denary to binary

.claude/settings.local.json

@@ -1,7 +1,12 @@
 {
   "permissions": {
     "allow": [
-      "Bash(cd \"C:/Users/earl_/source/repos/CabritsMath/cabrits-math\" && npx next build 2>&1 | tail -80)"
+      "Bash(cd \"C:/Users/earl_/source/repos/CabritsMath/cabrits-math\" && npx next build 2>&1 | tail -80)",
+      "Bash(npx tsc *)",
+      "Bash(echo \"TSC_EXIT=$?\")",
+      "Bash(npx eslint *)",
+      "Bash(echo \"LINT_EXIT=$?\")",
+      "Bash(npx next *)"
     ]
   }
 }

app/lessons/unit-6-number-system/binary/page.tsx

@@ -1,9 +1,20 @@
 "use client";
 
+import { useState } from "react";
 import { Breadcrumbs } from "@/components/layout/breadcrumbs";
 import { BinaryConverterExplorer } from "@/components/explorers/binary-converter-explorer";
+import { DenaryToBinaryExplorer } from "@/components/explorers/denary-to-binary-explorer";
+
+type Mode = "binary-to-denary" | "denary-to-binary";
+
+const MODES: { key: Mode; label: string }[] = [
+  { key: "binary-to-denary", label: "Binary → Denary" },
+  { key: "denary-to-binary", label: "Denary → Binary" },
+];
 
 export default function BinaryPage() {
+  const [mode, setMode] = useState<Mode>("binary-to-denary");
+
   return (
     <div className="space-y-8">
       <Breadcrumbs
@@ -15,11 +26,39 @@ export default function BinaryPage() {
       />
 
       <div>
-        <h1 className="text-3xl font-bold tracking-tight">Binary &rarr; Decimal Converter</h1>
+        <h1 className="text-3xl font-bold tracking-tight">
-        <p className="mt-2 text-muted">Same shape, different base &mdash; explore place value in powers of 2.</p>
+          {mode === "binary-to-denary"
+            ? "Binary → Denary Converter"
+            : "Denary → Binary Converter"}
+        </h1>
+        <p className="mt-2 text-muted">
+          {mode === "binary-to-denary"
+            ? "Same shape, different base — explore place value in powers of 2."
+            : "Divide by 2. Track the remainder. Read bottom-up."}
+        </p>
       </div>
 
+      <div className="flex flex-wrap gap-2">
+        {MODES.map((m) => (
+          <button
+            key={m.key}
+            onClick={() => setMode(m.key)}
+            className={`rounded-full border-2 px-4 py-2 text-sm font-semibold transition-colors ${
+              mode === m.key
+                ? "border-unit-6 bg-unit-6 text-white"
+                : "border-unit-6/40 text-unit-6 hover:bg-unit-6-light"
+            }`}
+          >
+            {m.label}
+          </button>
+        ))}
+      </div>
+
+      {mode === "binary-to-denary" ? (
         <BinaryConverterExplorer />
+      ) : (
+        <DenaryToBinaryExplorer />
+      )}
     </div>
   );
 }

components/explorers/denary-to-binary-explorer.tsx

@@ -0,0 +1,368 @@
+"use client";
+
+import { useState, useMemo, useCallback } from "react";
+import { Card } from "@/components/ui/card";
+
+const COLUMNS = [32, 16, 8, 4, 2, 1];
+const PRESETS = [3, 5, 11, 13, 22, 25, 29, 31, 45, 58];
+
+interface DivisionRow {
+  before: number;
+  quotient: number;
+  remainder: number;
+}
+
+interface ConversionResult {
+  rows: DivisionRow[];
+  bitsLowToHigh: number[];
+}
+
+function runDivision(n: number): ConversionResult {
+  const rows: DivisionRow[] = [];
+  if (n === 0) {
+    rows.push({ before: 0, quotient: 0, remainder: 0 });
+    return { rows, bitsLowToHigh: [0] };
+  }
+  let current = n;
+  while (current > 0) {
+    const q = Math.floor(current / 2);
+    const r = current % 2;
+    rows.push({ before: current, quotient: q, remainder: r });
+    current = q;
+  }
+  return { rows, bitsLowToHigh: rows.map((r) => r.remainder) };
+}
+
+function bitsForChart(bitsLowToHigh: number[]): (number | null)[] {
+  const out: (number | null)[] = Array(COLUMNS.length).fill(null);
+  for (let i = 0; i < bitsLowToHigh.length && i < COLUMNS.length; i++) {
+    out[COLUMNS.length - 1 - i] = bitsLowToHigh[i];
+  }
+  return out;
+}
+
+export function DenaryToBinaryExplorer() {
+  const [input, setInput] = useState("");
+  const [submitted, setSubmitted] = useState<number | null>(null);
+  const [error, setError] = useState("");
+  const [answerHidden, setAnswerHidden] = useState(false);
+  const [chartHidden, setChartHidden] = useState(false);
+
+  const handleInputChange = (value: string) => {
+    setInput(value.replace(/[^0-9]/g, "").slice(0, 3));
+    setError("");
+  };
+
+  const convert = useCallback((raw?: string) => {
+    const source = (raw ?? input).trim();
+    if (source === "") {
+      setError("Type a denary number first (whole number from 1 to 63).");
+      setSubmitted(null);
+      return;
+    }
+    if (!/^\d+$/.test(source)) {
+      setError("Use whole digits only (0-9).");
+      return;
+    }
+    const n = parseInt(source, 10);
+    if (n < 0 || n > 63) {
+      setError("Pick a whole number between 1 and 63. The chart in this lesson is six columns: 32, 16, 8, 4, 2, 1.");
+      return;
+    }
+    setError("");
+    setSubmitted(n);
+  }, [input]);
+
+  const applyPreset = (value: number) => {
+    setInput(String(value));
+    convert(String(value));
+  };
+
+  const handleClear = () => {
+    setInput("");
+    setSubmitted(null);
+    setError("");
+  };
+
+  const handleRandom = () => {
+    const n = 1 + Math.floor(Math.random() * 63);
+    setInput(String(n));
+    convert(String(n));
+  };
+
+  const result = useMemo(() => {
+    if (submitted === null) return null;
+    return runDivision(submitted);
+  }, [submitted]);
+
+  const chartBits = useMemo(() => {
+    if (!result) return Array(COLUMNS.length).fill(null) as (number | null)[];
+    return bitsForChart(result.bitsLowToHigh);
+  }, [result]);
+
+  const binaryString = useMemo(() => {
+    if (!result) return "";
+    const reversed = result.bitsLowToHigh.slice().reverse().join("");
+    return reversed.replace(/^0+/, "") || "0";
+  }, [result]);
+
+  return (
+    <div className="space-y-4">
+      {/* Input Card */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-6">
+          Type a Denary Number (1 to 63)
+        </p>
+        <div className="flex flex-wrap items-center gap-3">
+          <label htmlFor="denaryInput" className="text-sm font-bold text-unit-6-dark">
+            Denary:
+          </label>
+          <input
+            id="denaryInput"
+            type="text"
+            inputMode="numeric"
+            maxLength={3}
+            autoComplete="off"
+            spellCheck={false}
+            placeholder="e.g. 13"
+            value={input}
+            onChange={(e) => handleInputChange(e.target.value)}
+            onKeyDown={(e) => {
+              if (e.key === "Enter") convert();
+            }}
+            className="w-32 rounded-lg border-2 border-unit-6 bg-surface px-3 py-2 text-center font-mono text-2xl font-bold tracking-[0.3em] text-unit-6 outline-none focus:border-unit-6-dark"
+            aria-label="Denary number input"
+          />
+          <button
+            onClick={() => convert()}
+            className="rounded-lg bg-unit-6 px-5 py-2.5 text-sm font-bold text-white transition-colors hover:bg-unit-6-dark"
+          >
+            Convert
+          </button>
+          <button
+            onClick={handleClear}
+            className="rounded-lg border-2 border-border bg-surface px-4 py-2 text-sm font-bold text-muted transition-colors hover:border-unit-6/50 hover:text-unit-6"
+          >
+            Clear
+          </button>
+          <button
+            onClick={handleRandom}
+            className="rounded-lg border-2 border-border bg-surface px-4 py-2 text-sm font-bold text-muted transition-colors hover:border-unit-6/50 hover:text-unit-6"
+          >
+            Random
+          </button>
+        </div>
+
+        <div className="mt-4 flex flex-wrap gap-2">
+          {PRESETS.map((p) => (
+            <button
+              key={p}
+              onClick={() => applyPreset(p)}
+              className="rounded-lg border-2 border-unit-6/30 bg-unit-6-light px-3 py-1 font-mono text-sm font-bold text-unit-6-dark transition-colors hover:border-unit-6 hover:bg-unit-6 hover:text-white"
+            >
+              {p}
+            </button>
+          ))}
+        </div>
+
+        {error && (
+          <p className="mt-3 rounded-lg border-2 border-incorrect bg-incorrect-light px-3 py-2 text-center text-sm font-bold text-incorrect">
+            {error}
+          </p>
+        )}
+      </Card>
+
+      {/* Division steps */}
+      <Card>
+        <p className="mb-3 text-xs font-bold uppercase tracking-wider text-unit-6">
+          Repeated Division by 2
+        </p>
+
+        <div className="rounded-xl border-2 border-hint/40 bg-hint-light/50 p-4">
+          {!result ? (
+            <p className="text-center font-mono text-sm text-muted">
+              Type a denary number above and press Convert to see the division table.
+            </p>
+          ) : submitted === 0 ? (
+            <p className="text-center font-mono text-base font-bold text-unit-6">
+              0 in binary is 0.
+            </p>
+          ) : (
+            <div className="overflow-x-auto">
+              <table className="mx-auto min-w-[380px] border-collapse font-mono text-sm">
+                <thead>
+                  <tr>
+                    {["Step", "n ÷ 2", "Quotient", "Remainder", ""].map((h, i) => (
+                      <th
+                        key={i}
+                        className={
+                          i === 4
+                            ? "px-3 py-2 text-left"
+                            : "border-2 border-unit-6/40 bg-unit-6-light px-4 py-2 text-xs font-bold uppercase tracking-wide text-unit-6-dark"
+                        }
+                      >
+                        {h}
+                      </th>
+                    ))}
+                  </tr>
+                </thead>
+                <tbody>
+                  {result.rows.map((row, idx) => (
+                    <tr key={idx}>
+                      <td className="border-2 border-unit-6/40 bg-surface px-4 py-2 text-center font-bold text-unit-6">
+                        {idx + 1}
+                      </td>
+                      <td className="border-2 border-unit-6/40 bg-surface px-4 py-2 text-center text-foreground">
+                        {row.before} ÷ 2
+                      </td>
+                      <td className="border-2 border-unit-6/40 bg-surface px-4 py-2 text-center font-bold text-foreground">
+                        {row.quotient}
+                      </td>
+                      <td className="border-2 border-unit-6/40 bg-correct-light px-4 py-2 text-center text-lg font-extrabold text-correct">
+                        {row.remainder}
+                      </td>
+                      <td className="px-3 py-2 text-left text-sm font-bold italic text-hint">
+                        {idx === 0
+                          ? "↓ start"
+                          : idx === result.rows.length - 1
+                            ? "↑ read up"
+                            : ""}
+                      </td>
+                    </tr>
+                  ))}
+                  <tr>
+                    <td
+                      colSpan={5}
+                      className="border-2 border-unit-6/40 bg-unit-6-light px-4 py-2 text-center text-xs font-bold uppercase tracking-wide text-unit-6-dark"
+                    >
+                      Quotient is 0 — stop. Read remainders from bottom to top.
+                    </td>
+                  </tr>
+                </tbody>
+              </table>
+            </div>
+          )}
+        </div>
+
+        <p className="mt-3 text-sm italic text-hint">
+          Read the remainders column <strong>from bottom to top</strong>. That string of 0s and 1s is your binary number.
+        </p>
+      </Card>
+
+      {/* Place value chart */}
+      <Card>
+        <div className="mb-3 flex flex-wrap items-center justify-between gap-2">
+          <p className="text-xs font-bold uppercase tracking-wider text-unit-6">
+            Place Value Chart (powers of 2)
+          </p>
+          <button
+            onClick={() => setChartHidden((v) => !v)}
+            className="rounded-md border border-border bg-surface px-2.5 py-1 text-xs font-semibold text-muted transition-colors hover:border-unit-6/50 hover:text-unit-6"
+          >
+            {chartHidden ? "Show Chart" : "Hide Chart"}
+          </button>
+        </div>
+
+        {!chartHidden && (
+          <div className="overflow-x-auto rounded-xl border-2 border-unit-6/30 bg-unit-6-light/40 p-3">
+            <table className="mx-auto border-collapse font-mono">
+              <tbody>
+                <tr>
+                  {COLUMNS.map((_, idx) => {
+                    const exp = COLUMNS.length - 1 - idx;
+                    return (
+                      <td
+                        key={`p-${exp}`}
+                        className="min-w-[64px] border-2 border-unit-6/40 bg-unit-6-light px-4 py-2 text-center text-sm font-bold text-unit-6-dark"
+                      >
+                        2<sup>{exp}</sup>
+                      </td>
+                    );
+                  })}
+                </tr>
+                <tr>
+                  {COLUMNS.map((v) => (
+                    <td
+                      key={`v-${v}`}
+                      className="min-w-[64px] border-2 border-unit-6/40 bg-surface px-4 py-2 text-center text-base font-bold text-unit-6"
+                    >
+                      {v}
+                    </td>
+                  ))}
+                </tr>
+                <tr>
+                  {chartBits.map((b, i) => (
+                    <td
+                      key={`d-${i}`}
+                      className={`min-w-[64px] border-2 border-unit-6/40 px-4 py-2 text-center text-2xl font-extrabold ${
+                        b === 1
+                          ? "bg-correct-light text-correct"
+                          : b === 0
+                            ? "bg-surface text-muted"
+                            : "bg-surface text-muted/60"
+                      }`}
+                    >
+                      {b === null ? "-" : b}
+                    </td>
+                  ))}
+                </tr>
+                <tr>
+                  {chartBits.map((b, i) => (
+                    <td
+                      key={`s-${i}`}
+                      className={`min-w-[64px] border-2 border-unit-6/40 px-4 py-2 text-center text-sm font-bold tracking-wider ${
+                        b === 1
+                          ? "bg-correct-light text-correct"
+                          : b === 0
+                            ? "bg-[#fafbfc] text-muted"
+                            : "bg-[#fafbfc] text-muted/60"
+                      }`}
+                    >
+                      {b === null ? "OFF" : b === 1 ? "ON" : "OFF"}
+                    </td>
+                  ))}
+                </tr>
+              </tbody>
+            </table>
+          </div>
+        )}
+      </Card>
+
+      {/* Answer banner */}
+      <Card
+        className={`flex min-h-[90px] flex-col items-center justify-center gap-2 text-center ${
+          submitted !== null && !answerHidden
+            ? "border-correct bg-correct-light"
+            : "border-unit-6/30 bg-unit-6-light/60"
+        }`}
+      >
+        {submitted === null ? (
+          <p className="font-mono text-base font-bold text-unit-6">
+            Type a denary number above and press Convert.
+          </p>
+        ) : answerHidden ? (
+          <p className="font-mono text-lg font-bold text-unit-6">
+            {submitted} = ?<sub>2</sub>  (press Show Answer)
+          </p>
+        ) : (
+          <p className="font-mono text-2xl font-extrabold text-correct">
+            {submitted} = {binaryString}<sub>2</sub> in binary
+          </p>
+        )}
+        <button
+          onClick={() => setAnswerHidden((v) => !v)}
+          className="mt-1 rounded-md border border-border bg-surface px-3 py-1 text-xs font-semibold text-muted transition-colors hover:border-unit-6/50 hover:text-unit-6"
+        >
+          {answerHidden ? "Show Answer" : "Hide Answer"}
+        </button>
+      </Card>
+
+      {/* Footer note */}
+      <Card className="border-l-4 border-l-unit-6 bg-unit-6-light/40">
+        <p className="text-sm text-unit-6-dark">
+          <strong>For students:</strong> solve on paper <em>first</em> using the division table in your worksheet. Type the denary number here only to <em>check</em>. The lesson is in the division and the bottom-up read, not the click.
+        </p>
+      </Card>
+    </div>
+  );
+}