          isPlaying={isPlaying}
+          onStepForward={stepForward}
+          onStepBack={stepBack}
+          onTogglePlay={togglePlay}
+          onReset={reset}
+          canStepForward={!!display && currentPos !== display.targetPos}
+          canStepBack={!!display && currentPos !== display.initPos}
+        />
+      </Card>
+
+      {/* Result Card */}
+      <Card className="flex min-h-[90px] flex-col items-center justify-center gap-1.5 text-center">
+        {!display || !done ? (
+          <p className="text-sm text-muted/40">Result will appear here when steps are complete</p>
+        ) : mode === "toSF" ? (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Standard Form</p>
+            <p className="text-3xl font-extrabold max-sm:text-2xl">
+              <span className="text-foreground">
+                {buildCoeff(display.digits.slice(fz === -1 ? 0 : fz))}
+              </span>
+              <span className="mx-2 text-muted">×</span>
+              <span className="text-foreground">10</span>
+              <sup className="text-xl text-incorrect">{display.initPos - display.targetPos}</sup>
+            </p>
+          </>
+        ) : (
+          <>
+            <p className="text-xs uppercase tracking-wider text-muted">Ordinary Form</p>
+            <p className="text-3xl font-extrabold text-foreground max-sm:text-2xl">
+              {buildOrdinary(display.digits, display.targetPos)}
+            </p>
+          </>
+        )}
+      </Card>
+    </div>
+  );
+}

components/explorers/step-controls.tsx

@@ -0,0 +1,134 @@
+"use client";
+
+import { useEffect, useCallback, useRef } from "react";
+
+interface StepControlsProps {
+  currentStep: number;
+  totalSteps: number;
+  isPlaying: boolean;
+  onStepForward: () => void;
+  onStepBack: () => void;
+  onTogglePlay: () => void;
+  onReset: () => void;
+  canStepForward: boolean;
+  canStepBack: boolean;
+  playIntervalMs?: number;
+}
+
+export function StepControls({
+  currentStep,
+  totalSteps,
+  isPlaying,
+  onStepForward,
+  onStepBack,
+  onTogglePlay,
+  onReset,
+  canStepForward,
+  canStepBack,
+  playIntervalMs = 950,
+}: StepControlsProps) {
+  const timerRef = useRef<ReturnType<typeof setInterval> | null>(null);
+
+  // Auto-play timer
+  useEffect(() => {
+    if (isPlaying && canStepForward) {
+      timerRef.current = setInterval(() => {
+        onStepForward();
+      }, playIntervalMs);
+    }
+    return () => {
+      if (timerRef.current) clearInterval(timerRef.current);
+    };
+  }, [isPlaying, canStepForward, onStepForward, playIntervalMs]);
+
+  // Keyboard shortcuts
+  const handleKeyDown = useCallback(
+    (e: KeyboardEvent) => {
+      const tag = (e.target as HTMLElement).tagName;
+      if (["INPUT", "TEXTAREA", "SELECT"].includes(tag)) return;
+
+      if (e.key === "ArrowRight" || e.key === " ") {
+        e.preventDefault();
+        if (canStepForward) onStepForward();
+      }
+      if (e.key === "ArrowLeft") {
+        e.preventDefault();
+        if (canStepBack) onStepBack();
+      }
+      if (e.key.toLowerCase() === "p") onTogglePlay();
+      if (e.key.toLowerCase() === "r") onReset();
+    },
+    [canStepForward, canStepBack, onStepForward, onStepBack, onTogglePlay, onReset],
+  );
+
+  useEffect(() => {
+    document.addEventListener("keydown", handleKeyDown);
+    return () => document.removeEventListener("keydown", handleKeyDown);
+  }, [handleKeyDown]);
+
+  const progress = totalSteps > 0 ? (currentStep / totalSteps) * 100 : 0;
+
+  return (
+    <div className="space-y-3">
+      {/* Progress bar */}
+      {totalSteps > 0 && (
+        <div className="mx-auto max-w-md">
+          <div className="mb-1.5 flex items-center justify-between text-xs text-muted">
+            <span>Step {currentStep} of {totalSteps}</span>
+            <span>{Math.round(progress)}%</span>
+          </div>
+          <div className="h-1.5 overflow-hidden rounded-full bg-border/60">
+            <div
+              className="h-full rounded-full bg-gradient-to-r from-unit-1 to-unit-4 transition-all duration-300"
+              style={{ width: `${progress}%` }}
+            />
+          </div>
+        </div>
+      )}
+
+      {/* Controls */}
+      <div className="flex flex-wrap items-center justify-center gap-2">
+        <button
+          onClick={onStepBack}
+          disabled={!canStepBack || isPlaying}
+          className="rounded-xl border border-border/60 bg-surface px-4 py-2.5 text-sm font-semibold text-foreground shadow-[var(--shadow-sm)] transition-all duration-200 hover:shadow-[var(--shadow-md)] hover:-translate-y-px disabled:cursor-not-allowed disabled:opacity-35 disabled:hover:translate-y-0 disabled:hover:shadow-[var(--shadow-sm)]"
+        >
+          &#9664; Back
+        </button>
+        <button
+          onClick={onTogglePlay}
+          disabled={!canStepForward && !isPlaying}
+          className="min-w-[110px] rounded-xl bg-correct px-5 py-2.5 text-sm font-semibold text-white shadow-[var(--shadow-sm)] transition-all duration-200 hover:shadow-[var(--shadow-md)] hover:-translate-y-px disabled:cursor-not-allowed disabled:opacity-35 disabled:hover:translate-y-0 disabled:hover:shadow-[var(--shadow-sm)]"
+        >
+          {isPlaying ? "⏸ Pause" : "▶ Play"}
+        </button>
+        <button
+          onClick={onStepForward}
+          disabled={!canStepForward || isPlaying}
+          className="rounded-xl bg-foreground px-5 py-2.5 text-sm font-semibold text-background shadow-[var(--shadow-sm)] transition-all duration-200 hover:shadow-[var(--shadow-md)] hover:-translate-y-px disabled:cursor-not-allowed disabled:opacity-35 disabled:hover:translate-y-0 disabled:hover:shadow-[var(--shadow-sm)]"
+        >
+          Next Step &#9654;
+        </button>
+        <button
+          onClick={onReset}
+          className="rounded-xl border border-incorrect/30 bg-surface px-4 py-2.5 text-sm font-semibold text-incorrect shadow-[var(--shadow-sm)] transition-all duration-200 hover:bg-incorrect hover:text-white hover:shadow-[var(--shadow-md)] hover:-translate-y-px"
+        >
+          &#8634; Reset
+        </button>
+      </div>
+
+      {/* Keyboard hint */}
+      <p className="text-center text-[0.7rem] text-muted/50">
+        <kbd className="rounded border border-border/60 bg-background px-1 py-px font-mono text-[0.6rem]">Space</kbd>{" / "}
+        <kbd className="rounded border border-border/60 bg-background px-1 py-px font-mono text-[0.6rem]">&#8594;</kbd>{" "}
+        next{" · "}
+        <kbd className="rounded border border-border/60 bg-background px-1 py-px font-mono text-[0.6rem]">&#8592;</kbd>{" "}
+        back{" · "}
+        <kbd className="rounded border border-border/60 bg-background px-1 py-px font-mono text-[0.6rem]">P</kbd>{" "}
+        play{" · "}
+        <kbd className="rounded border border-border/60 bg-background px-1 py-px font-mono text-[0.6rem]">R</kbd>{" "}
+        reset
+      </p>
+    </div>
+  );
+}

components/layout/breadcrumbs.tsx

@@ -0,0 +1,38 @@
+import Link from "next/link";
+
+interface BreadcrumbItem {
+  label: string;
+  href?: string;
+}
+
+interface BreadcrumbsProps {
+  items: BreadcrumbItem[];
+}
+
+export function Breadcrumbs({ items }: BreadcrumbsProps) {
+  return (
+    <nav aria-label="Breadcrumb" className="mb-6">
+      <ol className="flex flex-wrap items-center gap-1.5 text-sm">
+        <li>
+          <Link href="/" className="text-muted transition-colors hover:text-foreground">
+            Home
+          </Link>
+        </li>
+        {items.map((item, i) => (
+          <li key={i} className="flex items-center gap-1.5">
+            <svg className="h-3.5 w-3.5 text-border" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2.5}>
+              <path strokeLinecap="round" strokeLinejoin="round" d="M9 5l7 7-7 7" />
+            </svg>
+            {item.href ? (
+              <Link href={item.href} className="text-muted transition-colors hover:text-foreground">
+                {item.label}
+              </Link>
+            ) : (
+              <span className="font-medium text-foreground">{item.label}</span>
+            )}
+          </li>
+        ))}
+      </ol>
+    </nav>
+  );
+}

components/layout/footer.tsx

@@ -0,0 +1,32 @@
+import Link from "next/link";
+
+export function Footer() {
+  return (
+    <footer className="border-t border-border/60 bg-surface/95">
+      <div className="mx-auto max-w-7xl px-4 py-8 sm:px-6 lg:px-8">
+        <div className="flex flex-col items-center justify-between gap-4 sm:flex-row">
+          <div className="flex items-center gap-3">
+            <div className="flex h-8 w-8 items-center justify-center rounded-xl bg-gradient-to-br from-unit-1 via-unit-2 to-unit-3 shadow-[var(--shadow-sm)]">
+              <span className="text-xs font-extrabold text-white">C</span>
+            </div>
+            <div>
+              <p className="text-sm font-extrabold text-[#17367d]">Cabrits Mathematics</p>
+              <p className="text-xs text-[#4c6290]">Learn it. Try it. Master it.</p>
+            </div>
+          </div>
+          <nav className="flex items-center gap-5 text-sm font-semibold text-muted">
+            <Link href="/lessons" className="transition-colors hover:text-foreground">
+              Lessons
+            </Link>
+            <Link href="/practice" className="transition-colors hover:text-foreground">
+              Practice
+            </Link>
+          </nav>
+          <p className="text-xs font-medium text-muted">
+            Portsmouth Secondary School
+          </p>
+        </div>
+      </div>
+    </footer>
+  );
+}

components/layout/header.tsx

@@ -0,0 +1,42 @@
+import Link from "next/link";
+
+const navItems = [
+  { href: "/", label: "Home", className: "bg-[#e0483d] hover:bg-[#cb3a30]" },
+  { href: "/lessons", label: "Lessons", className: "bg-[#f08b24] hover:bg-[#d97706]" },
+  { href: "/practice", label: "Practice", className: "bg-[#1faa59] hover:bg-[#168845]" },
+];
+
+export function Header() {
+  return (
+    <header className="sticky top-0 z-50 border-b-4 border-[#1c4ab7] bg-[#2f65e8] text-white">
+      <div className="mx-auto max-w-6xl playground-frame border-b-0 border-t-0 bg-[#2f65e8] shadow-none">
+        <div className="flex flex-wrap items-center justify-between gap-3 px-4 py-3">
+          <Link href="/" className="group flex items-center gap-3">
+            <div className="flex h-10 w-10 items-center justify-center rounded-lg bg-[#ffd043] text-[#10308a] shadow-md">
+              <span className="text-lg font-extrabold">C</span>
+            </div>
+            <div className="rounded-md bg-white px-2.5 py-1 leading-none shadow-sm">
+              <p className="text-2xl font-extrabold tracking-tight text-[#17367d]">Cabrits</p>
+              <p className="text-xs font-bold uppercase tracking-[0.14em] text-[#3a5ea8]">Math Playground</p>
+            </div>
+          </Link>
+          <div className="flex items-center gap-2 text-xs font-bold sm:text-sm">
+            <span className="rounded-full bg-[#1a49b6] px-3 py-1">Ages 12-16</span>
+            <span className="rounded-full bg-[#1a49b6] px-3 py-1">Form 1 Term 2</span>
+          </div>
+        </div>
+        <nav className="flex flex-wrap gap-1 bg-[#1b49b5] px-2 pb-2 pt-1">
+          {navItems.map((item) => (
+            <Link
+              key={item.href}
+              href={item.href}
+              className={`rounded-sm px-4 py-2 text-sm font-extrabold text-white transition-colors ${item.className}`}
+            >
+              {item.label}
+            </Link>
+          ))}
+        </nav>
+      </div>
+    </header>
+  );
+}

components/layout/mobile-nav.tsx

@@ -0,0 +1,89 @@
+"use client";
+
+import Link from "next/link";
+import { usePathname } from "next/navigation";
+import { curriculum } from "@/lib/curriculum";
+import { cn } from "@/lib/utils";
+import { useState } from "react";
+
+const unitColorMap = {
+  "unit-1": "text-unit-1-dark",
+  "unit-2": "text-unit-2-dark",
+  "unit-3": "text-unit-3-dark",
+  "unit-4": "text-unit-4-dark",
+};
+
+const unitDotColor = {
+  "unit-1": "bg-unit-1",
+  "unit-2": "bg-unit-2",
+  "unit-3": "bg-unit-3",
+  "unit-4": "bg-unit-4",
+};
+
+export function MobileNav() {
+  const pathname = usePathname();
+  const [isOpen, setIsOpen] = useState(false);
+
+  return (
+    <div className="lg:hidden">
+      <button
+        onClick={() => setIsOpen(!isOpen)}
+        className="flex items-center gap-2 rounded-xl border border-border/60 bg-surface px-3.5 py-2 text-sm font-medium shadow-[var(--shadow-sm)] transition-all hover:shadow-[var(--shadow-md)]"
+        aria-label="Toggle navigation"
+      >
+        <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+          {isOpen ? (
+            <path strokeLinecap="round" strokeLinejoin="round" d="M6 18L18 6M6 6l12 12" />
+          ) : (
+            <path strokeLinecap="round" strokeLinejoin="round" d="M4 6h16M4 12h16M4 18h16" />
+          )}
+        </svg>
+        Topics
+      </button>
+
+      {isOpen && (
+        <div className="absolute left-0 right-0 top-full z-40 max-h-[70vh] overflow-y-auto border-b border-border/60 bg-surface p-4 shadow-[var(--shadow-lg)]">
+          <Link
+            href="/lessons"
+            onClick={() => setIsOpen(false)}
+            className="mb-4 flex items-center gap-2 rounded-xl px-3 py-2 text-sm font-medium text-muted transition-colors hover:bg-background hover:text-foreground"
+          >
+            <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+              <path strokeLinecap="round" strokeLinejoin="round" d="M4 6h16M4 10h16M4 14h16M4 18h16" />
+            </svg>
+            All Topics
+          </Link>
+          <div className="mb-3 h-px bg-border/60" />
+          {curriculum.map((unit) => (
+            <div key={unit.slug} className="mb-4">
+              <p className={cn("mb-1.5 flex items-center gap-2 px-3 text-xs font-bold uppercase tracking-wider", unitColorMap[unit.color])}>
+                <span className={cn("h-2 w-2 rounded-full", unitDotColor[unit.color])} />
+                Unit {unit.number}: {unit.title}
+              </p>
+              <div className="space-y-0.5">
+                {unit.topics.map((topic) => {
+                  const href = `/lessons/${unit.slug}/${topic.slug}`;
+                  return (
+                    <Link
+                      key={topic.slug}
+                      href={href}
+                      onClick={() => setIsOpen(false)}
+                      className={cn(
+                        "block rounded-lg px-3 py-1.5 text-sm transition-colors",
+                        pathname === href
+                          ? "bg-foreground text-background font-medium"
+                          : "text-muted hover:bg-background hover:text-foreground",
+                      )}
+                    >
+                      {topic.shortTitle}
+                    </Link>
+                  );
+                })}
+              </div>
+            </div>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}

components/layout/sidebar.tsx

@@ -0,0 +1,142 @@
+"use client";
+
+import Link from "next/link";
+import { usePathname } from "next/navigation";
+import { curriculum } from "@/lib/curriculum";
+import { cn } from "@/lib/utils";
+import { useState } from "react";
+
+const unitColorMap = {
+  "unit-1": {
+    active: "bg-unit-1-light text-unit-1-dark border-unit-1/20",
+    dot: "bg-unit-1",
+    heading: "text-unit-1-dark",
+    hoverBg: "hover:bg-unit-1-light/50",
+  },
+  "unit-2": {
+    active: "bg-unit-2-light text-unit-2-dark border-unit-2/20",
+    dot: "bg-unit-2",
+    heading: "text-unit-2-dark",
+    hoverBg: "hover:bg-unit-2-light/50",
+  },
+  "unit-3": {
+    active: "bg-unit-3-light text-unit-3-dark border-unit-3/20",
+    dot: "bg-unit-3",
+    heading: "text-unit-3-dark",
+    hoverBg: "hover:bg-unit-3-light/50",
+  },
+  "unit-4": {
+    active: "bg-unit-4-light text-unit-4-dark border-unit-4/20",
+    dot: "bg-unit-4",
+    heading: "text-unit-4-dark",
+    hoverBg: "hover:bg-unit-4-light/50",
+  },
+};
+
+export function Sidebar() {
+  const pathname = usePathname();
+  const [openUnits, setOpenUnits] = useState<Set<number>>(() => {
+    const open = new Set<number>();
+    for (const unit of curriculum) {
+      if (pathname.includes(unit.slug)) {
+        open.add(unit.number);
+      }
+    }
+    if (open.size === 0) open.add(1);
+    return open;
+  });
+
+  function toggleUnit(num: number) {
+    setOpenUnits((prev) => {
+      const next = new Set(prev);
+      if (next.has(num)) next.delete(num);
+      else next.add(num);
+      return next;
+    });
+  }
+
+  return (
+    <aside className="hidden w-64 shrink-0 border-r border-border/60 bg-surface lg:block">
+      <nav className="sticky top-[4.125rem] h-[calc(100vh-4.125rem)] overflow-y-auto p-4">
+        <Link
+          href="/lessons"
+          className={cn(
+            "mb-4 flex items-center gap-2 rounded-xl px-3 py-2 text-sm font-medium transition-all duration-200",
+            pathname === "/lessons"
+              ? "bg-foreground text-background shadow-[var(--shadow-sm)]"
+              : "text-muted hover:bg-background hover:text-foreground",
+          )}
+        >
+          <svg className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+            <path strokeLinecap="round" strokeLinejoin="round" d="M4 6h16M4 10h16M4 14h16M4 18h16" />
+          </svg>
+          All Topics
+        </Link>
+
+        <div className="mb-3 h-px bg-border/60" />
+
+        {curriculum.map((unit) => {
+          const colors = unitColorMap[unit.color];
+          const isOpen = openUnits.has(unit.number);
+
+          return (
+            <div key={unit.slug} className="mb-1">
+              <button
+                onClick={() => toggleUnit(unit.number)}
+                className={cn(
+                  "flex w-full items-center justify-between rounded-xl px-3 py-2 text-left text-sm font-semibold transition-all duration-200",
+                  colors.heading,
+                  colors.hoverBg,
+                )}
+              >
+                <span className="truncate">Unit {unit.number}: {unit.title}</span>
+                <svg
+                  className={cn(
+                    "h-4 w-4 shrink-0 transition-transform duration-200",
+                    isOpen && "rotate-90",
+                  )}
+                  fill="none"
+                  viewBox="0 0 24 24"
+                  stroke="currentColor"
+                  strokeWidth={2}
+                >
+                  <path strokeLinecap="round" strokeLinejoin="round" d="M9 5l7 7-7 7" />
+                </svg>
+              </button>
+
+              {isOpen && (
+                <div className="ml-2 mt-0.5 space-y-0.5 border-l-2 border-border/40 pl-2">
+                  {unit.topics.map((topic) => {
+                    const href = `/lessons/${unit.slug}/${topic.slug}`;
+                    const isActive = pathname === href;
+
+                    return (
+                      <Link
+                        key={topic.slug}
+                        href={href}
+                        className={cn(
+                          "flex items-center gap-2 rounded-lg px-2.5 py-1.5 text-sm transition-all duration-200",
+                          isActive
+                            ? cn(colors.active, "font-medium shadow-[var(--shadow-sm)]")
+                            : "text-muted hover:text-foreground",
+                        )}
+                      >
+                        <span
+                          className={cn(
+                            "h-1.5 w-1.5 shrink-0 rounded-full transition-colors",
+                            isActive ? colors.dot : "bg-border",
+                          )}
+                        />
+                        <span className="truncate">{topic.shortTitle}</span>
+                      </Link>
+                    );
+                  })}
+                </div>
+              )}
+            </div>
+          );
+        })}
+      </nav>
+    </aside>
+  );
+}

components/math/math-display.tsx

@@ -0,0 +1,36 @@
+"use client";
+
+import katex from "katex";
+
+interface MathDisplayProps {
+  math: string;
+  className?: string;
+}
+
+export function MathDisplay({ math, className }: MathDisplayProps) {
+  const html = katex.renderToString(math, {
+    displayMode: true,
+    throwOnError: false,
+  });
+
+  return (
+    <div
+      className={className}
+      dangerouslySetInnerHTML={{ __html: html }}
+    />
+  );
+}
+
+export function MathInline({ math, className }: MathDisplayProps) {
+  const html = katex.renderToString(math, {
+    displayMode: false,
+    throwOnError: false,
+  });
+
+  return (
+    <span
+      className={className}
+      dangerouslySetInnerHTML={{ __html: html }}
+    />
+  );
+}

components/practice/fraction-input.tsx

@@ -0,0 +1,104 @@
+"use client";
+
+import { cn } from "@/lib/utils";
+
+interface FractionInputProps {
+  numerator: string;
+  denominator: string;
+  onNumeratorChange: (value: string) => void;
+  onDenominatorChange: (value: string) => void;
+  disabled?: boolean;
+  className?: string;
+}
+
+export function FractionInput({
+  numerator,
+  denominator,
+  onNumeratorChange,
+  onDenominatorChange,
+  disabled = false,
+  className,
+}: FractionInputProps) {
+  return (
+    <div className={cn("inline-flex flex-col items-center gap-0.5", className)}>
+      <input
+        type="text"
+        inputMode="numeric"
+        pattern="[0-9-]*"
+        value={numerator}
+        onChange={(e) => onNumeratorChange(e.target.value)}
+        disabled={disabled}
+        className="w-16 rounded-lg border border-border bg-surface px-2 py-1.5 text-center text-lg font-bold focus:border-unit-1 focus:outline-none"
+        placeholder="?"
+        aria-label="Numerator"
+      />
+      <div className="h-0.5 w-16 bg-foreground" />
+      <input
+        type="text"
+        inputMode="numeric"
+        pattern="[0-9-]*"
+        value={denominator}
+        onChange={(e) => onDenominatorChange(e.target.value)}
+        disabled={disabled}
+        className="w-16 rounded-lg border border-border bg-surface px-2 py-1.5 text-center text-lg font-bold focus:border-unit-1 focus:outline-none"
+        placeholder="?"
+        aria-label="Denominator"
+      />
+    </div>
+  );
+}
+
+interface DecimalInputProps {
+  value: string;
+  onChange: (value: string) => void;
+  disabled?: boolean;
+  className?: string;
+}
+
+export function DecimalInput({ value, onChange, disabled, className }: DecimalInputProps) {
+  return (
+    <input
+      type="text"
+      inputMode="decimal"
+      value={value}
+      onChange={(e) => onChange(e.target.value)}
+      disabled={disabled}
+      className={cn(
+        "w-28 rounded-lg border border-border bg-surface px-3 py-2 text-center text-lg font-bold focus:border-unit-2 focus:outline-none",
+        className,
+      )}
+      placeholder="?"
+      aria-label="Answer"
+    />
+  );
+}
+
+interface RatioInputProps {
+  parts: string[];
+  onChange: (index: number, value: string) => void;
+  disabled?: boolean;
+  className?: string;
+}
+
+export function RatioInput({ parts, onChange, disabled, className }: RatioInputProps) {
+  return (
+    <div className={cn("inline-flex items-center gap-1", className)}>
+      {parts.map((p, i) => (
+        <span key={i} className="flex items-center gap-1">
+          {i > 0 && <span className="text-lg font-bold text-muted">:</span>}
+          <input
+            type="text"
+            inputMode="numeric"
+            pattern="[0-9]*"
+            value={p}
+            onChange={(e) => onChange(i, e.target.value)}
+            disabled={disabled}
+            className="w-14 rounded-lg border border-border bg-surface px-2 py-2 text-center text-lg font-bold focus:border-unit-4 focus:outline-none"
+            placeholder="?"
+            aria-label={`Part ${i + 1}`}
+          />
+        </span>
+      ))}
+    </div>
+  );
+}

components/practice/practice-section.tsx

@@ -0,0 +1,308 @@
+"use client";
+
+import { useState, useCallback } from "react";
+import { motion, AnimatePresence } from "framer-motion";
+import type { MathProblem, Difficulty } from "@/lib/problems/types";
+import { checkFractionAnswer, checkDecimalAnswer, checkRatioAnswer, checkIntegerAnswer, type AnswerResult } from "@/lib/math/validation";
+import { FractionInput, DecimalInput, RatioInput } from "./fraction-input";
+import { Button } from "@/components/ui/button";
+import { Card } from "@/components/ui/card";
+import katex from "katex";
+
+interface PracticeSectionProps {
+  title: string;
+  generator: (difficulty: Difficulty) => MathProblem;
+  unitColor?: "unit-1" | "unit-2" | "unit-3" | "unit-4";
+}
+
+type UnitColor = NonNullable<PracticeSectionProps["unitColor"]>;
+
+const activeDifficultyStyle: Record<UnitColor, string> = {
+  "unit-1": "bg-unit-1 text-white",
+  "unit-2": "bg-unit-2 text-white",
+  "unit-3": "bg-unit-3 text-white",
+  "unit-4": "bg-unit-4 text-white",
+};
+
+export function PracticeSection({ title, generator, unitColor = "unit-1" }: PracticeSectionProps) {
+  const [difficulty, setDifficulty] = useState<Difficulty>(1);
+  const [problem, setProblem] = useState<MathProblem>(() => generator(1));
+  const [userAnswer, setUserAnswer] = useState<Record<string, string>>({});
+  const [result, setResult] = useState<AnswerResult | null>(null);
+  const [showHint, setShowHint] = useState(false);
+  const [hintIndex, setHintIndex] = useState(0);
+  const [showSolution, setShowSolution] = useState(false);
+  const [score, setScore] = useState({ correct: 0, total: 0 });
+
+  const generateNew = useCallback((diff: Difficulty) => {
+    setProblem(generator(diff));
+    setUserAnswer({});
+    setResult(null);
+    setShowHint(false);
+    setHintIndex(0);
+    setShowSolution(false);
+  }, [generator]);
+
+  function checkAnswer() {
+    const answer = problem.answer;
+    let res: AnswerResult;
+
+    switch (answer.kind) {
+      case "fraction": {
+        const num = parseInt(userAnswer.numerator || "0");
+        const den = parseInt(userAnswer.denominator || "0");
+        if (isNaN(num) || isNaN(den)) {
+          res = { correct: false, message: "Enter valid numbers" };
+        } else {
+          res = checkFractionAnswer(num, den, answer.numerator, answer.denominator);
+        }
+        break;
+      }
+      case "decimal": {
+        const val = parseFloat(userAnswer.value || "");
+        if (isNaN(val)) {
+          res = { correct: false, message: "Enter a valid number" };
+        } else {
+          res = checkDecimalAnswer(val, answer.value);
+        }
+        break;
+      }
+      case "integer": {
+        const val = parseInt(userAnswer.value || "");
+        if (isNaN(val)) {
+          res = { correct: false, message: "Enter a valid number" };
+        } else {
+          res = checkIntegerAnswer(val, answer.value);
+        }
+        break;
+      }
+      case "ratio": {
+        const parts = (userAnswer.ratio || "").split(":").map((p) => parseInt(p.trim()));
+        if (parts.some(isNaN)) {
+          res = { correct: false, message: "Enter valid ratio parts" };
+        } else {
+          res = checkRatioAnswer(parts, answer.parts);
+        }
+        break;
+      }
+      case "standardForm": {
+        const coeff = parseFloat(userAnswer.coefficient || "");
+        const exp = parseInt(userAnswer.exponent || "");
+        if (isNaN(coeff) || isNaN(exp)) {
+          res = { correct: false, message: "Enter valid numbers" };
+        } else if (
+          Math.abs(coeff - answer.coefficient) < 0.01 &&
+          exp === answer.exponent
+        ) {
+          res = { correct: true, simplified: true };
+        } else {
+          res = { correct: false, message: "That's not quite right. Try again!" };
+        }
+        break;
+      }
+    }
+
+    setResult(res);
+    if (res.correct) {
+      setScore((s) => ({ correct: s.correct + 1, total: s.total + 1 }));
+    } else {
+      setScore((s) => ({ ...s, total: s.total + 1 }));
+    }
+  }
+
+  function nextHint() {
+    if (hintIndex < problem.hints.length - 1) {
+      setHintIndex((i) => i + 1);
+    }
+    setShowHint(true);
+  }
+
+  const promptHtml = katex.renderToString(problem.prompt, { throwOnError: false, displayMode: true });
+
+  return (
+    <Card className="mt-8 border-2">
+      <div className="mb-4 flex items-center justify-between">
+        <h3 className="text-lg font-extrabold">{title}</h3>
+        <div className="flex items-center gap-2 text-sm">
+          <span className="rounded-full bg-background px-2.5 py-1 font-bold text-muted">
+            {score.correct}/{score.total}
+          </span>
+          <div className="flex gap-1">
+            {([1, 2, 3] as Difficulty[]).map((d) => (
+              <button
+                key={d}
+                onClick={() => {
+                  setDifficulty(d);
+                  generateNew(d);
+                }}
+                className={`rounded-lg px-2.5 py-1 text-xs font-extrabold transition-colors ${
+                  difficulty === d
+                    ? activeDifficultyStyle[unitColor]
+                    : "bg-border/70 text-muted hover:bg-border hover:text-foreground"
+                }`}
+              >
+                L{d}
+              </button>
+            ))}
+          </div>
+        </div>
+      </div>
+
+      {/* Problem */}
+      <div
+        className="mb-6 text-center text-xl"
+        dangerouslySetInnerHTML={{ __html: promptHtml }}
+      />
+
+      {/* Input */}
+      <div className="mb-4 flex flex-wrap items-center justify-center gap-4">
+        {problem.answer.kind === "fraction" && (
+          <FractionInput
+            numerator={userAnswer.numerator || ""}
+            denominator={userAnswer.denominator || ""}
+            onNumeratorChange={(v) => setUserAnswer((a) => ({ ...a, numerator: v }))}
+            onDenominatorChange={(v) => setUserAnswer((a) => ({ ...a, denominator: v }))}
+            disabled={result?.correct === true}
+          />
+        )}
+
+        {(problem.answer.kind === "decimal" || problem.answer.kind === "integer") && (
+          <DecimalInput
+            value={userAnswer.value || ""}
+            onChange={(v) => setUserAnswer((a) => ({ ...a, value: v }))}
+            disabled={result?.correct === true}
+          />
+        )}
+
+        {problem.answer.kind === "ratio" && (() => {
+          const ratioParts = (problem.answer as { kind: "ratio"; parts: number[] }).parts;
+          return (
+            <RatioInput
+              parts={
+                userAnswer.ratioParts
+                  ? JSON.parse(userAnswer.ratioParts)
+                  : ratioParts.map(() => "")
+              }
+              onChange={(i, v) => {
+                const current = userAnswer.ratioParts
+                  ? JSON.parse(userAnswer.ratioParts)
+                  : ratioParts.map(() => "");
+                current[i] = v;
+                setUserAnswer((a) => ({
+                  ...a,
+                  ratioParts: JSON.stringify(current),
+                  ratio: current.join(":"),
+                }));
+              }}
+              disabled={result?.correct === true}
+            />
+          );
+        })()}
+
+        {problem.answer.kind === "standardForm" && (
+          <div className="flex items-center gap-1">
+            <input
+              type="text"
+              inputMode="decimal"
+              value={userAnswer.coefficient || ""}
+              onChange={(e) => setUserAnswer((a) => ({ ...a, coefficient: e.target.value }))}
+              disabled={result?.correct === true}
+              className="w-16 rounded-lg border border-border bg-surface px-2 py-2 text-center font-bold focus:border-unit-2 focus:outline-none"
+              placeholder="?"
+              aria-label="Coefficient"
+            />
+            <span className="text-lg font-bold">x 10</span>
+            <input
+              type="text"
+              inputMode="numeric"
+              value={userAnswer.exponent || ""}
+              onChange={(e) => setUserAnswer((a) => ({ ...a, exponent: e.target.value }))}
+              disabled={result?.correct === true}
+              className="w-12 -translate-y-2 rounded-lg border border-border bg-surface px-2 py-1 text-center text-sm font-bold focus:border-unit-2 focus:outline-none"
+              placeholder="?"
+              aria-label="Exponent"
+            />
+          </div>
+        )}
+      </div>
+
+      {/* Actions */}
+      <div className="mb-4 flex flex-wrap justify-center gap-3">
+        {!result?.correct && (
+          <>
+            <Button variant={unitColor} size="sm" onClick={checkAnswer}>
+              Check Answer
+            </Button>
+            <Button variant="secondary" size="sm" onClick={nextHint}>
+              Hint
+            </Button>
+            <Button variant="ghost" size="sm" onClick={() => setShowSolution(true)}>
+              Show Solution
+            </Button>
+          </>
+        )}
+        {result?.correct && (
+          <Button variant={unitColor} size="sm" onClick={() => generateNew(difficulty)}>
+            Next Problem
+          </Button>
+        )}
+      </div>
+
+      {/* Feedback */}
+      <AnimatePresence>
+        {result && (
+          <motion.div
+            initial={{ opacity: 0, y: -10 }}
+            animate={{ opacity: 1, y: 0 }}
+            exit={{ opacity: 0 }}
+            className={`rounded-xl px-4 py-3 text-center text-sm font-medium ${
+              result.correct
+                ? result.simplified
+                  ? "bg-correct-light text-correct"
+                  : "bg-hint-light text-hint"
+                : "bg-incorrect-light text-incorrect"
+            }`}
+          >
+            {result.correct
+              ? result.simplified
+                ? "Correct!"
+                : "Correct, but can you simplify further?"
+              : result.message}
+          </motion.div>
+        )}
+      </AnimatePresence>
+
+      {/* Hint */}
+      <AnimatePresence>
+        {showHint && (
+          <motion.div
+            initial={{ opacity: 0 }}
+            animate={{ opacity: 1 }}
+            className="mt-3 rounded-xl bg-hint-light px-4 py-3 text-sm text-hint"
+          >
+            {problem.hints[hintIndex]}
+          </motion.div>
+        )}
+      </AnimatePresence>
+
+      {/* Solution */}
+      <AnimatePresence>
+        {showSolution && (
+          <motion.div
+            initial={{ opacity: 0, height: 0 }}
+            animate={{ opacity: 1, height: "auto" }}
+            className="mt-3 space-y-2 rounded-xl bg-background p-4"
+          >
+            <p className="text-xs font-semibold uppercase text-muted">Solution</p>
+            {problem.steps.map((step, i) => (
+              <div key={i} className="flex gap-2 text-sm">
+                <span className="shrink-0 font-bold text-muted">{i + 1}.</span>
+                <span>{step.explanation}</span>
+              </div>
+            ))}
+          </motion.div>
+        )}
+      </AnimatePresence>
+    </Card>
+  );
+}

components/ui/badge.tsx

@@ -0,0 +1,31 @@
+import { cn } from "@/lib/utils";
+import { type HTMLAttributes } from "react";
+
+type BadgeVariant = "default" | "unit-1" | "unit-2" | "unit-3" | "unit-4";
+
+interface BadgeProps extends HTMLAttributes<HTMLSpanElement> {
+  variant?: BadgeVariant;
+}
+
+const variantStyles: Record<BadgeVariant, string> = {
+  default: "border border-border/70 bg-background text-muted",
+  "unit-1": "border border-unit-1/20 bg-unit-1-light text-unit-1-dark",
+  "unit-2": "border border-unit-2/20 bg-unit-2-light text-unit-2-dark",
+  "unit-3": "border border-unit-3/20 bg-unit-3-light text-unit-3-dark",
+  "unit-4": "border border-unit-4/20 bg-unit-4-light text-unit-4-dark",
+};
+
+export function Badge({ variant = "default", className, children, ...props }: BadgeProps) {
+  return (
+    <span
+      className={cn(
+        "inline-flex items-center rounded-full px-3 py-1 text-xs font-extrabold tracking-wide",
+        variantStyles[variant],
+        className,
+      )}
+      {...props}
+    >
+      {children}
+    </span>
+  );
+}

components/ui/button.tsx

@@ -0,0 +1,51 @@
+import { cn } from "@/lib/utils";
+import { type ButtonHTMLAttributes } from "react";
+
+type ButtonVariant = "primary" | "secondary" | "ghost" | "unit-1" | "unit-2" | "unit-3" | "unit-4";
+type ButtonSize = "sm" | "md" | "lg";
+
+interface ButtonProps extends ButtonHTMLAttributes<HTMLButtonElement> {
+  variant?: ButtonVariant;
+  size?: ButtonSize;
+}
+
+const variantStyles: Record<ButtonVariant, string> = {
+  primary: "bg-foreground text-background shadow-[var(--shadow-sm)] hover:bg-foreground/90 hover:shadow-[var(--shadow-lg)]",
+  secondary: "border-2 border-border/70 bg-surface text-foreground shadow-[var(--shadow-sm)] hover:bg-background hover:shadow-[var(--shadow-md)]",
+  ghost: "text-foreground hover:bg-border/30",
+  "unit-1": "bg-unit-1 text-white shadow-[var(--shadow-sm)] hover:bg-unit-1-dark hover:shadow-[var(--shadow-lg)]",
+  "unit-2": "bg-unit-2 text-white shadow-[var(--shadow-sm)] hover:bg-unit-2-dark hover:shadow-[var(--shadow-lg)]",
+  "unit-3": "bg-unit-3 text-white shadow-[var(--shadow-sm)] hover:bg-unit-3-dark hover:shadow-[var(--shadow-lg)]",
+  "unit-4": "bg-unit-4 text-white shadow-[var(--shadow-sm)] hover:bg-unit-4-dark hover:shadow-[var(--shadow-lg)]",
+};
+
+const sizeStyles: Record<ButtonSize, string> = {
+  sm: "px-4 py-2 text-sm",
+  md: "px-5.5 py-2.5 text-base",
+  lg: "px-8 py-3.5 text-lg",
+};
+
+export function Button({
+  variant = "primary",
+  size = "md",
+  className,
+  children,
+  ...props
+}: ButtonProps) {
+  return (
+    <button
+      className={cn(
+        "inline-flex items-center justify-center gap-2 rounded-2xl font-extrabold tracking-wide transition-all duration-200",
+        "active:translate-y-0.5",
+        "focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-unit-1",
+        "disabled:pointer-events-none disabled:opacity-50",
+        variantStyles[variant],
+        sizeStyles[size],
+        className,
+      )}
+      {...props}
+    >
+      {children}
+    </button>
+  );
+}

components/ui/card.tsx

@@ -0,0 +1,76 @@
+import { cn } from "@/lib/utils";
+import { type HTMLAttributes } from "react";
+
+interface CardProps extends HTMLAttributes<HTMLDivElement> {
+  accent?: "unit-1" | "unit-2" | "unit-3" | "unit-4";
+  hover?: boolean;
+}
+
+const accentStyles = {
+  "unit-1": "border-l-4 border-l-unit-1",
+  "unit-2": "border-l-4 border-l-unit-2",
+  "unit-3": "border-l-4 border-l-unit-3",
+  "unit-4": "border-l-4 border-l-unit-4",
+};
+
+export function Card({
+  accent,
+  hover = false,
+  className,
+  children,
+  ...props
+}: CardProps) {
+  return (
+    <div
+      className={cn(
+        "rounded-3xl border-2 border-border/60 bg-surface p-6",
+        "shadow-[var(--shadow-sm)]",
+        accent && accentStyles[accent],
+        hover && "transition-all duration-200 hover:-translate-y-1 hover:shadow-[var(--shadow-lg)]",
+        className,
+      )}
+      {...props}
+    >
+      {children}
+    </div>
+  );
+}
+
+export function CardHeader({
+  className,
+  children,
+  ...props
+}: HTMLAttributes<HTMLDivElement>) {
+  return (
+    <div className={cn("mb-4", className)} {...props}>
+      {children}
+    </div>
+  );
+}
+
+export function CardTitle({
+  className,
+  children,
+  ...props
+}: HTMLAttributes<HTMLHeadingElement>) {
+  return (
+    <h3
+      className={cn("text-xl font-bold tracking-tight", className)}
+      {...props}
+    >
+      {children}
+    </h3>
+  );
+}
+
+export function CardDescription({
+  className,
+  children,
+  ...props
+}: HTMLAttributes<HTMLParagraphElement>) {
+  return (
+    <p className={cn("text-sm text-muted", className)} {...props}>
+      {children}
+    </p>
+  );
+}

docker-compose.yml

@@ -0,0 +1,16 @@
+services:
+  cabrits:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    image: registry.dwarrington.com/cabrits:${IMAGE_TAG}
+    container_name: cabrits
+    restart: always
+    ports:
+      - "5030:3000"
+    networks:
+      - caddy_network
+
+networks:
+  caddy_network:
+    external: true

lib/curriculum.ts

@@ -0,0 +1,198 @@
+export interface Topic {
+  slug: string;
+  title: string;
+  shortTitle: string;
+  week: number;
+  description: string;
+}
+
+export interface Unit {
+  number: 1 | 2 | 3 | 4;
+  slug: string;
+  title: string;
+  description: string;
+  weeks: string;
+  color: "unit-1" | "unit-2" | "unit-3" | "unit-4";
+  topics: Topic[];
+}
+
+export const curriculum: Unit[] = [
+  {
+    number: 1,
+    slug: "unit-1-fractions",
+    title: "Fractions",
+    description: "Add, subtract, multiply, divide fractions and apply to quantities",
+    weeks: "Weeks 1-3",
+    color: "unit-1",
+    topics: [
+      {
+        slug: "add-subtract",
+        title: "Add and Subtract Fractions",
+        shortTitle: "Add & Subtract",
+        week: 1,
+        description: "Common and uncommon denominators, Butterfly Method",
+      },
+      {
+        slug: "multiply",
+        title: "Multiply Fractions",
+        shortTitle: "Multiply",
+        week: 1,
+        description: "Multiply numerators and denominators, simplify",
+      },
+      {
+        slug: "divide",
+        title: "Divide Fractions",
+        shortTitle: "Divide",
+        week: 1,
+        description: "Invert and multiply (reciprocal method)",
+      },
+      {
+        slug: "mixed-operations",
+        title: "Mixed Operations (BODMAS)",
+        shortTitle: "BODMAS",
+        week: 2,
+        description: "Order of operations with fractions",
+      },
+      {
+        slug: "fraction-of-quantity",
+        title: "Fraction of a Quantity",
+        shortTitle: "Of a Quantity",
+        week: 3,
+        description: "Calculate a fraction of a given amount",
+      },
+      {
+        slug: "whole-from-fractions",
+        title: "Calculate the Whole from Fractions",
+        shortTitle: "Find the Whole",
+        week: 3,
+        description: "Find the whole when given a part and its fraction",
+      },
+    ],
+  },
+  {
+    number: 2,
+    slug: "unit-2-decimals",
+    title: "Decimals",
+    description: "Compare, order, round decimals and express in standard form",
+    weeks: "Weeks 4-5",
+    color: "unit-2",
+    topics: [
+      {
+        slug: "compare-order",
+        title: "Compare and Order Decimals",
+        shortTitle: "Compare & Order",
+        week: 4,
+        description: "Place value, ascending, descending, greater/less than",
+      },
+      {
+        slug: "approximate",
+        title: "Approximate Decimals",
+        shortTitle: "Approximation",
+        week: 4,
+        description: "Round to whole numbers, decimal places, significant figures",
+      },
+      {
+        slug: "standard-form",
+        title: "Standard Form (Scientific Notation)",
+        shortTitle: "Standard Form",
+        week: 5,
+        description: "Express numbers as a × 10^n",
+      },
+    ],
+  },
+  {
+    number: 3,
+    slug: "unit-3-decimal-operations",
+    title: "Decimal Operations",
+    description: "Convert, add, subtract, multiply and divide decimals",
+    weeks: "Weeks 6-7",
+    color: "unit-3",
+    topics: [
+      {
+        slug: "convert",
+        title: "Convert Decimals and Fractions",
+        shortTitle: "Convert",
+        week: 6,
+        description: "Decimals to fractions and fractions to decimals",
+      },
+      {
+        slug: "add-subtract",
+        title: "Add and Subtract Decimals",
+        shortTitle: "Add & Subtract",
+        week: 6,
+        description: "Align decimal points, insert zeros as placeholders",
+      },
+      {
+        slug: "multiply-divide",
+        title: "Multiply and Divide Decimals",
+        shortTitle: "Multiply & Divide",
+        week: 7,
+        description: "By powers of 10, whole numbers, and decimals",
+      },
+    ],
+  },
+  {
+    number: 4,
+    slug: "unit-4-ratio-proportion",
+    title: "Ratio & Proportion",
+    description: "Define, simplify, and apply ratios to solve problems",
+    weeks: "Weeks 8-9",
+    color: "unit-4",
+    topics: [
+      {
+        slug: "define-ratio",
+        title: "Define a Ratio",
+        shortTitle: "Define Ratio",
+        week: 8,
+        description: "Relationship between two or more quantities",
+      },
+      {
+        slug: "fractions-and-ratios",
+        title: "Fractions and Ratios",
+        shortTitle: "Fractions & Ratios",
+        week: 8,
+        description: "Understand the relationship between fractions and ratios",
+      },
+      {
+        slug: "simplify-ratios",
+        title: "Simplify Ratios",
+        shortTitle: "Simplify",
+        week: 8,
+        description: "Write ratios in their simplest form",
+      },
+      {
+        slug: "divide-in-ratio",
+        title: "Divide a Quantity in a Given Ratio",
+        shortTitle: "Divide in Ratio",
+        week: 9,
+        description: "Share amounts using ratios",
+      },
+      {
+        slug: "word-problems",
+        title: "Proportional Parts Word Problems",
+        shortTitle: "Word Problems",
+        week: 9,
+        description: "Solve real-world problems with ratios",
+      },
+    ],
+  },
+];
+
+export function getUnit(slug: string): Unit | undefined {
+  return curriculum.find((u) => u.slug === slug);
+}
+
+export function getTopic(unitSlug: string, topicSlug: string): Topic | undefined {
+  const unit = getUnit(unitSlug);
+  return unit?.topics.find((t) => t.slug === topicSlug);
+}
+
+export function getUnitColor(unitNumber: 1 | 2 | 3 | 4): string {
+  const colors = {
+    1: "unit-1",
+    2: "unit-2",
+    3: "unit-3",
+    4: "unit-4",
+  };
+  return colors[unitNumber];
+}

lib/math/decimals.ts

@@ -0,0 +1,65 @@
+export function roundToWholeNumber(value: number): number {
+  return Math.round(value);
+}
+
+export function roundToDecimalPlaces(value: number, places: number): number {
+  const factor = Math.pow(10, places);
+  return Math.round(value * factor) / factor;
+}
+
+export function roundToSignificantFigures(value: number, sigFigs: number): number {
+  if (value === 0) return 0;
+  const magnitude = Math.floor(Math.log10(Math.abs(value)));
+  const factor = Math.pow(10, sigFigs - 1 - magnitude);
+  return Math.round(value * factor) / factor;
+}
+
+export function toStandardForm(value: number): { coefficient: number; exponent: number } {
+  if (value === 0) return { coefficient: 0, exponent: 0 };
+  const exponent = Math.floor(Math.log10(Math.abs(value)));
+  const coefficient = value / Math.pow(10, exponent);
+  return {
+    coefficient: roundToDecimalPlaces(coefficient, 10),
+    exponent,
+  };
+}
+
+export function fromStandardForm(coefficient: number, exponent: number): number {
+  return coefficient * Math.pow(10, exponent);
+}
+
+export function compareDecimals(a: number, b: number): -1 | 0 | 1 {
+  if (a > b) return 1;
+  if (a < b) return -1;
+  return 0;
+}
+
+export function getPlaceValue(value: number): { digit: number; place: string }[] {
+  const places = [
+    "thousands", "hundreds", "tens", "units", "tenths", "hundredths", "thousandths",
+  ];
+  const str = Math.abs(value).toFixed(3);
+  const [intPart, decPart] = str.split(".");
+  const paddedInt = intPart.padStart(4, "0");
+  const result: { digit: number; place: string }[] = [];
+
+  for (let i = 0; i < 4; i++) {
+    result.push({ digit: parseInt(paddedInt[i]), place: places[i] });
+  }
+  for (let i = 0; i < 3; i++) {
+    result.push({ digit: parseInt(decPart[i]), place: places[4 + i] });
+  }
+  return result;
+}
+
+export function multiplyByPowerOf10(value: number, power: number): number {
+  return roundToDecimalPlaces(value * Math.pow(10, power), 10);
+}
+
+export function divideByPowerOf10(value: number, power: number): number {
+  return roundToDecimalPlaces(value / Math.pow(10, power), 10);
+}
+
+export function standardFormToKatex(coefficient: number, exponent: number): string {
+  return `${coefficient} \\times 10^{${exponent}}`;
+}

lib/math/fractions.ts

@@ -0,0 +1,107 @@
+export function gcd(a: number, b: number): number {
+  a = Math.abs(a);
+  b = Math.abs(b);
+  while (b) {
+    [a, b] = [b, a % b];
+  }
+  return a;
+}
+
+export function lcm(a: number, b: number): number {
+  return Math.abs(a * b) / gcd(a, b);
+}
+
+export function simplify(num: number, den: number): [number, number] {
+  if (den === 0) return [num, den];
+  const g = gcd(Math.abs(num), Math.abs(den));
+  const sign = den < 0 ? -1 : 1;
+  return [(num / g) * sign, (den / g) * sign];
+}
+
+export function add(
+  n1: number, d1: number,
+  n2: number, d2: number,
+): [number, number] {
+  const num = n1 * d2 + n2 * d1;
+  const den = d1 * d2;
+  return simplify(num, den);
+}
+
+export function subtract(
+  n1: number, d1: number,
+  n2: number, d2: number,
+): [number, number] {
+  const num = n1 * d2 - n2 * d1;
+  const den = d1 * d2;
+  return simplify(num, den);
+}
+
+export function multiply(
+  n1: number, d1: number,
+  n2: number, d2: number,
+): [number, number] {
+  return simplify(n1 * n2, d1 * d2);
+}
+
+export function divide(
+  n1: number, d1: number,
+  n2: number, d2: number,
+): [number, number] {
+  return simplify(n1 * d2, d1 * n2);
+}
+
+export function toDecimal(num: number, den: number): number {
+  return num / den;
+}
+
+export function fromDecimal(decimal: number, precision: number = 6): [number, number] {
+  const str = decimal.toFixed(precision);
+  const parts = str.split(".");
+  if (!parts[1]) return [parseInt(parts[0]), 1];
+  const den = Math.pow(10, parts[1].length);
+  const num = Math.round(decimal * den);
+  return simplify(num, den);
+}
+
+export function compare(
+  n1: number, d1: number,
+  n2: number, d2: number,
+): -1 | 0 | 1 {
+  const diff = n1 * d2 - n2 * d1;
+  if (diff > 0) return 1;
+  if (diff < 0) return -1;
+  return 0;
+}
+
+export function fractionOfQuantity(num: number, den: number, quantity: number): number {
+  return (num / den) * quantity;
+}
+
+export function wholeFromFraction(num: number, den: number, part: number): number {
+  return (part * den) / num;
+}
+
+export function isProper(num: number, den: number): boolean {
+  return Math.abs(num) < Math.abs(den);
+}
+
+export function toMixed(num: number, den: number): [number, number, number] {
+  const whole = Math.floor(Math.abs(num) / Math.abs(den));
+  const remainder = Math.abs(num) % Math.abs(den);
+  const sign = (num < 0) !== (den < 0) ? -1 : 1;
+  return [whole * sign, remainder, Math.abs(den)];
+}
+
+export function fromMixed(whole: number, num: number, den: number): [number, number] {
+  const sign = whole < 0 ? -1 : 1;
+  return [sign * (Math.abs(whole) * den + num), den];
+}
+
+export function isSimplified(num: number, den: number): boolean {
+  return gcd(Math.abs(num), Math.abs(den)) === 1;
+}
+
+export function toKatex(num: number, den: number): string {
+  if (den === 1) return `${num}`;
+  return `\\frac{${num}}{${den}}`;
+}

lib/math/ratios.ts

@@ -0,0 +1,35 @@
+import { gcd } from "./fractions";
+
+export function simplifyRatio(parts: number[]): number[] {
+  if (parts.length === 0) return [];
+  let g = parts[0];
+  for (let i = 1; i < parts.length; i++) {
+    g = gcd(g, parts[i]);
+  }
+  return parts.map((p) => p / g);
+}
+
+export function divideInRatio(total: number, parts: number[]): number[] {
+  const sum = parts.reduce((a, b) => a + b, 0);
+  const onePart = total / sum;
+  return parts.map((p) => p * onePart);
+}
+
+export function ratioToFraction(a: number, b: number): [number, number] {
+  return [a, a + b];
+}
+
+export function areEquivalent(ratio1: number[], ratio2: number[]): boolean {
+  if (ratio1.length !== ratio2.length) return false;
+  const s1 = simplifyRatio(ratio1);
+  const s2 = simplifyRatio(ratio2);
+  return s1.every((v, i) => v === s2[i]);
+}
+
+export function totalParts(parts: number[]): number {
+  return parts.reduce((a, b) => a + b, 0);
+}
+
+export function ratioToKatex(parts: number[]): string {
+  return parts.join(":");
+}

lib/math/validation.ts

@@ -0,0 +1,94 @@
+import { gcd } from "./fractions";
+import { simplifyRatio } from "./ratios";
+
+export type AnswerResult =
+  | { correct: true; simplified: boolean }
+  | { correct: false; message: string };
+
+export function checkFractionAnswer(
+  userNum: number,
+  userDen: number,
+  expectedNum: number,
+  expectedDen: number,
+  requireSimplified: boolean = true,
+): AnswerResult {
+  if (userDen === 0) {
+    return { correct: false, message: "Denominator cannot be zero" };
+  }
+
+  // Check mathematical equivalence
+  const isEquivalent = userNum * expectedDen === expectedNum * userDen;
+
+  if (!isEquivalent) {
+    return { correct: false, message: "That's not quite right. Try again!" };
+  }
+
+  const isSimplified = gcd(Math.abs(userNum), Math.abs(userDen)) === 1;
+
+  if (requireSimplified && !isSimplified) {
+    return { correct: true, simplified: false };
+  }
+
+  return { correct: true, simplified: true };
+}
+
+export function checkDecimalAnswer(
+  userValue: number,
+  expectedValue: number,
+  tolerance: number = 0.001,
+): AnswerResult {
+  if (Math.abs(userValue - expectedValue) <= tolerance) {
+    return { correct: true, simplified: true };
+  }
+  return { correct: false, message: "That's not quite right. Try again!" };
+}
+
+export function checkRatioAnswer(
+  userParts: number[],
+  expectedParts: number[],
+  requireSimplified: boolean = true,
+): AnswerResult {
+  if (userParts.length !== expectedParts.length) {
+    return { correct: false, message: "Check the number of parts in your ratio" };
+  }
+
+  const userSimplified = simplifyRatio(userParts);
+  const expectedSimplified = simplifyRatio(expectedParts);
+
+  const isEquivalent = userSimplified.every((v, i) => v === expectedSimplified[i]);
+
+  if (!isEquivalent) {
+    return { correct: false, message: "That's not quite right. Try again!" };
+  }
+
+  if (requireSimplified) {
+    const isAlreadySimplified = userParts.every((v, i) => v === userSimplified[i]);
+    return { correct: true, simplified: isAlreadySimplified };
+  }
+
+  return { correct: true, simplified: true };
+}
+
+export function checkIntegerAnswer(
+  userValue: number,
+  expectedValue: number,
+): AnswerResult {
+  if (userValue === expectedValue) {
+    return { correct: true, simplified: true };
+  }
+  return { correct: false, message: "That's not quite right. Try again!" };
+}
+
+export function checkOrderingAnswer(
+  userOrder: number[],
+  expectedOrder: number[],
+): AnswerResult {
+  if (userOrder.length !== expectedOrder.length) {
+    return { correct: false, message: "Make sure you've ordered all the numbers" };
+  }
+  const isCorrect = userOrder.every((v, i) => v === expectedOrder[i]);
+  if (isCorrect) {
+    return { correct: true, simplified: true };
+  }
+  return { correct: false, message: "Check your ordering. Try again!" };
+}

lib/problems/generators/decimal-problems.ts

@@ -0,0 +1,287 @@
+import type { MathProblem, Difficulty } from "../types";
+import { randomInt, randomChoice, shuffle } from "@/lib/utils";
+import { roundToDecimalPlaces, roundToSignificantFigures, toStandardForm, standardFormToKatex } from "@/lib/math/decimals";
+
+let counter = 0;
+function nextId() {
+  return `dp-${++counter}-${Date.now()}`;
+}
+
+export function generateDecimalCompareOrder(difficulty: Difficulty): MathProblem {
+  const count = difficulty === 1 ? 3 : difficulty === 2 ? 4 : 5;
+  const values: number[] = [];
+
+  for (let i = 0; i < count; i++) {
+    const intPart = randomInt(0, difficulty === 1 ? 2 : 10);
+    const decPlaces = randomInt(1, difficulty === 1 ? 2 : 3);
+    const decPart = randomInt(1, Math.pow(10, decPlaces) - 1);
+    const val = intPart + decPart / Math.pow(10, decPlaces);
+    values.push(Math.round(val * 1000) / 1000);
+  }
+
+  const sorted = [...values].sort((a, b) => a - b);
+  const shuffled = shuffle(values);
+
+  return {
+    id: nextId(),
+    prompt: `\\text{Order from smallest to largest: } ${shuffled.join(", ")}`,
+    answer: { kind: "decimal", value: 0 },
+    hints: [
+      "Compare the whole number part first",
+      "If the whole parts are equal, compare tenths, then hundredths",
+      "Writing them with the same number of decimal places can help",
+    ],
+    steps: sorted.map((v, i) => ({
+      explanation: `Position ${i + 1}: ${v}`,
+    })),
+  };
+}
+
+export function generateDecimalRounding(difficulty: Difficulty): MathProblem {
+  const value = randomInt(100, 99999) / (difficulty === 1 ? 100 : 1000);
+  const roundType = randomChoice(
+    difficulty === 1
+      ? ["whole", "1dp"] as const
+      : difficulty === 2
+        ? ["1dp", "2dp", "whole"] as const
+        : ["1sf", "2sf", "3sf"] as const,
+  );
+
+  let answer: number;
+  let instruction: string;
+
+  switch (roundType) {
+    case "whole":
+      answer = Math.round(value);
+      instruction = "the nearest whole number";
+      break;
+    case "1dp":
+      answer = roundToDecimalPlaces(value, 1);
+      instruction = "1 decimal place";
+      break;
+    case "2dp":
+      answer = roundToDecimalPlaces(value, 2);
+      instruction = "2 decimal places";
+      break;
+    case "1sf":
+      answer = roundToSignificantFigures(value, 1);
+      instruction = "1 significant figure";
+      break;
+    case "2sf":
+      answer = roundToSignificantFigures(value, 2);
+      instruction = "2 significant figures";
+      break;
+    case "3sf":
+      answer = roundToSignificantFigures(value, 3);
+      instruction = "3 significant figures";
+      break;
+  }
+
+  return {
+    id: nextId(),
+    prompt: `\\text{Round } ${value} \\text{ to ${instruction}}`,
+    answer: { kind: "decimal", value: answer },
+    hints: [
+      "Look at the digit to the right of where you're rounding",
+      "If it's 5 or more, round up. If it's less than 5, round down",
+    ],
+    steps: [
+      { explanation: `Rounding ${value} to ${instruction}` },
+      { explanation: `Answer: ${answer}` },
+    ],
+  };
+}
+
+export function generateStandardForm(difficulty: Difficulty): MathProblem {
+  let value: number;
+  if (difficulty === 1) {
+    value = randomChoice([7438, 1578, 62, 93000, 5200, 340]);
+  } else if (difficulty === 2) {
+    value = randomChoice([0.086, 0.748, 0.0055, 0.34, 0.007]);
+  } else {
+    value = randomChoice([12436.3, 0.00092, 504000, 0.0000067, 83100]);
+  }
+
+  const sf = toStandardForm(value);
+
+  return {
+    id: nextId(),
+    prompt: `\\text{Express } ${value} \\text{ in standard form}`,
+    answer: { kind: "standardForm", coefficient: sf.coefficient, exponent: sf.exponent },
+    hints: [
+      "Move the decimal point so there's one non-zero digit before it",
+      "Count how many places you moved the decimal",
+      value >= 1
+        ? "Number is ≥ 1, so the power is positive"
+        : "Number is < 1, so the power is negative",
+    ],
+    steps: [
+      { explanation: `Move the decimal point to get a number between 1 and 10` },
+      { explanation: `Coefficient: ${sf.coefficient}` },
+      { explanation: `The decimal moved ${Math.abs(sf.exponent)} places, power = ${sf.exponent}` },
+      { explanation: "Answer", math: standardFormToKatex(sf.coefficient, sf.exponent) },
+    ],
+  };
+}
+
+export function generateDecimalAddSubtract(difficulty: Difficulty): MathProblem {
+  const operation = randomChoice(["add", "subtract"] as const);
+  const op = operation === "add" ? "+" : "-";
+  const places = difficulty === 1 ? 1 : difficulty === 2 ? 2 : 3;
+
+  const a = randomInt(100, 9999) / Math.pow(10, places);
+  const b = randomInt(100, 9999) / Math.pow(10, places);
+  const [first, second] = operation === "subtract" ? [Math.max(a, b), Math.min(a, b)] : [a, b];
+
+  const answer = roundToDecimalPlaces(
+    operation === "add" ? first + second : first - second,
+    places,
+  );
+
+  return {
+    id: nextId(),
+    prompt: `${first} ${op} ${second}`,
+    answer: { kind: "decimal", value: answer },
+    hints: [
+      "Line up the decimal points",
+      "Add zeros to fill empty places",
+      operation === "add" ? "Add column by column from right to left" : "Subtract column by column, borrow if needed",
+    ],
+    steps: [
+      { explanation: `Line up: ${first} ${op} ${second}` },
+      { explanation: `= ${answer}` },
+    ],
+  };
+}
+
+export function generateDecimalMultiplyDivide(difficulty: Difficulty): MathProblem {
+  const operation = randomChoice(["multiply", "divide"] as const);
+
+  if (difficulty === 1) {
+    // By powers of 10
+    const power = randomChoice([10, 100, 1000]);
+    const base = randomInt(1, 999) / 100;
+
+    if (operation === "multiply") {
+      const answer = roundToDecimalPlaces(base * power, 10);
+      return {
+        id: nextId(),
+        prompt: `${base} \\times ${power}`,
+        answer: { kind: "decimal", value: answer },
+        hints: [
+          `When multiplying by ${power}, move decimal ${Math.log10(power)} place(s) right`,
+        ],
+        steps: [
+          { explanation: `Move decimal point ${Math.log10(power)} place(s) to the right` },
+          { explanation: `= ${answer}` },
+        ],
+      };
+    } else {
+      const answer = roundToDecimalPlaces(base / power, 10);
+      return {
+        id: nextId(),
+        prompt: `${base} \\div ${power}`,
+        answer: { kind: "decimal", value: answer },
+        hints: [
+          `When dividing by ${power}, move decimal ${Math.log10(power)} place(s) left`,
+        ],
+        steps: [
+          { explanation: `Move decimal point ${Math.log10(power)} place(s) to the left` },
+          { explanation: `= ${answer}` },
+        ],
+      };
+    }
+  }
+
+  // By whole numbers or decimals
+  const a = randomInt(10, 999) / 10;
+  const b = difficulty === 2 ? randomInt(2, 12) : randomInt(10, 99) / 10;
+
+  if (operation === "multiply") {
+    const answer = roundToDecimalPlaces(a * b, 4);
+    return {
+      id: nextId(),
+      prompt: `${a} \\times ${b}`,
+      answer: { kind: "decimal", value: answer },
+      hints: [
+        "Multiply as if there are no decimal points",
+        "Count total decimal places in both numbers",
+        "Place the decimal point in your answer",
+      ],
+      steps: [
+        { explanation: `${a} × ${b}` },
+        { explanation: `= ${answer}` },
+      ],
+    };
+  } else {
+    const answer = roundToDecimalPlaces(a / b, 4);
+    return {
+      id: nextId(),
+      prompt: `${a} \\div ${b}`,
+      answer: { kind: "decimal", value: answer },
+      hints: [
+        "Place decimal point in answer directly above the one in the dividend",
+        "Divide as normal",
+      ],
+      steps: [
+        { explanation: `${a} ÷ ${b}` },
+        { explanation: `= ${answer}` },
+      ],
+    };
+  }
+}
+
+export function generateDecimalConversion(difficulty: Difficulty): MathProblem {
+  const direction = randomChoice(["toFraction", "toDecimal"] as const);
+
+  if (direction === "toFraction") {
+    const decimal = randomChoice(
+      difficulty === 1
+        ? [0.5, 0.25, 0.75, 0.1, 0.2, 0.4]
+        : [0.125, 0.375, 0.625, 0.875, 0.15, 0.35, 0.45],
+    );
+    const den = decimal === 0.5 ? 2 : decimal === 0.25 || decimal === 0.75 ? 4 : [0.125, 0.375, 0.625, 0.875].includes(decimal) ? 8 : 100;
+    const num = Math.round(decimal * den);
+    const g = gcdSimple(num, den);
+
+    return {
+      id: nextId(),
+      prompt: `\\text{Convert } ${decimal} \\text{ to a fraction}`,
+      answer: { kind: "fraction", numerator: num / g, denominator: den / g },
+      hints: [
+        `Write as ${num}/${den}`,
+        "Simplify by dividing numerator and denominator by their GCD",
+      ],
+      steps: [
+        { explanation: `${decimal} = ${num}/${den}` },
+        { explanation: `Simplified: ${num / g}/${den / g}` },
+      ],
+    };
+  } else {
+    const den = randomChoice(difficulty === 1 ? [2, 4, 5, 10] : [3, 8, 20, 25, 40, 50]);
+    const num = randomInt(1, den - 1);
+    const answer = roundToDecimalPlaces(num / den, 6);
+
+    return {
+      id: nextId(),
+      prompt: `\\text{Convert } \\frac{${num}}{${den}} \\text{ to a decimal}`,
+      answer: { kind: "decimal", value: answer },
+      hints: [
+        `Divide ${num} by ${den}`,
+        "Or find an equivalent fraction with denominator 10, 100, etc.",
+      ],
+      steps: [
+        { explanation: `${num} ÷ ${den} = ${answer}` },
+      ],
+    };
+  }
+}
+
+function gcdSimple(a: number, b: number): number {
+  a = Math.abs(a);
+  b = Math.abs(b);
+  while (b) {
+    [a, b] = [b, a % b];
+  }
+  return a;
+}

lib/problems/generators/fraction-problems.ts

@@ -0,0 +1,163 @@
+import type { MathProblem, Difficulty } from "../types";
+import { randomInt, randomChoice } from "@/lib/utils";
+import * as frac from "@/lib/math/fractions";
+
+let counter = 0;
+function nextId() {
+  return `fp-${++counter}-${Date.now()}`;
+}
+
+export function generateFractionAddSubtract(difficulty: Difficulty): MathProblem {
+  const operation = randomChoice(["add", "subtract"] as const);
+  const op = operation === "add" ? "+" : "-";
+
+  let n1: number, d1: number, n2: number, d2: number;
+
+  if (difficulty === 1) {
+    // Common denominators
+    d1 = randomChoice([2, 3, 4, 5, 6, 8, 10, 12]);
+    d2 = d1;
+    n1 = randomInt(1, d1 - 1);
+    n2 = operation === "subtract" ? randomInt(1, n1) : randomInt(1, d1 - n1);
+  } else if (difficulty === 2) {
+    // One denominator is a multiple of the other
+    d1 = randomChoice([2, 3, 4, 5, 6]);
+    const multiplier = randomChoice([2, 3]);
+    d2 = d1 * multiplier;
+    n1 = randomInt(1, d1 - 1);
+    n2 = randomInt(1, d2 - 1);
+  } else {
+    // Unlike denominators
+    d1 = randomChoice([3, 4, 5, 7, 8, 9]);
+    d2 = randomChoice([3, 4, 5, 7, 8, 9].filter((d) => d !== d1));
+    n1 = randomInt(1, d1 - 1);
+    n2 = randomInt(1, d2 - 1);
+  }
+
+  const [ansNum, ansDen] = operation === "add"
+    ? frac.add(n1, d1, n2, d2)
+    : frac.subtract(n1, d1, n2, d2);
+
+  const prompt = `\\frac{${n1}}{${d1}} ${op} \\frac{${n2}}{${d2}}`;
+
+  const commonDen = frac.lcm(d1, d2);
+  const steps = d1 === d2
+    ? [
+        { explanation: "Denominators are the same, so just " + (operation === "add" ? "add" : "subtract") + " the numerators" },
+        { explanation: `${n1} ${op} ${n2} = ${operation === "add" ? n1 + n2 : n1 - n2}`, math: `\\frac{${operation === "add" ? n1 + n2 : n1 - n2}}{${d1}}` },
+      ]
+    : [
+        { explanation: `Find the common denominator: LCM(${d1}, ${d2}) = ${commonDen}` },
+        { explanation: `Convert: ${n1}×${commonDen / d1}/${d1}×${commonDen / d1} and ${n2}×${commonDen / d2}/${d2}×${commonDen / d2}` },
+        { explanation: `${op === "+" ? "Add" : "Subtract"} numerators`, math: `\\frac{${ansNum}}{${ansDen}}` },
+      ];
+
+  return {
+    id: nextId(),
+    prompt,
+    answer: { kind: "fraction", numerator: ansNum, denominator: ansDen },
+    hints: [
+      d1 === d2 ? "The denominators are already the same!" : "Find a common denominator first",
+      d1 !== d2 ? `Try using the Butterfly Method: cross multiply` : `Just ${operation} the numerators`,
+    ],
+    steps,
+  };
+}
+
+export function generateFractionMultiply(difficulty: Difficulty): MathProblem {
+  const denChoices = difficulty === 1 ? [2, 3, 4, 5] : difficulty === 2 ? [2, 3, 4, 5, 6, 7, 8] : [3, 5, 7, 9, 11, 12, 15];
+  const d1 = randomChoice(denChoices);
+  const d2 = randomChoice(denChoices);
+  const n1 = randomInt(1, d1 - 1);
+  const n2 = randomInt(1, d2 - 1);
+
+  const [ansNum, ansDen] = frac.multiply(n1, d1, n2, d2);
+
+  return {
+    id: nextId(),
+    prompt: `\\frac{${n1}}{${d1}} \\times \\frac{${n2}}{${d2}}`,
+    answer: { kind: "fraction", numerator: ansNum, denominator: ansDen },
+    hints: [
+      "Multiply numerator × numerator",
+      "Multiply denominator × denominator",
+      "Simplify if possible",
+    ],
+    steps: [
+      { explanation: `Multiply numerators: ${n1} × ${n2} = ${n1 * n2}` },
+      { explanation: `Multiply denominators: ${d1} × ${d2} = ${d1 * d2}` },
+      { explanation: "Simplify", math: `\\frac{${ansNum}}{${ansDen}}` },
+    ],
+  };
+}
+
+export function generateFractionDivide(difficulty: Difficulty): MathProblem {
+  const denChoices = difficulty === 1 ? [2, 3, 4, 5] : difficulty === 2 ? [2, 3, 4, 5, 6, 7, 8] : [3, 5, 7, 9, 11, 14, 15];
+  const d1 = randomChoice(denChoices);
+  const d2 = randomChoice(denChoices);
+  const n1 = randomInt(1, d1 - 1);
+  const n2 = randomInt(1, d2 - 1);
+
+  const [ansNum, ansDen] = frac.divide(n1, d1, n2, d2);
+
+  return {
+    id: nextId(),
+    prompt: `\\frac{${n1}}{${d1}} \\div \\frac{${n2}}{${d2}}`,
+    answer: { kind: "fraction", numerator: ansNum, denominator: ansDen },
+    hints: [
+      "Keep the first fraction the same",
+      "Flip the second fraction (reciprocal)",
+      "Then multiply",
+    ],
+    steps: [
+      { explanation: `Keep ${n1}/${d1}, flip ${n2}/${d2} to ${d2}/${n2}` },
+      { explanation: `Multiply: ${n1}×${d2} / ${d1}×${n2}` },
+      { explanation: "Simplify", math: `\\frac{${ansNum}}{${ansDen}}` },
+    ],
+  };
+}
+
+export function generateFractionOfQuantity(difficulty: Difficulty): MathProblem {
+  const denChoices = difficulty === 1 ? [2, 4, 5, 10] : difficulty === 2 ? [3, 4, 5, 6, 8] : [7, 8, 9, 12, 15];
+  const den = randomChoice(denChoices);
+  const num = randomInt(1, den - 1);
+  const multiplier = randomChoice(difficulty === 1 ? [2, 4, 5, 10] : [3, 6, 7, 8, 9, 12]);
+  const quantity = den * multiplier;
+  const answer = num * multiplier;
+
+  return {
+    id: nextId(),
+    prompt: `\\frac{${num}}{${den}} \\text{ of } ${quantity}`,
+    answer: { kind: "integer", value: answer },
+    hints: [
+      `Divide ${quantity} by ${den} first`,
+      `Then multiply by ${num}`,
+    ],
+    steps: [
+      { explanation: `Divide the quantity by the denominator: ${quantity} ÷ ${den} = ${quantity / den}` },
+      { explanation: `Multiply by the numerator: ${quantity / den} × ${num} = ${answer}` },
+    ],
+  };
+}
+
+export function generateWholeFromFraction(difficulty: Difficulty): MathProblem {
+  const denChoices = difficulty === 1 ? [2, 3, 4, 5] : difficulty === 2 ? [3, 5, 6, 8] : [7, 8, 9, 12];
+  const den = randomChoice(denChoices);
+  const num = randomInt(1, den - 1);
+  const whole = den * randomChoice(difficulty === 1 ? [2, 3, 4, 5] : [3, 5, 6, 7, 8, 10]);
+  const part = (num / den) * whole;
+
+  return {
+    id: nextId(),
+    prompt: `\\frac{${num}}{${den}} \\text{ of a number is } ${part}\\text{. Find the number.}`,
+    answer: { kind: "integer", value: whole },
+    hints: [
+      `If ${num}/${den} of the number is ${part}...`,
+      `Find 1/${den} first by dividing ${part} by ${num}`,
+      `Then multiply by ${den} to get the whole`,
+    ],
+    steps: [
+      { explanation: `1/${den} of the number = ${part} ÷ ${num} = ${part / num}` },
+      { explanation: `The whole number = ${part / num} × ${den} = ${whole}` },
+    ],
+  };
+}

lib/problems/generators/ratio-problems.ts

@@ -0,0 +1,110 @@
+import type { MathProblem, Difficulty } from "../types";
+import { randomInt, randomChoice } from "@/lib/utils";
+import { simplifyRatio, divideInRatio } from "@/lib/math/ratios";
+
+let counter = 0;
+function nextId() {
+  return `rp-${++counter}-${Date.now()}`;
+}
+
+export function generateSimplifyRatio(difficulty: Difficulty): MathProblem {
+  const gcd = randomChoice(difficulty === 1 ? [2, 3, 4, 5] : difficulty === 2 ? [3, 4, 5, 6, 7] : [4, 6, 8, 9, 12]);
+  const a = randomInt(1, difficulty === 1 ? 5 : 10) * gcd;
+  const b = randomInt(1, difficulty === 1 ? 5 : 10) * gcd;
+
+  const simplified = simplifyRatio([a, b]);
+
+  return {
+    id: nextId(),
+    prompt: `\\text{Simplify the ratio } ${a}:${b}`,
+    answer: { kind: "ratio", parts: simplified },
+    hints: [
+      `Find the GCD of ${a} and ${b}`,
+      `The GCD is ${gcd}`,
+      `Divide both parts by ${gcd}`,
+    ],
+    steps: [
+      { explanation: `GCD of ${a} and ${b} is ${gcd}` },
+      { explanation: `${a} ÷ ${gcd} = ${simplified[0]}, ${b} ÷ ${gcd} = ${simplified[1]}` },
+      { explanation: `Simplified: ${simplified.join(":")}` },
+    ],
+  };
+}
+
+export function generateDivideInRatio(difficulty: Difficulty): MathProblem {
+  const numParts = difficulty === 3 ? 3 : 2;
+  const parts: number[] = [];
+  for (let i = 0; i < numParts; i++) {
+    parts.push(randomInt(1, difficulty === 1 ? 5 : 9));
+  }
+
+  const sum = parts.reduce((a, b) => a + b, 0);
+  const multiplier = randomChoice(difficulty === 1 ? [2, 3, 4, 5] : [3, 4, 5, 6, 7, 8]);
+  const total = sum * multiplier;
+
+  const values = divideInRatio(total, parts);
+  const intValues = values.map(Math.round);
+
+  const names = ["first share", "second share", "third share"];
+
+  return {
+    id: nextId(),
+    prompt: `\\text{Share } ${total} \\text{ in the ratio } ${parts.join(":")}`,
+    answer: { kind: "ratio", parts: intValues },
+    hints: [
+      `Total parts: ${parts.join(" + ")} = ${sum}`,
+      `One part = ${total} ÷ ${sum} = ${multiplier}`,
+      `Multiply each ratio number by ${multiplier}`,
+    ],
+    steps: [
+      { explanation: `Total parts = ${parts.join(" + ")} = ${sum}` },
+      { explanation: `One part = ${total} ÷ ${sum} = ${multiplier}` },
+      ...parts.map((p, i) => ({
+        explanation: `${names[i]}: ${p} × ${multiplier} = ${intValues[i]}`,
+      })),
+    ],
+  };
+}
+
+export function generateRatioWordProblem(difficulty: Difficulty): MathProblem {
+  const a = randomInt(2, 7);
+  const b = randomInt(2, 7);
+  const diff = Math.abs(a - b);
+
+  if (diff === 0) {
+    return generateDivideInRatio(difficulty);
+  }
+
+  const contexts = [
+    { item: "sweets", nameA: "Josh", nameB: "Nathan" },
+    { item: "marbles", nameA: "Amy", nameB: "Ben" },
+    { item: "stickers", nameA: "Karen", nameB: "Natasha" },
+  ];
+  const ctx = randomChoice(contexts);
+
+  const onePart = randomChoice(difficulty === 1 ? [5, 10, 12] : [6, 8, 9, 15, 20]);
+  const extraAmount = diff * onePart;
+  const totalParts = a + b;
+  const total = totalParts * onePart;
+
+  const bigger = a > b ? ctx.nameA : ctx.nameB;
+  const biggerRatio = Math.max(a, b);
+  const smallerRatio = Math.min(a, b);
+
+  return {
+    id: nextId(),
+    prompt: `\\text{${ctx.item.charAt(0).toUpperCase() + ctx.item.slice(1)} were shared between ${ctx.nameA} and ${ctx.nameB} in the ratio ${a}:${b}. If ${bigger} received ${extraAmount} more ${ctx.item}, find the total shared.}`,
+    answer: { kind: "integer", value: total },
+    hints: [
+      `The difference in ratio parts is ${biggerRatio} - ${smallerRatio} = ${diff}`,
+      `${diff} parts = ${extraAmount}, so 1 part = ${onePart}`,
+      `Total parts = ${a} + ${b} = ${totalParts}`,
+    ],
+    steps: [
+      { explanation: `Difference in parts: ${biggerRatio} - ${smallerRatio} = ${diff}` },
+      { explanation: `${diff} parts = ${extraAmount}, so 1 part = ${extraAmount} ÷ ${diff} = ${onePart}` },
+      { explanation: `Total parts: ${a} + ${b} = ${totalParts}` },
+      { explanation: `Total ${ctx.item}: ${totalParts} × ${onePart} = ${total}` },
+    ],
+  };
+}

lib/problems/types.ts

@@ -0,0 +1,21 @@
+export type Difficulty = 1 | 2 | 3;
+
+export type MathAnswer =
+  | { kind: "fraction"; numerator: number; denominator: number }
+  | { kind: "decimal"; value: number }
+  | { kind: "integer"; value: number }
+  | { kind: "ratio"; parts: number[] }
+  | { kind: "standardForm"; coefficient: number; exponent: number };
+
+export interface SolutionStep {
+  explanation: string;
+  math?: string;
+}
+
+export interface MathProblem {
+  id: string;
+  prompt: string;
+  answer: MathAnswer;
+  hints: string[];
+  steps: SolutionStep[];
+}

lib/utils.ts

@@ -0,0 +1,23 @@
+import { clsx, type ClassValue } from "clsx";
+import { twMerge } from "tailwind-merge";
+
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs));
+}
+
+export function randomInt(min: number, max: number): number {
+  return Math.floor(Math.random() * (max - min + 1)) + min;
+}
+
+export function randomChoice<T>(arr: T[]): T {
+  return arr[Math.floor(Math.random() * arr.length)];
+}
+
+export function shuffle<T>(arr: T[]): T[] {
+  const result = [...arr];
+  for (let i = result.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1));
+    [result[i], result[j]] = [result[j], result[i]];
+  }
+  return result;
+}

next.config.ts

@@ -1,7 +1,7 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  /* config options here */
+  output: "standalone",
 };
 
 export default nextConfig;

package-lock.json

@@ -8,12 +8,17 @@
       "name": "cabrits",
       "version": "0.1.0",
       "dependencies": {
+        "clsx": "^2.1.1",
+        "framer-motion": "^12.34.3",
+        "katex": "^0.16.33",
         "next": "16.1.6",
         "react": "19.2.3",
-        "react-dom": "19.2.3"
+        "react-dom": "19.2.3",
+        "tailwind-merge": "^3.5.0"
       },
       "devDependencies": {
         "@tailwindcss/postcss": "^4",
+        "@types/katex": "^0.16.8",
         "@types/node": "^20",
         "@types/react": "^19",
         "@types/react-dom": "^19",
@@ -1445,6 +1450,12 @@
       "integrity": "sha512-dRLjCWHYg4oaA77cxO64oO+7JwCwnIzkZPdrrC71jQmQtlhM556pwKo5bUzqvZndkVbeFLIIi+9TC40JNF5hNQ==",
       "dev": true
     },
+    "node_modules/@types/katex": {
+      "version": "0.16.8",
+      "resolved": "https://registry.npmjs.org/@types/katex/-/katex-0.16.8.tgz",
+      "integrity": "sha512-trgaNyfU+Xh2Tc+ABIb44a5AYUpicB3uwirOioeOkNPPbmgRNtcWyDeeFRzjPZENO9Vq8gvVqfhaaXWLlevVwg==",
+      "dev": true
+    },
     "node_modules/@types/node": {
       "version": "20.19.35",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-20.19.35.tgz",
@@ -2436,6 +2447,14 @@
       "resolved": "https://registry.npmjs.org/client-only/-/client-only-0.0.1.tgz",
       "integrity": "sha512-IV3Ou0jSMzZrd3pZ48nLkT9DA7Ag1pnPzaiQhpW7c3RbcqqzvzzVu+L8gfqMp/8IM2MQtSiqaCxrrcfu8I8rMA=="
     },
+    "node_modules/clsx": {
+      "version": "2.1.1",
+      "resolved": "https://registry.npmjs.org/clsx/-/clsx-2.1.1.tgz",
+      "integrity": "sha512-eYm0QWBtUrBWZWG0d386OGAw16Z995PiOVo2B7bjWSbHedGl5e0ZWaq65kOGgUSNesEIDkB9ISbTg/JK9dhCZA==",
+      "engines": {
+        "node": ">=6"
+      }
+    },
     "node_modules/color-convert": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/color-convert/-/color-convert-2.0.1.tgz",
@@ -2454,6 +2473,14 @@
       "integrity": "sha512-dOy+3AuW3a2wNbZHIuMZpTcgjGuLU/uBL/ubcZF9OXbDo8ff4O8yVp5Bf0efS8uEoYo5q4Fx7dY9OgQGXgAsQA==",
       "dev": true
     },
+    "node_modules/commander": {
+      "version": "8.3.0",
+      "resolved": "https://registry.npmjs.org/commander/-/commander-8.3.0.tgz",
+      "integrity": "sha512-OkTL9umf+He2DZkUq8f8J9of7yL6RJKI24dVITBmNfZBmri9zYZQrKkuXiKhyfPSu8tUhnVBB1iKXevvnlR4Ww==",
+      "engines": {
+        "node": ">= 12"
+      }
+    },
     "node_modules/concat-map": {
       "version": "0.0.1",
       "resolved": "https://registry.npmjs.org/concat-map/-/concat-map-0.0.1.tgz",
@@ -3388,6 +3415,32 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/framer-motion": {
+      "version": "12.34.3",
+      "resolved": "https://registry.npmjs.org/framer-motion/-/framer-motion-12.34.3.tgz",
+      "integrity": "sha512-v81ecyZKYO/DfpTwHivqkxSUBzvceOpoI+wLfgCgoUIKxlFKEXdg0oR9imxwXumT4SFy8vRk9xzJ5l3/Du/55Q==",
+      "dependencies": {
+        "motion-dom": "^12.34.3",
+        "motion-utils": "^12.29.2",
+        "tslib": "^2.4.0"
+      },
+      "peerDependencies": {
+        "@emotion/is-prop-valid": "*",
+        "react": "^18.0.0 || ^19.0.0",
+        "react-dom": "^18.0.0 || ^19.0.0"
+      },
+      "peerDependenciesMeta": {
+        "@emotion/is-prop-valid": {
+          "optional": true
+        },
+        "react": {
+          "optional": true
+        },
+        "react-dom": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/function-bind": {
       "version": "1.1.2",
       "resolved": "https://registry.npmjs.org/function-bind/-/function-bind-1.1.2.tgz",
@@ -4219,6 +4272,21 @@
         "node": ">=4.0"
       }
     },
+    "node_modules/katex": {
+      "version": "0.16.33",
+      "resolved": "https://registry.npmjs.org/katex/-/katex-0.16.33.tgz",
+      "integrity": "sha512-q3N5u+1sY9Bu7T4nlXoiRBXWfwSefNGoKeOwekV+gw0cAXQlz2Ww6BLcmBxVDeXBMUDQv6fK5bcNaJLxob3ZQA==",
+      "funding": [
+        "https://opencollective.com/katex",
+        "https://github.com/sponsors/katex"
+      ],
+      "dependencies": {
+        "commander": "^8.3.0"
+      },
+      "bin": {
+        "katex": "cli.js"
+      }
+    },
     "node_modules/keyv": {
       "version": "4.5.4",
       "resolved": "https://registry.npmjs.org/keyv/-/keyv-4.5.4.tgz",
@@ -4611,6 +4679,19 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/motion-dom": {
+      "version": "12.34.3",
+      "resolved": "https://registry.npmjs.org/motion-dom/-/motion-dom-12.34.3.tgz",
+      "integrity": "sha512-sYgFe+pR9aIM7o4fhs2aXtOI+oqlUd33N9Yoxcgo1Fv7M20sRkHtCmzE/VRNIcq7uNJ+qio+Xubt1FXH3pQ+eQ==",
+      "dependencies": {
+        "motion-utils": "^12.29.2"
+      }
+    },
+    "node_modules/motion-utils": {
+      "version": "12.29.2",
+      "resolved": "https://registry.npmjs.org/motion-utils/-/motion-utils-12.29.2.tgz",
+      "integrity": "sha512-G3kc34H2cX2gI63RqU+cZq+zWRRPSsNIOjpdl9TN4AQwC4sgwYPl/Q/Obf/d53nOm569T0fYK+tcoSV50BWx8A=="
+    },
     "node_modules/ms": {
       "version": "2.1.3",
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
@@ -5676,6 +5757,15 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/tailwind-merge": {
+      "version": "3.5.0",
+      "resolved": "https://registry.npmjs.org/tailwind-merge/-/tailwind-merge-3.5.0.tgz",
+      "integrity": "sha512-I8K9wewnVDkL1NTGoqWmVEIlUcB9gFriAEkXkfCjX5ib8ezGxtR3xD7iZIxrfArjEsH7F1CHD4RFUtxefdqV/A==",
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/dcastil"
+      }
+    },
     "node_modules/tailwindcss": {
       "version": "4.2.1",
       "resolved": "https://registry.npmjs.org/tailwindcss/-/tailwindcss-4.2.1.tgz",

package.json

@@ -9,12 +9,17 @@
     "lint": "eslint"
   },
   "dependencies": {
+    "clsx": "^2.1.1",
+    "framer-motion": "^12.34.3",
+    "katex": "^0.16.33",
     "next": "16.1.6",
     "react": "19.2.3",
-    "react-dom": "19.2.3"
+    "react-dom": "19.2.3",
+    "tailwind-merge": "^3.5.0"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@types/katex": "^0.16.8",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",

standard-form-explorer.html

@@ -0,0 +1,836 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Standard Form Explorer</title>
+    <style>
+        :root {
+            --primary:   #1a237e;
+            --secondary: #3f51b5;
+            --accent:    #e91e63;
+            --orange:    #ff6f00;
+            --green:     #2e7d32;
+            --digit-w:   68px;
+            --digit-h:   88px;
+            --digit-gap: 10px;
+            --dot-size:  18px;
+        }
+
+        * { box-sizing: border-box; margin: 0; padding: 0; }
+
+        body {
+            font-family: 'Segoe UI', Tahoma, sans-serif;
+            background: #f0f2f8;
+            min-height: 100vh;
+            display: flex;
+            flex-direction: column;
+        }
+
+        /* ── HEADER ───────────────────────────────────── */
+        header {
+            background: var(--primary);
+            color: white;
+            padding: 14px 28px;
+            display: flex;
+            align-items: center;
+            justify-content: space-between;
+            flex-wrap: wrap;
+            gap: 10px;
+        }
+        header h1 { font-size: 1.4rem; letter-spacing: .3px; }
+
+        .mode-tabs { display: flex; gap: 8px; }
+        .tab {
+            background: rgba(255,255,255,.15);
+            border: 2px solid rgba(255,255,255,.4);
+            color: white;
+            padding: 8px 18px;
+            border-radius: 20px;
+            cursor: pointer;
+            font-size: .9rem;
+            font-family: inherit;
+            transition: all .2s;
+        }
+        .tab.active { background: white; color: var(--primary); border-color: white; font-weight: 700; }
+        .tab:hover:not(.active) { background: rgba(255,255,255,.25); }
+
+        /* ── MAIN ─────────────────────────────────────── */
+        main {
+            flex: 1;
+            max-width: 900px;
+            width: 100%;
+            margin: 0 auto;
+            padding: 20px 20px 32px;
+            display: flex;
+            flex-direction: column;
+            gap: 14px;
+        }
+
+        .card {
+            background: white;
+            border-radius: 12px;
+            padding: 18px 24px;
+            box-shadow: 0 2px 10px rgba(0,0,0,.09);
+        }
+
+        /* ── INPUT ────────────────────────────────────── */
+        .input-heading {
+            font-size: .78rem;
+            font-weight: 700;
+            text-transform: uppercase;
+            letter-spacing: .7px;
+            color: var(--secondary);
+            margin-bottom: 12px;
+        }
+        .input-row {
+            display: flex;
+            align-items: center;
+            flex-wrap: wrap;
+            gap: 10px;
+        }
+        .input-row input {
+            font-size: 1.25rem;
+            padding: 10px 14px;
+            border: 2px solid #c5cae9;
+            border-radius: 8px;
+            outline: none;
+            font-family: inherit;
+            transition: border-color .2s;
+        }
+        .input-row input:focus { border-color: var(--secondary); }
+        #ordinary-input  { max-width: 220px; }
+        #coeff-input     { max-width: 140px; }
+        #power-input     { max-width: 110px; }
+
+        .input-row label { font-size: 1.15rem; font-weight: 600; color: var(--primary); }
+
+        .btn-go {
+            background: var(--secondary);
+            color: white;
+            border: none;
+            padding: 11px 26px;
+            border-radius: 8px;
+            font-size: 1rem;
+            font-weight: 700;
+            cursor: pointer;
+            font-family: inherit;
+            transition: background .2s;
+        }
+        .btn-go:hover { background: var(--primary); }
+
+        .error-msg { color: #e53935; font-size: .92rem; margin-top: 8px; }
+        .hidden { display: none !important; }
+
+        /* ── DISPLAY ──────────────────────────────────── */
+        #display-card {
+            min-height: 260px;
+            display: flex;
+            flex-direction: column;
+            align-items: center;
+            justify-content: center;
+            gap: 10px;
+            padding: 24px;
+        }
+
+        #placeholder {
+            color: #bdbdbd;
+            font-size: 1.15rem;
+            text-align: center;
+        }
+
+        #step-info {
+            font-size: .88rem;
+            color: #9e9e9e;
+            min-height: 20px;
+            letter-spacing: .2px;
+        }
+
+        /* Digit row */
+        #number-row {
+            position: relative;
+            display: inline-flex;
+            align-items: flex-end;
+            gap: var(--digit-gap);
+            padding: 8px 16px 28px 16px;
+        }
+
+        .digit-box {
+            width:  var(--digit-w);
+            height: var(--digit-h);
+            display: flex;
+            align-items: center;
+            justify-content: center;
+            font-size: 3.2rem;
+            font-weight: 700;
+            color: var(--primary);
+            background: var(--light);
+            border: 2px solid #c5cae9;
+            border-radius: 10px;
+            flex-shrink: 0;
+            transition: background .35s, border-color .35s, color .35s;
+            user-select: none;
+        }
+
+        .digit-box.dim {
+            color: #c0c0c0;
+            background: #f5f5f5;
+            border-color: #e0e0e0;
+        }
+
+        .digit-box.highlight {
+            background: #e3f2fd;
+            border-color: var(--secondary);
+            color: var(--primary);
+        }
+
+        /* Decimal dot */
+        #decimal-dot {
+            position: absolute;
+            bottom: 7px;
+            width:  var(--dot-size);
+            height: var(--dot-size);
+            background: var(--accent);
+            border-radius: 50%;
+            transform: translateX(-50%);
+            transition: left .52s cubic-bezier(.34,1.56,.64,1), opacity .3s;
+            box-shadow: 0 2px 8px rgba(233,30,99,.45);
+            z-index: 5;
+        }
+        #decimal-dot.no-anim { transition: none; }
+
+        /* Direction label */
+        #direction-label {
+            font-size: .95rem;
+            font-weight: 600;
+            min-height: 22px;
+        }
+        .dir-left  { color: var(--accent); }
+        .dir-right { color: var(--orange); }
+        .dir-done  { color: var(--green); }
+
+        /* Power counter */
+        #power-row {
+            display: flex;
+            align-items: baseline;
+            gap: 5px;
+            font-size: 1.7rem;
+            color: #616161;
+        }
+        #power-row .base  { font-weight: 700; color: var(--primary); }
+        #power-row sup    { font-size: 2rem; font-weight: 800; color: var(--orange);
+                            min-width: 38px; display: inline-block; }
+        #power-val { transition: all .15s; display: inline-block; }
+        #power-val.pop { animation: pop .28s ease; }
+        @keyframes pop {
+            0%  { transform: scale(.5); }
+            65% { transform: scale(1.35); }
+            100%{ transform: scale(1); }
+        }
+
+        /* ── CONTROLS ─────────────────────────────────── */
+        #controls {
+            display: flex;
+            align-items: center;
+            justify-content: center;
+            flex-wrap: wrap;
+            gap: 10px;
+            padding: 14px 20px;
+        }
+
+        .ctrl {
+            padding: 12px 22px;
+            border: 2px solid;
+            border-radius: 9px;
+            font-size: 1rem;
+            font-weight: 700;
+            cursor: pointer;
+            font-family: inherit;
+            transition: all .15s;
+        }
+        .ctrl:disabled { opacity: .35; cursor: not-allowed; }
+
+        #btn-back  { background: white; border-color: var(--secondary); color: var(--secondary); }
+        #btn-back:hover:not(:disabled)  { background: var(--secondary); color: white; }
+
+        #btn-play  { background: var(--green); border-color: var(--green); color: white; min-width: 115px; }
+        #btn-play:hover:not(:disabled)  { background: #1b5e20; border-color: #1b5e20; }
+
+        #btn-step  { background: var(--secondary); border-color: var(--secondary); color: white;
+                     font-size: 1.05rem; padding: 12px 28px; }
+        #btn-step:hover:not(:disabled)  { background: var(--primary); border-color: var(--primary); }
+
+        #btn-reset { background: white; border-color: #e53935; color: #e53935; }
+        #btn-reset:hover:not(:disabled) { background: #e53935; color: white; }
+
+        /* ── RESULT ───────────────────────────────────── */
+        #result-card {
+            text-align: center;
+            min-height: 90px;
+            display: flex;
+            flex-direction: column;
+            align-items: center;
+            justify-content: center;
+            gap: 6px;
+        }
+        #result-label { font-size: .82rem; color: #9e9e9e; text-transform: uppercase; letter-spacing: .5px; }
+        #result-value { font-size: 2.6rem; font-weight: 800; }
+        #result-value .r-coeff { color: var(--primary); }
+        #result-value .r-times { color: #616161; margin: 0 8px; }
+        #result-value .r-base  { color: var(--primary); }
+        #result-value .r-exp   { color: var(--accent); font-size: 1.9rem; }
+        #result-placeholder { color: #c5c5c5; font-size: 1rem; }
+
+        /* ── KEYBOARD HINT ────────────────────────────── */
+        #kb-hint {
+            text-align: center;
+            font-size: .78rem;
+            color: #b0b0b0;
+            padding: 4px 0 0;
+        }
+        #kb-hint kbd {
+            background: #ececec;
+            border: 1px solid #ccc;
+            border-radius: 4px;
+            padding: 1px 5px;
+            font-size: .75rem;
+            font-family: monospace;
+        }
+
+        /* ── RESPONSIVE ───────────────────────────────── */
+        @media (max-width: 580px) {
+            :root { --digit-w: 52px; --digit-h: 70px; --digit-gap: 6px; }
+            .digit-box { font-size: 2.4rem; }
+            #result-value { font-size: 1.9rem; }
+        }
+    </style>
+</head>
+<body>
+
+<!-- ═══════════════════════════════════════════════ HEADER -->
+<header>
+    <h1>🔢 Standard Form Explorer</h1>
+    <div class="mode-tabs">
+        <button class="tab active" id="tab-sf"  onclick="setMode('toSF')">Ordinary → Standard Form</button>
+        <button class="tab"        id="tab-ord" onclick="setMode('toOrd')">Standard Form → Ordinary</button>
+    </div>
+</header>
+
+<!-- ═══════════════════════════════════════════════ MAIN -->
+<main>
+
+    <!-- INPUT: Ordinary → Standard Form -->
+    <div class="card" id="panel-sf">
+        <div class="input-heading">Enter an ordinary number</div>
+        <div class="input-row">
+            <input type="text" id="ordinary-input"
+                   placeholder="e.g. 7438 or 0.0055"
+                   maxlength="18" autocomplete="off">
+            <button class="btn-go" onclick="convertToSF()">Convert →</button>
+        </div>
+        <div class="error-msg hidden" id="err-sf"></div>
+    </div>
+
+    <!-- INPUT: Standard Form → Ordinary -->
+    <div class="card hidden" id="panel-ord">
+        <div class="input-heading">Enter a number in standard form &nbsp;A × 10<sup>n</sup></div>
+        <div class="input-row">
+            <input type="text"   id="coeff-input" placeholder="A  e.g. 3.6" maxlength="12" autocomplete="off">
+            <label>× 10<sup>n</sup> &nbsp; where n =</label>
+            <input type="number" id="power-input" placeholder="e.g. 4 or −3" autocomplete="off">
+            <button class="btn-go" onclick="convertToOrd()">Convert →</button>
+        </div>
+        <div class="error-msg hidden" id="err-ord"></div>
+    </div>
+
+    <!-- DISPLAY -->
+    <div class="card" id="display-card">
+        <div id="placeholder">Enter a number above and click <strong>Convert</strong></div>
+
+        <div id="step-info" class="hidden"></div>
+
+        <div id="number-row" class="hidden">
+            <div id="decimal-dot"></div>
+        </div>
+
+        <div id="direction-label" class="hidden"></div>
+
+        <div id="power-row" class="hidden">
+            <span>×</span>
+            <span class="base">10</span>
+            <sup><span id="power-val">0</span></sup>
+        </div>
+    </div>
+
+    <!-- CONTROLS -->
+    <div class="card" id="controls">
+        <button class="ctrl" id="btn-back"  onclick="stepBack()"    disabled>◀ Back</button>
+        <button class="ctrl" id="btn-play"  onclick="togglePlay()"  disabled>▶ Play</button>
+        <button class="ctrl" id="btn-step"  onclick="stepForward()" disabled>Next Step ▶</button>
+        <button class="ctrl" id="btn-reset" onclick="resetAll()"    disabled>↺ Reset</button>
+    </div>
+
+    <!-- RESULT -->
+    <div class="card" id="result-card">
+        <div id="result-placeholder">Result will appear here when steps are complete</div>
+        <div id="result-label"  class="hidden"></div>
+        <div id="result-value"  class="hidden"></div>
+    </div>
+
+    <!-- KEYBOARD HINT -->
+    <div id="kb-hint">
+        Keyboard: <kbd>Space</kbd> or <kbd>→</kbd> next step &nbsp;·&nbsp;
+        <kbd>←</kbd> back &nbsp;·&nbsp; <kbd>P</kbd> play/pause &nbsp;·&nbsp; <kbd>R</kbd> reset
+    </div>
+
+</main>
+
+<!-- ═══════════════════════════════════════════════ SCRIPT -->
+<script>
+'use strict';
+
+// ─── STATE ────────────────────────────────────────────────────────────────────
+const S = {
+    mode:          'toSF',   // 'toSF' | 'toOrd'
+    digits:        [],       // char array, e.g. ['7','4','3','8']
+    decimalPos:    0,        // current position of decimal point
+    initPos:       0,        // starting position (reset target)
+    targetPos:     0,        // where we want to get to
+    origPower:     0,        // original power stored for toOrd mode
+    ready:         false,
+    done:          false,
+    playing:       false,
+    timer:         null,
+};
+
+// ─── MODE SWITCH ──────────────────────────────────────────────────────────────
+function setMode(m) {
+    S.mode = m;
+    show('panel-sf',  m === 'toSF');
+    show('panel-ord', m === 'toOrd');
+    id('tab-sf') .classList.toggle('active', m === 'toSF');
+    id('tab-ord').classList.toggle('active', m === 'toOrd');
+    resetAll();
+}
+
+// ─── HELPERS ──────────────────────────────────────────────────────────────────
+const id   = s => document.getElementById(s);
+const show = (el, vis) => id(el).classList.toggle('hidden', !vis);
+
+function setErr(panelId, msg) {
+    const el = id(panelId);
+    el.textContent = msg;
+    el.classList.toggle('hidden', !msg);
+}
+
+// ─── PARSING ──────────────────────────────────────────────────────────────────
+/**
+ * Parse an ordinary-form string into { digits, decimalPos }.
+ * decimalPos = number of digits before the decimal point.
+ *   "7438"   → digits=['7','4','3','8'], decimalPos=4
+ *   "0.0055" → digits=['0','0','0','5','5'], decimalPos=1
+ *   "15.78"  → digits=['1','5','7','8'], decimalPos=2
+ */
+function parseOrdinary(raw) {
+    let s = raw.trim().replace(/[\s,]/g, '');
+    if (s.startsWith('-')) throw new Error('Please enter a positive number.');
+    if (!/^\d*\.?\d+$/.test(s) || s === '') throw new Error('Invalid number. Try something like 7438 or 0.0055');
+    if (s.length > 16) throw new Error('Number too long (max 16 digits).');
+
+    let dot = s.indexOf('.');
+    let digits, decimalPos;
+    if (dot === -1) {
+        digits     = s.split('');
+        decimalPos = s.length;
+    } else {
+        digits     = (s.slice(0, dot) + s.slice(dot + 1)).split('');
+        decimalPos = dot;
+    }
+    if (digits.length === 0) throw new Error('Invalid number.');
+    return { digits, decimalPos };
+}
+
+/** Index of the first non-zero digit, or -1 if all zeros. */
+function firstNonZero(digits) {
+    return digits.findIndex(d => d !== '0');
+}
+
+/** Target decimal position for standard form: just after first non-zero digit. */
+function sfTargetPos(digits) {
+    const i = firstNonZero(digits);
+    return i === -1 ? 1 : i + 1;
+}
+
+/** Current power based on mode and current decimalPos. */
+function currentPower() {
+    if (S.mode === 'toSF') {
+        return S.initPos - S.decimalPos;          // increases as decimal moves left
+    } else {
+        return S.origPower - (S.decimalPos - S.initPos); // decreases toward 0
+    }
+}
+
+// ─── CONVERT BUTTONS ──────────────────────────────────────────────────────────
+function convertToSF() {
+    setErr('err-sf', '');
+    try {
+        let { digits, decimalPos } = parseOrdinary(id('ordinary-input').value);
+        let target = sfTargetPos(digits);
+        S.origPower = 0; // not used in toSF
+        initDisplay(digits, decimalPos, target);
+    } catch(e) { setErr('err-sf', e.message); }
+}
+
+function convertToOrd() {
+    setErr('err-ord', '');
+    try {
+        let coeffRaw = id('coeff-input').value.trim();
+        let n        = parseInt(id('power-input').value, 10);
+
+        if (!coeffRaw) throw new Error('Enter the coefficient A.');
+        if (isNaN(n))  throw new Error('Enter the power n as a whole number.');
+        if (Math.abs(n) > 12) throw new Error('Power too large for display (max ±12).');
+        if (n === 0) throw new Error('Power is 0 — the number is already in ordinary form.');
+
+        let { digits, decimalPos } = parseOrdinary(coeffRaw);
+
+        // Validate 1 ≤ A < 10
+        let A = parseFloat(coeffRaw);
+        if (isNaN(A) || A < 1 || A >= 10)
+            throw new Error(`Coefficient must satisfy 1 ≤ A < 10 (got ${coeffRaw}).`);
+
+        // decimalPos for a valid coefficient is always 1
+        decimalPos = 1;
+
+        let expandedDigits = [...digits];
+        let startPos, targetPos;
+
+        if (n > 0) {
+            // Move decimal RIGHT n steps — need trailing zeros
+            targetPos = decimalPos + n;            // = 1 + n
+            startPos  = decimalPos;                // = 1
+            while (expandedDigits.length < targetPos) expandedDigits.push('0');
+        } else {
+            // Move decimal LEFT |n| steps — need leading zeros
+            let absN = Math.abs(n);
+            let zeros = Array(absN).fill('0');
+            expandedDigits = zeros.concat(expandedDigits);
+            startPos  = decimalPos + absN;         // = 1 + |n|  (decimal is now deeper in)
+            targetPos = startPos + n;              // = 1 + |n| + n = 1 (for n negative)
+        }
+
+        S.origPower = n;
+        initDisplay(expandedDigits, startPos, targetPos);
+    } catch(e) { setErr('err-ord', e.message); }
+}
+
+// ─── INITIALISE DISPLAY ───────────────────────────────────────────────────────
+function initDisplay(digits, start, target) {
+    stopPlay();
+
+    S.digits     = digits;
+    S.decimalPos = start;
+    S.initPos    = start;
+    S.targetPos  = target;
+    S.ready      = true;
+    S.done       = (start === target);
+
+    // Show display elements
+    show('placeholder',     false);
+    show('step-info',       true);
+    show('number-row',      true);
+    show('direction-label', true);
+    show('power-row',       true);
+
+    // Render
+    renderDigits();
+    refreshPower(false);
+    refreshDirection();
+    refreshStepInfo();
+    refreshButtons();
+    id('decimal-dot').style.opacity = '1';
+
+    // Clear result
+    show('result-placeholder', true);
+    show('result-label', false);
+    show('result-value', false);
+
+    // Position dot instantly (after DOM paints)
+    requestAnimationFrame(() => {
+        requestAnimationFrame(() => {
+            placeDot(false);
+            refreshDigitColors();
+            if (S.done) revealResult();
+        });
+    });
+}
+
+// ─── RENDERING ────────────────────────────────────────────────────────────────
+function renderDigits() {
+    const row = id('number-row');
+    row.querySelectorAll('.digit-box').forEach(el => el.remove());
+    S.digits.forEach((ch, i) => {
+        const box = document.createElement('div');
+        box.className = 'digit-box';
+        box.id = `db-${i}`;
+        box.textContent = ch;
+        row.insertBefore(box, id('decimal-dot'));
+    });
+}
+
+function refreshDigitColors() {
+    const fz = firstNonZero(S.digits);
+    S.digits.forEach((_, i) => {
+        const box = id(`db-${i}`);
+        if (!box) return;
+        box.className = 'digit-box';
+        if (i < fz) box.classList.add('dim');           // leading zeros
+        else if (i === S.targetPos - 1) box.classList.add('highlight'); // coefficient lead digit
+    });
+}
+
+function placeDot(animate = true) {
+    const row  = id('number-row');
+    const dot  = id('decimal-dot');
+    const boxes = row.querySelectorAll('.digit-box');
+    if (!boxes.length) return;
+
+    let leftPx;
+    const dp = S.decimalPos;
+
+    if (dp <= 0) {
+        leftPx = boxes[0].offsetLeft - 6;
+    } else if (dp >= boxes.length) {
+        const last = boxes[boxes.length - 1];
+        leftPx = last.offsetLeft + last.offsetWidth - 4;
+    } else {
+        const prev = boxes[dp - 1];
+        const next = boxes[dp];
+        leftPx = Math.round((prev.offsetLeft + prev.offsetWidth + next.offsetLeft) / 2);
+    }
+
+    if (!animate) {
+        dot.classList.add('no-anim');
+        dot.style.left = leftPx + 'px';
+        // Re-enable transitions after reflow
+        requestAnimationFrame(() => requestAnimationFrame(() => dot.classList.remove('no-anim')));
+    } else {
+        dot.style.left = leftPx + 'px';
+    }
+
+    // Hide dot if it's sitting at trailing end and we are done
+    dot.style.opacity = (S.done && dp >= boxes.length) ? '0' : '1';
+}
+
+function refreshPower(animate = true) {
+    const p  = currentPower();
+    const el = id('power-val');
+    el.textContent = p;
+    if (animate) {
+        el.classList.remove('pop');
+        void el.offsetWidth; // reflow
+        el.classList.add('pop');
+    }
+}
+
+function refreshDirection() {
+    const el  = id('direction-label');
+    const rem = S.targetPos - S.decimalPos;
+    if (!S.ready || S.done || rem === 0) {
+        el.textContent = '';
+        el.className = '';
+        return;
+    }
+    if (rem < 0) {
+        el.innerHTML = `← Moving <strong>left</strong> &nbsp;·&nbsp; ${Math.abs(rem)} step${Math.abs(rem)!==1?'s':''} remaining`;
+        el.className = 'dir-left';
+    } else {
+        el.innerHTML = `→ Moving <strong>right</strong> &nbsp;·&nbsp; ${rem} step${rem!==1?'s':''} remaining`;
+        el.className = 'dir-right';
+    }
+}
+
+function refreshStepInfo() {
+    const el    = id('step-info');
+    const total = Math.abs(S.targetPos - S.initPos);
+    const done  = Math.abs(S.decimalPos - S.initPos);
+    if (total === 0) {
+        el.textContent = 'Number is already in standard form position — power = 0';
+    } else {
+        el.textContent = `Step ${done} of ${total}`;
+    }
+}
+
+function refreshButtons() {
+    const atStart  = S.decimalPos === S.initPos;
+    const atTarget = S.decimalPos === S.targetPos;
+    id('btn-back') .disabled = !S.ready || atStart;
+    id('btn-step') .disabled = !S.ready || atTarget;
+    id('btn-play') .disabled = !S.ready || atTarget;
+    id('btn-reset').disabled = !S.ready;
+}
+
+// ─── STEPPING ─────────────────────────────────────────────────────────────────
+function stepForward() {
+    if (!S.ready || S.decimalPos === S.targetPos) return;
+    const dir = S.targetPos > S.initPos ? 1 : -1;
+    S.decimalPos += dir;
+
+    placeDot(true);
+    refreshPower(true);
+    refreshDigitColors();
+    refreshDirection();
+    refreshStepInfo();
+
+    if (S.decimalPos === S.targetPos) {
+        S.done = true;
+        stopPlay();
+        // Wait for dot transition to settle before showing result
+        setTimeout(revealResult, 560);
+        setTimeout(() => placeDot(false), 580); // update opacity if trailing
+    }
+    refreshButtons();
+}
+
+function stepBack() {
+    if (!S.ready || S.decimalPos === S.initPos) return;
+    if (S.done) {
+        S.done = false;
+        id('decimal-dot').style.opacity = '1';
+        show('result-placeholder', true);
+        show('result-label', false);
+        show('result-value', false);
+    }
+    const dir = S.targetPos > S.initPos ? -1 : 1;
+    S.decimalPos += dir;
+
+    placeDot(true);
+    refreshPower(true);
+    refreshDigitColors();
+    refreshDirection();
+    refreshStepInfo();
+    refreshButtons();
+}
+
+// ─── AUTO-PLAY ────────────────────────────────────────────────────────────────
+function togglePlay() {
+    S.playing ? stopPlay() : startPlay();
+}
+function startPlay() {
+    if (!S.ready || S.done) return;
+    S.playing = true;
+    id('btn-play').textContent = '⏸ Pause';
+    id('btn-step').disabled = true;
+    id('btn-back').disabled = true;
+    S.timer = setInterval(() => {
+        stepForward();
+        if (S.done) stopPlay();
+    }, 950);
+}
+function stopPlay() {
+    S.playing = false;
+    clearInterval(S.timer);
+    S.timer = null;
+    id('btn-play').textContent = '▶ Play';
+    refreshButtons();
+}
+
+// ─── RESET ────────────────────────────────────────────────────────────────────
+function resetAll() {
+    stopPlay();
+    S.ready = S.done = false;
+    show('placeholder',     true);
+    show('step-info',       false);
+    show('number-row',      false);
+    show('direction-label', false);
+    show('power-row',       false);
+    show('result-placeholder', true);
+    show('result-label', false);
+    show('result-value', false);
+    id('number-row').querySelectorAll('.digit-box').forEach(el => el.remove());
+    id('decimal-dot').style.opacity = '1';
+    id('power-val').textContent = '0';
+    id('step-info').textContent = '';
+    id('direction-label').textContent = '';
+    ['btn-back','btn-play','btn-step','btn-reset'].forEach(b => id(b).disabled = true);
+    id('btn-play').textContent = '▶ Play';
+}
+
+// ─── RESULT ───────────────────────────────────────────────────────────────────
+function revealResult() {
+    if (S.mode === 'toSF') {
+        const fz      = firstNonZero(S.digits);
+        const sigDigs = S.digits.slice(fz === -1 ? 0 : fz);
+        const power   = S.initPos - S.targetPos;
+        const coeff   = buildCoeff(sigDigs);
+
+        id('result-label').textContent = 'Standard Form';
+        id('result-value').innerHTML =
+            `<span class="r-coeff">${coeff}</span>` +
+            `<span class="r-times">×</span>` +
+            `<span class="r-base">10</span>` +
+            `<sup class="r-exp">${power}</sup>`;
+    } else {
+        const ord   = buildOrdinary(S.digits, S.targetPos);
+        const power = S.origPower;
+        const fz    = firstNonZero(S.digits);
+        const sig   = S.digits.slice(fz === -1 ? 0 : fz);
+        const coeff = buildCoeff(sig);
+
+        id('result-label').textContent = 'Ordinary Form';
+        id('result-value').innerHTML =
+            `<span class="r-coeff">${ord}</span>`;
+    }
+
+    show('result-placeholder', false);
+    show('result-label', true);
+    show('result-value', true);
+
+    // Animate result card briefly
+    const rc = id('result-card');
+    rc.style.transition = 'box-shadow .3s';
+    rc.style.boxShadow  = `0 0 0 4px ${getComputedStyle(document.documentElement)
+        .getPropertyValue('--green').trim()}`;
+    setTimeout(() => rc.style.boxShadow = '', 1200);
+}
+
+/** Build coefficient string: "7.438", "5.5", "1.0" */
+function buildCoeff(sigDigs) {
+    if (sigDigs.length === 0) return '0';
+    if (sigDigs.length === 1) return sigDigs[0] + '.0';
+    const rest = sigDigs.slice(1).join('').replace(/0+$/, '') || '0';
+    return sigDigs[0] + '.' + rest;
+}
+
+/** Build ordinary number string from digits + decimal position. */
+function buildOrdinary(digits, pos) {
+    let s;
+    if (pos <= 0) {
+        s = '0.' + '0'.repeat(-pos) + digits.join('');
+    } else if (pos >= digits.length) {
+        s = digits.join('') + '0'.repeat(pos - digits.length);
+    } else {
+        s = digits.slice(0, pos).join('') + '.' + digits.slice(pos).join('');
+    }
+    // Trim leading zeros (keep one before decimal)
+    s = s.replace(/^0+(?=[1-9])/, '');
+    if (s.startsWith('.')) s = '0' + s;
+    // Trim trailing zeros after decimal
+    if (s.includes('.')) s = s.replace(/\.?0+$/, '');
+    return s || '0';
+}
+
+// ─── KEYBOARD ─────────────────────────────────────────────────────────────────
+document.addEventListener('keydown', e => {
+    if (['INPUT','TEXTAREA','SELECT'].includes(e.target.tagName)) return;
+    if (e.key === 'ArrowRight' || e.key === ' ')  { e.preventDefault(); stepForward(); }
+    if (e.key === 'ArrowLeft')                    { e.preventDefault(); stepBack();    }
+    if (e.key.toLowerCase() === 'p')              togglePlay();
+    if (e.key.toLowerCase() === 'r')              resetAll();
+});
+id('ordinary-input').addEventListener('keydown', e => { if(e.key==='Enter') convertToSF(); });
+id('coeff-input')   .addEventListener('keydown', e => { if(e.key==='Enter') convertToOrd(); });
+id('power-input')   .addEventListener('keydown', e => { if(e.key==='Enter') convertToOrd(); });
+</script>
+</body>
+</html>