<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Vertical Multiplication Step-by-Step</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
      padding: 12px;
      user-select: none;
    }

    .main-wrap {
      width: 100%;
      max-width: 440px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 12px;
    }

    /* Stepper Controls */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      flex-wrap: wrap;
    }
    .step-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      padding: 5px 12px;
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      transition: all 0.2s ease;
    }
    .step-btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.35);
    }
    .nav-btn {
      background: #f8fafc;
      border: 1px solid #cbd5e1;
      border-radius: 50%;
      width: 30px;
      height: 30px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 13px;
      cursor: pointer;
      color: #1e2945;
      transition: background 0.15s ease;
    }
    .nav-btn:hover {
      background: #e2e8f0;
    }

    /* Callout calculation pill */
    .callout-pill {
      min-height: 38px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 20px;
      padding: 6px 16px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      font-size: 14px;
      font-weight: 600;
      color: #0f172a;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
      transition: all 0.25s ease;
    }
    .callout-pill .highlight {
      color: #0284c7;
      font-weight: 700;
    }
    .callout-pill .carry-hl {
      color: #d97706;
      font-weight: 700;
    }

    /* Math Grid */
    .math-grid {
      display: grid;
      grid-template-columns: repeat(4, 48px);
      justify-content: center;
      row-gap: 3px;
      font-variant-numeric: tabular-nums;
    }

    .col-header {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      text-align: center;
      color: #94a3b8;
      padding-bottom: 2px;
    }

    .cell {
      height: 42px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 26px;
      font-weight: 600;
      color: #1e2945;
      border-radius: 8px;
      transition: all 0.25s ease;
      position: relative;
    }

    .cell.carry-cell {
      height: 28px;
      font-size: 14px;
      font-weight: 700;
      color: transparent;
    }

    .cell.carry-cell.show {
      color: #b45309;
      background: #fef3c7;
      border: 1px solid #fde68a;
    }

    .cell.operator {
      font-size: 22px;
      color: #64748b;
    }

    .cell.hl-factor {
      background: #e0f2fe;
      color: #0284c7;
      font-weight: 700;
    }

    .cell.hl-carry-target {
      box-shadow: 0 0 0 2px #f59e0b;
    }

    .math-bar {
      grid-column: 1 / span 4;
      height: 3px;
      background: #1e2945;
      border-radius: 2px;
      margin: 3px 0 5px 0;
    }

    .prod-cell {
      font-weight: 700;
      opacity: 0;
      transform: translateY(4px);
      transition: all 0.25s ease;
    }

    .prod-cell.show {
      opacity: 1;
      transform: translateY(0);
    }

    .prod-cell.active-digit {
      background: #dcfce7;
      color: #15803d;
    }
  </style>
</head>
<body>

<div class="main-wrap">
  
  <div class="controls">
    <button class="nav-btn" id="prevBtn" title="Previous Step">◀</button>
    <button class="step-btn active" data-step="0">Start</button>
    <button class="step-btn" data-step="1">1. Ones</button>
    <button class="step-btn" data-step="2">2. Tens</button>
    <button class="step-btn" data-step="3">3. Hundreds</button>
    <button class="step-btn" data-step="4">Total</button>
    <button class="nav-btn" id="nextBtn" title="Next Step">▶</button>
    <button class="nav-btn" id="playBtn" title="Auto Play">⏯</button>
  </div>

  
  <div class="callout-pill" id="callout">
    Multiply: 475 × 6
  </div>

  
  <div class="math-grid">
    
    <div class="col-header">Th</div>
    <div class="col-header">H</div>
    <div class="col-header">T</div>
    <div class="col-header">O</div>

    
    <div class="cell carry-cell"></div>
    <div class="cell carry-cell" id="carryH">+4</div>
    <div class="cell carry-cell" id="carryT">+3</div>
    <div class="cell carry-cell"></div>

    
    <div class="cell"></div>
    <div class="cell" id="digitH">4</div>
    <div class="cell" id="digitT">7</div>
    <div class="cell" id="digitO">5</div>

    
    <div class="cell operator">×</div>
    <div class="cell"></div>
    <div class="cell"></div>
    <div class="cell" id="digitMul">6</div>

    
    <div class="math-bar"></div>

    
    <div class="cell prod-cell" id="resTh">2</div>
    <div class="cell prod-cell" id="resH">8</div>
    <div class="cell prod-cell" id="resT">5</div>
    <div class="cell prod-cell" id="resO">0</div>
  </div>
</div>

<script>
  let currentStep = 0;
  let timer = null;

  const stepsData = [
    {
      callout: 'Multiply: 475 × 6',
      carries: { H: false, T: false },
      hlFactors: ['digitMul'],
      products: { Th: false, H: false, T: false, O: false },
      activeDigit: null
    },
    {
      callout: '<span class="highlight">6 × 5</span> = 30 → Write <span class="highlight">0</span>, Carry <span class="carry-hl">+3</span>',
      carries: { H: false, T: true },
      hlFactors: ['digitO', 'digitMul'],
      products: { Th: false, H: false, T: false, O: true },
      activeDigit: 'resO'
    },
    {
      callout: '<span class="highlight">6 × 7</span> + <span class="carry-hl">3</span> = 45 → Write <span class="highlight">5</span>, Carry <span class="carry-hl">+4</span>',
      carries: { H: true, T: true },
      hlFactors: ['digitT', 'digitMul'],
      products: { Th: false, H: false, T: true, O: true },
      activeDigit: 'resT'
    },
    {
      callout: '<span class="highlight">6 × 4</span> + <span class="carry-hl">4</span> = 28 → Write <span class="highlight">28</span>',
      carries: { H: true, T: true },
      hlFactors: ['digitH', 'digitMul'],
      products: { Th: true, H: true, T: true, O: true },
      activeDigit: 'resH'
    },
    {
      callout: '475 × 6 = <span class="highlight" style="font-size:16px;">2,850</span>',
      carries: { H: true, T: true },
      hlFactors: [],
      products: { Th: true, H: true, T: true, O: true },
      activeDigit: null
    }
  ];

  function renderStep(idx) {
    currentStep = idx;
    const data = stepsData[idx];

    // Buttons
    document.querySelectorAll('.step-btn').forEach((btn, i) => {
      btn.classList.toggle('active', i === idx);
    });

    // Callout
    document.getElementById('callout').innerHTML = data.callout;

    // Carries
    const carryH = document.getElementById('carryH');
    const carryT = document.getElementById('carryT');
    carryH.classList.toggle('show', data.carries.H);
    carryT.classList.toggle('show', data.carries.T);

    // Factors Highlight
    ['digitH', 'digitT', 'digitO', 'digitMul'].forEach(id => {
      const el = document.getElementById(id);
      el.classList.toggle('hl-factor', data.hlFactors.includes(id));
    });

    // Product Digits
    const prodMap = {
      Th: document.getElementById('resTh'),
      H: document.getElementById('resH'),
      T: document.getElementById('resT'),
      O: document.getElementById('resO')
    };

    Object.keys(prodMap).forEach(k => {
      const el = prodMap[k];
      el.classList.toggle('show', data.products[k]);
      el.classList.remove('active-digit');
    });

    if (data.activeDigit) {
      document.getElementById(data.activeDigit)?.classList.add('active-digit');
      if (data.activeDigit === 'resH') {
        document.getElementById('resTh')?.classList.add('active-digit');
      }
    }
  }

  function next() {
    renderStep((currentStep + 1) % stepsData.length);
  }

  function prev() {
    renderStep((currentStep - 1 + stepsData.length) % stepsData.length);
  }

  function togglePlay() {
    if (timer) {
      clearInterval(timer);
      timer = null;
      document.getElementById('playBtn').textContent = '▶';
    } else {
      next();
      timer = setInterval(next, 3200);
      document.getElementById('playBtn').textContent = '⏸';
    }
  }

  // Event Listeners
  document.querySelectorAll('.step-btn').forEach(btn => {
    btn.addEventListener('click', (e) => {
      if (timer) togglePlay();
      renderStep(parseInt(e.target.dataset.step, 10));
    });
  });

  document.getElementById('prevBtn').addEventListener('click', () => {
    if (timer) togglePlay();
    prev();
  });

  document.getElementById('nextBtn').addEventListener('click', () => {
    if (timer) togglePlay();
    next();
  });

  document.getElementById('playBtn').addEventListener('click', togglePlay);

  // Initial render
  renderStep(0);
</script>

</body>
</html>

Multiplying Two- and Three-Digit Numbers by a One-Digit Number

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e293b;
      background: #ffffff;
      padding: 12px;
      user-select: none;
    }
    
    .diagram-grid {
      display: grid;
      grid-template-columns: 1.15fr 0.85fr;
      gap: 16px;
      max-width: 640px;
      margin: 0 auto;
      align-items: start;
    }
    @media (max-width: 500px) {
      .diagram-grid {
        grid-template-columns: 1fr;
        gap: 14px;
      }
    }

    .panel-title {
      font-size: 13px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #64748b;
      margin-bottom: 8px;
      text-align: center;
    }

    /* Area Model */
    .area-box {
      border: 2px solid #cbd5e1;
      border-radius: 8px;
      overflow: hidden;
      display: flex;
      height: 90px;
      background: #f8fafc;
    }
    .area-col {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 4px;
      transition: all 0.3s ease;
      cursor: pointer;
      position: relative;
    }
    .area-hundreds { flex: 4; background: #ede9fe; border-right: 2px dashed #cbd5e1; }
    .area-tens { flex: 2; background: #e0f2fe; border-right: 2px dashed #cbd5e1; }
    .area-ones { flex: 1.2; background: #fef3c7; }

    .area-col.active {
      box-shadow: inset 0 0 0 3px currentColor;
    }
    .area-col.dimmed { opacity: 0.35; }

    .col-header {
      font-size: 12px;
      font-weight: 700;
      color: #475569;
      margin-bottom: 2px;
    }
    .col-calc {
      font-size: 11px;
      color: #64748b;
    }
    .col-val {
      font-size: 15px;
      font-weight: 800;
      margin-top: 2px;
    }

    .val-hundreds { color: #6d28d9; }
    .val-tens { color: #0284c7; }
    .val-ones { color: #d97706; }

    .area-side-label {
      position: absolute;
      left: -18px;
      top: 50%;
      transform: translateY(-50%);
      font-weight: 800;
      font-size: 14px;
      color: #334155;
    }
    .area-wrapper {
      position: relative;
      margin-left: 20px;
    }

    .area-sum {
      display: flex;
      justify-content: center;
      align-items: center;
      gap: 6px;
      margin-top: 10px;
      font-size: 13px;
      font-weight: 700;
      background: #f1f5f9;
      padding: 6px 10px;
      border-radius: 6px;
    }

    /* Standard Algorithm */
    .algo-card {
      background: #f8fafc;
      border: 2px solid #e2e8f0;
      border-radius: 8px;
      padding: 10px 14px;
      display: flex;
      flex-direction: column;
      align-items: center;
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    }

    .math-grid {
      display: grid;
      grid-template-columns: repeat(4, 18px);
      text-align: right;
      font-size: 18px;
      font-weight: 700;
      row-gap: 2px;
      line-height: 1.2;
    }

    .regroup-row {
      font-size: 12px;
      height: 16px;
      color: #64748b;
    }
    .carry-4 { color: #6d28d9; }
    .carry-3 { color: #0284c7; }

    .calc-row { color: #1e293b; }
    .mult-sign { text-align: left; }
    .line-row {
      grid-column: 1 / -1;
      height: 2px;
      background: #334155;
      margin: 3px 0;
    }
    .total-row {
      font-size: 20px;
      font-weight: 800;
      color: #0f172a;
    }

    .chunk-tag {
      display: inline-block;
      padding: 1px 4px;
      border-radius: 3px;
      transition: all 0.3s ease;
    }
    .chunk-tag.dimmed { opacity: 0.3; }
    .bg-h { background: #ede9fe; color: #6d28d9; }
    .bg-t { background: #e0f2fe; color: #0284c7; }
    .bg-o { background: #fef3c7; color: #d97706; }

    /* Interactive Stepper */
    .controls {
      display: flex;
      justify-content: center;
      gap: 6px;
      margin-top: 14px;
    }
    .step-btn {
      padding: 6px 12px;
      font-size: 12px;
      font-weight: 600;
      border-radius: 20px;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #475569;
      cursor: pointer;
      transition: all 0.2s ease;
    }
    .step-btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
      box-shadow: 0 2px 4px rgba(2, 132, 199, 0.2);
    }
  </style>
</head>
<body>

  <div class="diagram-grid">
    
    <div>
      <div class="panel-title">Expanded Area Model</div>
      <div class="area-wrapper">
        <div class="area-side-label">6</div>
        <div class="area-box">
          <div class="area-col area-hundreds" data-part="h" onclick="setStep('h')">
            <span class="col-header">400</span>
            <span class="col-calc">400 × 6</span>
            <span class="col-val val-hundreds">2,400</span>
          </div>
          <div class="area-col area-tens" data-part="t" onclick="setStep('t')">
            <span class="col-header">70</span>
            <span class="col-calc">70 × 6</span>
            <span class="col-val val-tens">420</span>
          </div>
          <div class="area-col area-ones" data-part="o" onclick="setStep('o')">
            <span class="col-header">5</span>
            <span class="col-calc">5 × 6</span>
            <span class="col-val val-ones">30</span>
          </div>
        </div>
      </div>

      <div class="area-sum">
        <span class="chunk-tag bg-h" data-part="h">2,400</span>
        <span>+</span>
        <span class="chunk-tag bg-t" data-part="t">420</span>
        <span>+</span>
        <span class="chunk-tag bg-o" data-part="o">30</span>
        <span>=</span>
        <strong>2,850</strong>
      </div>
    </div>

    
    <div>
      <div class="panel-title">Standard Algorithm</div>
      <div class="algo-card">
        <div class="math-grid">
          
          <div class="regroup-row"></div>
          <div class="regroup-row carry-4 chunk-tag bg-h" data-part="h">4</div>
          <div class="regroup-row carry-3 chunk-tag bg-t" data-part="t">3</div>
          <div class="regroup-row"></div>

          
          <div class="calc-row"></div>
          <div class="calc-row chunk-tag bg-h" data-part="h">4</div>
          <div class="calc-row chunk-tag bg-t" data-part="t">7</div>
          <div class="calc-row chunk-tag bg-o" data-part="o">5</div>

          
          <div class="calc-row mult-sign">×</div>
          <div class="calc-row"></div>
          <div class="calc-row"></div>
          <div class="calc-row">6</div>

          
          <div class="line-row"></div>

          
          <div class="total-row chunk-tag bg-h" data-part="h">2</div>
          <div class="total-row chunk-tag bg-h" data-part="h">8</div>
          <div class="total-row chunk-tag bg-t" data-part="t">5</div>
          <div class="total-row chunk-tag bg-o" data-part="o">0</div>
        </div>
      </div>
    </div>
  </div>

  
  <div class="controls">
    <button class="step-btn active" onclick="setStep('all')">All</button>
    <button class="step-btn" onclick="setStep('o')">1s (5 × 6 = 30)</button>
    <button class="step-btn" onclick="setStep('t')">10s (70 × 6 = 420)</button>
    <button class="step-btn" onclick="setStep('h')">100s (400 × 6 = 2400)</button>
  </div>

  <script>
    let currentStep = 'all';

    function setStep(step) {
      currentStep = step;

      // Update buttons
      const btns = document.querySelectorAll('.step-btn');
      btns.forEach(btn => {
        const text = btn.textContent.toLowerCase();
        if (step === 'all' && text.includes('all')) btn.classList.add('active');
        else if (step === 'o' && text.includes('1s')) btn.classList.add('active');
        else if (step === 't' && text.includes('10s')) btn.classList.add('active');
        else if (step === 'h' && text.includes('100s')) btn.classList.add('active');
        else btn.classList.remove('active');
      });

      // Update Area columns & chunks
      const areaCols = document.querySelectorAll('.area-col');
      areaCols.forEach(col => {
        const part = col.dataset.part;
        if (step === 'all') {
          col.classList.remove('dimmed', 'active');
        } else if (part === step) {
          col.classList.add('active');
          col.classList.remove('dimmed');
        } else {
          col.classList.remove('active');
          col.classList.add('dimmed');
        }
      });

      // Update tags in sum and algorithm
      const tags = document.querySelectorAll('.chunk-tag');
      tags.forEach(tag => {
        const part = tag.dataset.part;
        if (step === 'all' || part === step) {
          tag.classList.remove('dimmed');
        } else {
          tag.classList.add('dimmed');
        }
      });
    }
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Vertical Multiplication 38 x 4</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #f8f9fa;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 16px;
      user-select: none;
    }

    .header-controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      width: 100%;
      max-width: 440px;
    }

    .step-btn {
      flex: 1;
      padding: 8px 12px;
      border: 1px solid #e2e8f0;
      background: #ffffff;
      color: #64748b;
      font-size: 14px;
      font-weight: 600;
      border-radius: 8px;
      cursor: pointer;
      transition: all 0.2s ease;
      text-align: center;
    }

    .step-btn.active {
      background: #22b7ff;
      color: #ffffff;
      border-color: #22b7ff;
      box-shadow: 0 2px 6px rgba(34, 183, 255, 0.3);
    }

    .play-btn {
      width: 38px;
      height: 38px;
      display: flex;
      align-items: center;
      justify-content: center;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      color: #1e2945;
      cursor: pointer;
      font-size: 14px;
      transition: background 0.2s;
    }
    .play-btn:hover { background: #f1f5f9; }

    /* Main Stage */
    .stage {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 20px;
      width: 100%;
      max-width: 440px;
      margin: auto 0;
    }

    /* Math Grid Card */
    .math-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 16px 20px;
      box-shadow: 0 4px 12px rgba(0,0,0,0.03);
    }

    .grid-table {
      display: grid;
      grid-template-columns: 24px 38px 38px 38px;
      row-gap: 4px;
      text-align: center;
      font-size: 22px;
      font-weight: 700;
      align-items: center;
    }

    .col-header {
      font-size: 12px;
      font-weight: 600;
      color: #94a3b8;
      text-transform: uppercase;
      padding-bottom: 4px;
    }

    .cell {
      height: 36px;
      display: flex;
      align-items: center;
      justify-content: center;
      border-radius: 6px;
      transition: all 0.3s ease;
    }

    .cell.carry {
      color: #ef4444;
      font-size: 15px;
      font-weight: 800;
      opacity: 0;
      transform: translateY(4px);
    }
    .cell.carry.show {
      opacity: 1;
      transform: translateY(0);
    }

    .cell.highlight {
      background: #e0f2fe;
      color: #0284c7;
    }

    .cell.highlight-carry {
      background: #fee2e2;
      color: #dc2626;
      border-radius: 6px;
    }

    .cell.dim {
      opacity: 0.35;
    }

    .line-row {
      grid-column: 1 / span 4;
      height: 3px;
      background: #1e2945;
      border-radius: 2px;
      margin: 4px 0 6px 0;
    }

    .ans-digit {
      opacity: 0;
      transform: translateY(-4px);
      transition: all 0.3s ease;
    }
    .ans-digit.show {
      opacity: 1;
      transform: translateY(0);
      color: #0284c7;
    }

    /* Side Explanation Badge */
    .callout-card {
      flex: 1;
      display: flex;
      flex-direction: column;
      gap: 10px;
    }

    .formula-box {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 12px;
      box-shadow: 0 2px 8px rgba(0,0,0,0.02);
      opacity: 0.35;
      transition: all 0.3s ease;
    }

    .formula-box.active {
      opacity: 1;
      border-color: #22b7ff;
      box-shadow: 0 4px 12px rgba(34, 183, 255, 0.12);
      transform: scale(1.02);
    }

    .formula-title {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #64748b;
      margin-bottom: 4px;
    }

    .formula-math {
      font-size: 16px;
      font-weight: 700;
      color: #1e2945;
    }

    .badge-carry {
      color: #ef4444;
      font-weight: 800;
    }

    .badge-ans {
      color: #0284c7;
      font-weight: 800;
    }

    /* Progress bar */
    .dots-container {
      display: flex;
      gap: 8px;
    }
    .dot {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      background: #cbd5e1;
      cursor: pointer;
      transition: all 0.3s ease;
    }
    .dot.active {
      background: #22b7ff;
      width: 24px;
      border-radius: 5px;
    }
  </style>
</head>
<body>

  
  <div class="header-controls">
    <button class="step-btn active" id="btnStep1" onclick="setStep(0)">1. Ones</button>
    <button class="step-btn" id="btnStep2" onclick="setStep(1)">2. Tens</button>
    <button class="play-btn" id="playBtn" onclick="toggleAutoPlay()" title="Toggle Auto-play">⏸</button>
  </div>

  
  <div class="stage">
    
    <div class="math-card">
      <div class="grid-table">
        
        <div></div>
        <div class="col-header">H</div>
        <div class="col-header">T</div>
        <div class="col-header">O</div>

        
        <div></div>
        <div></div>
        <div class="cell carry" id="carryDigit">+3</div>
        <div></div>

        
        <div></div>
        <div></div>
        <div class="cell" id="topTens">3</div>
        <div class="cell" id="topOnes">8</div>

        
        <div class="cell">×</div>
        <div></div>
        <div></div>
        <div class="cell" id="multiplier">4</div>

        
        <div class="line-row"></div>

        
        <div></div>
        <div class="cell ans-digit" id="ansHundreds">1</div>
        <div class="cell ans-digit" id="ansTens">5</div>
        <div class="cell ans-digit" id="ansOnes">2</div>
      </div>
    </div>

    
    <div class="callout-card">
      <div class="formula-box active" id="boxStep1">
        <div class="formula-title">Multiply Ones</div>
        <div class="formula-math">4 × 8 = <span class="badge-carry">3</span><span class="badge-ans">2</span></div>
      </div>

      <div class="formula-box" id="boxStep2">
        <div class="formula-title">Multiply Tens</div>
        <div class="formula-math">(4 × 3) + <span class="badge-carry">3</span> = <span class="badge-ans">15</span></div>
      </div>
    </div>
  </div>

  
  <div class="dots-container">
    <div class="dot active" onclick="setStep(0)"></div>
    <div class="dot" onclick="setStep(1)"></div>
  </div>

  <script>
    let currentStep = 0;
    let isPlaying = true;
    let timer = null;

    const el = {
      carry: document.getElementById('carryDigit'),
      topTens: document.getElementById('topTens'),
      topOnes: document.getElementById('topOnes'),
      multiplier: document.getElementById('multiplier'),
      ansHundreds: document.getElementById('ansHundreds'),
      ansTens: document.getElementById('ansTens'),
      ansOnes: document.getElementById('ansOnes'),
      box1: document.getElementById('boxStep1'),
      box2: document.getElementById('boxStep2'),
      btn1: document.getElementById('btnStep1'),
      btn2: document.getElementById('btnStep2'),
      dots: document.querySelectorAll('.dot'),
      playBtn: document.getElementById('playBtn')
    };

    function render() {
      // Buttons & Indicators
      el.btn1.classList.toggle('active', currentStep === 0);
      el.btn2.classList.toggle('active', currentStep === 1);
      el.dots[0].classList.toggle('active', currentStep === 0);
      el.dots[1].classList.toggle('active', currentStep === 1);

      el.box1.classList.toggle('active', currentStep === 0);
      el.box2.classList.toggle('active', currentStep === 1);

      if (currentStep === 0) {
        // Step 1: 4 * 8 = 32
        el.carry.classList.add('show');
        el.carry.classList.remove('highlight-carry');

        el.topOnes.className = 'cell highlight';
        el.multiplier.className = 'cell highlight';
        el.topTens.className = 'cell dim';

        el.ansOnes.classList.add('show');
        el.ansTens.classList.remove('show');
        el.ansHundreds.classList.remove('show');
      } else {
        // Step 2: 4 * 3 + 3 = 15
        el.carry.classList.add('show', 'highlight-carry');

        el.topTens.className = 'cell highlight';
        el.multiplier.className = 'cell highlight';
        el.topOnes.className = 'cell dim';

        el.ansOnes.classList.add('show');
        el.ansTens.classList.add('show');
        el.ansHundreds.classList.add('show');
      }
    }

    function setStep(index) {
      currentStep = index;
      render();
      if (isPlaying) {
        restartTimer();
      }
    }

    function toggleAutoPlay() {
      isPlaying = !isPlaying;
      el.playBtn.textContent = isPlaying ? '⏸' : '▶';
      if (isPlaying) {
        restartTimer();
      } else {
        clearInterval(timer);
      }
    }

    function restartTimer() {
      clearInterval(timer);
      timer = setInterval(() => {
        currentStep = (currentStep + 1) % 2;
        render();
      }, 3200);
    }

    // Init
    render();
    restartTimer();
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }

    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: transparent;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
      padding: 12px;
      user-select: none;
    }

    .main-stage {
      display: flex;
      flex-direction: column;
      align-items: center;
      width: 100%;
      max-width: 360px;
      gap: 12px;
    }

    /* Equation formula pill */
    .formula-card {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 16px;
      font-size: 16px;
      font-weight: 700;
      letter-spacing: -0.2px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
      min-height: 44px;
      width: 100%;
      text-align: center;
    }

    .num-1 { color: #d97706; }
    .num-3 { color: #0891b2; }
    .num-5 { color: #ea580c; }
    .num-7 { color: #9333ea; }
    .eq-sym { color: #94a3b8; font-weight: 600; }
    .result { color: #0f172a; }

    /* Grid Area with Dimension Labels */
    .grid-container {
      position: relative;
      padding: 30px 16px 10px 64px;
      display: flex;
      justify-content: center;
      align-items: center;
    }

    .grid-board {
      display: grid;
      grid-template-columns: repeat(4, 44px);
      grid-template-rows: repeat(4, 44px);
      gap: 5px;
      background: #f1f5f9;
      padding: 6px;
      border-radius: 14px;
      border: 1px solid #e2e8f0;
    }

    .tile {
      border-radius: 8px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 13px;
      font-weight: 700;
      color: rgba(0, 0, 0, 0.45);
      transition: transform 0.28s ease, opacity 0.28s ease, background-color 0.28s ease;
      opacity: 0.12;
      transform: scale(0.88);
      background: #cbd5e1;
    }

    .tile.active {
      opacity: 1;
      transform: scale(1);
      box-shadow: 0 2px 5px rgba(0, 0, 0, 0.08);
    }

    .tile.layer-1.active { background: #fbbf24; }
    .tile.layer-2.active { background: #22d3ee; }
    .tile.layer-3.active { background: #fb923c; }
    .tile.layer-4.active { background: #c084fc; }

    /* Side Dimension Callouts */
    .dim-label {
      position: absolute;
      font-size: 11px;
      font-weight: 700;
      color: #475569;
      background: #ffffff;
      padding: 3px 8px;
      border-radius: 6px;
      border: 1px solid #cbd5e1;
      box-shadow: 0 1px 3px rgba(0,0,0,0.06);
      white-space: nowrap;
      z-index: 2;
      transition: top 0.25s ease, left 0.25s ease;
    }

    .dim-top {
      top: 4px;
      transform: translateX(-50%);
    }

    .dim-left {
      left: 6px;
      transform: translateY(-50%);
    }

    /* Controls */
    .controls {
      display: flex;
      gap: 8px;
      width: 100%;
      justify-content: center;
    }

    .btn {
      appearance: none;
      border: none;
      font-family: inherit;
      font-size: 14px;
      font-weight: 600;
      padding: 9px 16px;
      border-radius: 10px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: opacity 0.15s ease, background-color 0.15s ease;
    }

    .btn-primary {
      background: #0284c7;
      color: #ffffff;
      flex: 1;
    }

    .btn-primary:active {
      background: #0369a1;
    }

    .btn-secondary {
      background: #f1f5f9;
      color: #475569;
      border: 1px solid #cbd5e1;
    }

    .btn-secondary:active {
      background: #e2e8f0;
    }

    /* Step indicator dots */
    .stepper {
      display: flex;
      gap: 6px;
      align-items: center;
      margin-top: 2px;
    }

    .step-pill {
      font-size: 12px;
      font-weight: 700;
      padding: 4px 10px;
      border-radius: 12px;
      background: #f1f5f9;
      color: #64748b;
      cursor: pointer;
      border: 1px solid #e2e8f0;
      transition: all 0.2s ease;
    }

    .step-pill.active {
      background: #0f172a;
      color: #ffffff;
      border-color: #0f172a;
    }
  </style>
</head>
<body>
  <div class="main-stage">
    
    <div class="formula-card" id="formulaDisplay">
      <span class="num-1">1</span>
      <span class="eq-sym">=</span>
      <span class="result">1 (1²)</span>
    </div>

    
    <div class="grid-container">
      <div class="dim-label dim-top" id="dimTop">1 wide</div>
      <div class="dim-label dim-left" id="dimLeft">1 high</div>
      <div class="grid-board" id="gridBoard"></div>
    </div>

    
    <div class="stepper">
      <button class="step-pill active" onclick="setStep(1)">1²</button>
      <button class="step-pill" onclick="setStep(2)">2²</button>
      <button class="step-pill" onclick="setStep(3)">3²</button>
      <button class="step-pill" onclick="setStep(4)">4²</button>
    </div>

    
    <div class="controls">
      <button class="btn btn-primary" id="nextBtn" onclick="nextStep()">
        <span>+ Add Next Odd Number</span>
      </button>
      <button class="btn btn-secondary" onclick="resetGrid()">↺ Reset</button>
    </div>
  </div>

  <script>
    let currentStep = 1;

    // Grid coordinates mapped to layer indices (1 to 4)
    // Layer 1: (0,0) [1 tile]
    // Layer 2: (0,1), (1,1), (1,0) [3 tiles]
    // Layer 3: (0,2), (1,2), (2,2), (2,1), (2,0) [5 tiles]
    // Layer 4: (0,3), (1,3), (2,3), (3,3), (3,2), (3,1), (3,0) [7 tiles]
    const board = document.getElementById('gridBoard');
    const formulaDisplay = document.getElementById('formulaDisplay');
    const dimTop = document.getElementById('dimTop');
    const dimLeft = document.getElementById('dimLeft');
    const nextBtn = document.getElementById('nextBtn');
    const stepPills = document.querySelectorAll('.step-pill');

    const formulas = [
      '<span class="num-1">1</span> <span class="eq-sym">=</span> <span class="result">1 (1²)</span>',
      '<span class="num-1">1</span> <span class="eq-sym">+</span> <span class="num-3">3</span> <span class="eq-sym">=</span> <span class="result">4 (2²)</span>',
      '<span class="num-1">1</span> <span class="eq-sym">+</span> <span class="num-3">3</span> <span class="eq-sym">+</span> <span class="num-5">5</span> <span class="eq-sym">=</span> <span class="result">9 (3²)</span>',
      '<span class="num-1">1</span> <span class="eq-sym">+</span> <span class="num-3">3</span> <span class="eq-sym">+</span> <span class="num-5">5</span> <span class="eq-sym">+</span> <span class="num-7">7</span> <span class="eq-sym">=</span> <span class="result">16 (4²)</span>'
    ];

    const nextLabels = [
      '+ Add Next Odd Number (3)',
      '+ Add Next Odd Number (5)',
      '+ Add Next Odd Number (7)',
      'Restart ↺'
    ];

    // Build the 4x4 grid cells
    for (let r = 0; r < 4; r++) {
      for (let c = 0; c < 4; c++) {
        const layer = Math.max(r, c) + 1;
        const tile = document.createElement('div');
        tile.className = `tile layer-${layer}`;
        tile.dataset.layer = layer;
        board.appendChild(tile);
      }
    }

    function updateView() {
      // Update tiles
      const tiles = document.querySelectorAll('.tile');
      tiles.forEach(tile => {
        const layer = parseInt(tile.dataset.layer, 10);
        if (layer <= currentStep) {
          tile.classList.add('active');
        } else {
          tile.classList.remove('active');
        }
      });

      // Update formula
      formulaDisplay.innerHTML = formulas[currentStep - 1];

      // Update dimension tags
      dimTop.textContent = `${currentStep} wide`;
      dimLeft.textContent = `${currentStep} high`;

      // Update dimension tag positions dynamically for precise alignment
      // Container left padding: 64px, board padding: 6px, tile size: 44px, gap: 5px
      const tileStepSize = 44 + 5;
      const activeSpan = (currentStep * tileStepSize - 5);
      
      const leftOffset = 64 + 6 + (activeSpan / 2);
      const topOffset = 30 + 6 + (activeSpan / 2);

      dimTop.style.left = `${leftOffset}px`;
      dimLeft.style.top = `${topOffset}px`;

      // Update pills
      stepPills.forEach((pill, idx) => {
        pill.classList.toggle('active', idx + 1 === currentStep);
      });

      // Update button state
      nextBtn.innerHTML = `<span>${nextLabels[currentStep - 1]}</span>`;
    }

    function nextStep() {
      if (currentStep >= 4) {
        currentStep = 1;
      } else {
        currentStep++;
      }
      updateView();
    }

    function resetGrid() {
      currentStep = 1;
      updateView();
    }

    function setStep(step) {
      currentStep = step;
      updateView();
    }

    // Initialize
    updateView();
  </script>
</body>
</html>

Perfect Squares and Square Roots Through 15 × 15

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      padding: 12px;
      min-height: 100%;
      user-select: none;
    }

    /* Mode Toggle */
    .toggle-bar {
      display: flex;
      background: #f1f5f9;
      padding: 3px;
      border-radius: 999px;
      gap: 4px;
      margin-bottom: 8px;
    }
    .toggle-btn {
      border: none;
      background: transparent;
      padding: 6px 14px;
      border-radius: 999px;
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
      cursor: pointer;
      transition: all 0.25s ease;
    }
    .toggle-btn.active {
      background: #ffffff;
      color: #0284c7;
      box-shadow: 0 1px 4px rgba(0,0,0,0.1);
    }

    /* Main Stage */
    .stage {
      display: flex;
      flex-direction: row;
      align-items: center;
      justify-content: center;
      gap: 24px;
      width: 100%;
      max-width: 620px;
      flex: 1;
    }

    @media (max-width: 480px) {
      .stage {
        flex-direction: column;
        gap: 16px;
      }
    }

    /* Visual Grid Section */
    .grid-container {
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }
    .grid-wrapper {
      position: relative;
      padding: 24px 0 0 24px;
    }
    .side-label-top {
      position: absolute;
      top: 2px;
      left: 24px;
      right: 0;
      text-align: center;
      font-size: 14px;
      font-weight: 700;
      color: #0284c7;
      letter-spacing: 0.5px;
      transition: opacity 0.3s ease;
    }
    .side-label-left {
      position: absolute;
      top: 24px;
      left: 2px;
      bottom: 0;
      display: flex;
      align-items: center;
      font-size: 14px;
      font-weight: 700;
      color: #0284c7;
      writing-mode: vertical-rl;
      transform: rotate(180deg);
      transition: opacity 0.3s ease;
    }
    .tile-grid {
      display: grid;
      grid-template-columns: repeat(6, 26px);
      grid-template-rows: repeat(6, 26px);
      gap: 2px;
      background: #fef3c7;
      padding: 3px;
      border-radius: 8px;
      border: 2px solid #f59e0b;
      position: relative;
    }
    .tile {
      background: #fde047;
      border-radius: 3px;
      border: 1px solid #eab308;
      transition: all 0.3s ease;
    }
    .tile.edge-highlight {
      background: #38bdf8;
      border-color: #0284c7;
    }
    .tile.area-highlight {
      background: #fde047;
      border-color: #ca8a04;
    }
    .grid-caption {
      margin-top: 8px;
      font-size: 13px;
      font-weight: 700;
      color: #b45309;
      background: #fef3c7;
      padding: 3px 10px;
      border-radius: 999px;
      border: 1px solid #fde68a;
      transition: all 0.3s ease;
    }

    /* Notation & Callouts Section */
    .notation-container {
      display: flex;
      flex-direction: column;
      align-items: center;
      min-width: 200px;
    }

    .formula-card {
      background: #f8fafc;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 16px 20px;
      display: flex;
      flex-direction: column;
      gap: 16px;
      width: 100%;
    }

    .math-display {
      display: flex;
      align-items: baseline;
      justify-content: center;
      font-size: 34px;
      font-weight: 800;
      font-family: 'Cambria Math', 'KaTeX_Math', 'Times New Roman', serif;
      min-height: 48px;
    }

    /* Root Anatomy Elements */
    .radical-part {
      color: #64748b;
      position: relative;
      display: inline-flex;
      align-items: baseline;
    }
    .rad-symbol {
      font-size: 38px;
      color: #6366f1;
      margin-right: -2px;
    }
    .rad-vinculum {
      border-top: 3px solid #6366f1;
      padding-top: 2px;
      margin-left: -2px;
    }
    .rad-value {
      color: #d97706;
      font-size: 34px;
    }
    .math-equals {
      margin: 0 10px;
      color: #94a3b8;
    }
    .math-result {
      color: #0284c7;
      font-size: 34px;
    }

    /* Square Mode Anatomy Elements */
    .base-val {
      color: #0284c7;
    }
    .exp-val {
      color: #6366f1;
      font-size: 22px;
      vertical-align: super;
      margin-left: 2px;
    }
    .pow-val {
      color: #d97706;
    }

    /* Anatomy Callout Legend */
    .callout-list {
      display: flex;
      flex-direction: column;
      gap: 8px;
      width: 100%;
    }
    .callout-item {
      display: flex;
      align-items: center;
      gap: 8px;
      font-size: 12px;
      font-weight: 600;
      line-height: 1.2;
    }
    .callout-pill {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      min-width: 24px;
      height: 24px;
      padding: 0 6px;
      border-radius: 6px;
      font-size: 13px;
      font-weight: 800;
      font-family: monospace;
    }
    .pill-purple { background: #ede9fe; color: #6366f1; border: 1px solid #ddd6fe; }
    .pill-amber { background: #fef3c7; color: #d97706; border: 1px solid #fde68a; }
    .pill-blue { background: #e0f2fe; color: #0284c7; border: 1px solid #bae6fd; }

    .callout-text {
      display: flex;
      flex-direction: column;
    }
    .callout-title {
      font-size: 12px;
      font-weight: 700;
      color: #1e2945;
    }
    .callout-sub {
      font-size: 11px;
      color: #64748b;
      font-weight: 500;
    }
  </style>
</head>
<body>

  
  <div class="toggle-bar">
    <button id="btnRoot" class="toggle-btn active" onclick="setMode('root')">√ Finding Root</button>
    <button id="btnSquare" class="toggle-btn" onclick="setMode('square')">x² Squaring</button>
  </div>

  
  <div class="stage">
    
    <div class="grid-container">
      <div class="grid-wrapper">
        <div id="sideTop" class="side-label-top">6 units</div>
        <div id="sideLeft" class="side-label-left">6 units</div>
        <div id="grid" class="tile-grid"></div>
      </div>
      <div id="gridCaption" class="grid-caption">Total Area = 36 tiles</div>
    </div>

    
    <div class="notation-container">
      <div class="formula-card">
        
        
        <div id="formulaRoot" class="math-display">
          <span class="radical-part">
            <span class="rad-symbol">√</span>
            <span class="rad-vinculum"><span class="rad-value">36</span></span>
          </span>
          <span class="math-equals">=</span>
          <span class="math-result">6</span>
        </div>

        
        <div id="formulaSquare" class="math-display" style="display: none;">
          <span>
            <span class="base-val">6</span><span class="exp-val">2</span>
          </span>
          <span class="math-equals">=</span>
          <span class="pow-val">36</span>
        </div>

        
        <div id="calloutsRoot" class="callout-list">
          <div class="callout-item">
            <span class="callout-pill pill-purple">√</span>
            <div class="callout-text">
              <span class="callout-title">Radical Symbol</span>
              <span class="callout-sub">Root operation</span>
            </div>
          </div>
          <div class="callout-item">
            <span class="callout-pill pill-amber">36</span>
            <div class="callout-text">
              <span class="callout-title">Radicand</span>
              <span class="callout-sub">Total area of square</span>
            </div>
          </div>
          <div class="callout-item">
            <span class="callout-pill pill-blue">6</span>
            <div class="callout-text">
              <span class="callout-title">Square Root</span>
              <span class="callout-sub">Side length of square</span>
            </div>
          </div>
        </div>

        
        <div id="calloutsSquare" class="callout-list" style="display: none;">
          <div class="callout-item">
            <span class="callout-pill pill-blue">6</span>
            <div class="callout-text">
              <span class="callout-title">Base</span>
              <span class="callout-sub">Side length of square</span>
            </div>
          </div>
          <div class="callout-item">
            <span class="callout-pill pill-purple">²</span>
            <div class="callout-text">
              <span class="callout-title">Exponent</span>
              <span class="callout-sub">Multiply by itself</span>
            </div>
          </div>
          <div class="callout-item">
            <span class="callout-pill pill-amber">36</span>
            <div class="callout-text">
              <span class="callout-title">Perfect Square</span>
              <span class="callout-sub">Total area formed</span>
            </div>
          </div>
        </div>

      </div>
    </div>
  </div>

  <script>
    // Build 6x6 Grid
    const gridEl = document.getElementById('grid');
    for (let i = 0; i < 36; i++) {
      const tile = document.createElement('div');
      tile.className = 'tile area-highlight';
      tile.dataset.row = Math.floor(i / 6);
      tile.dataset.col = i % 6;
      gridEl.appendChild(tile);
    }

    let currentMode = 'root';

    function setMode(mode) {
      currentMode = mode;
      const btnRoot = document.getElementById('btnRoot');
      const btnSquare = document.getElementById('btnSquare');
      const formulaRoot = document.getElementById('formulaRoot');
      const formulaSquare = document.getElementById('formulaSquare');
      const calloutsRoot = document.getElementById('calloutsRoot');
      const calloutsSquare = document.getElementById('calloutsSquare');
      const gridCaption = document.getElementById('gridCaption');
      const tiles = document.querySelectorAll('.tile');

      if (mode === 'root') {
        btnRoot.classList.add('active');
        btnSquare.classList.remove('active');
        
        formulaRoot.style.display = 'flex';
        formulaSquare.style.display = 'none';
        calloutsRoot.style.display = 'flex';
        calloutsSquare.style.display = 'none';
        
        gridCaption.textContent = '√36 Area → 6 Side';
        gridCaption.style.background = '#e0f2fe';
        gridCaption.style.color = '#0284c7';
        gridCaption.style.borderColor = '#bae6fd';

        // Animate highlight: pulse whole area, then highlight side length
        tiles.forEach(t => {
          t.classList.remove('edge-highlight');
          t.classList.add('area-highlight');
        });
        setTimeout(() => {
          tiles.forEach(t => {
            if (t.dataset.row === '0') {
              t.classList.add('edge-highlight');
            }
          });
        }, 300);

      } else {
        btnSquare.classList.add('active');
        btnRoot.classList.remove('active');
        
        formulaRoot.style.display = 'none';
        formulaSquare.style.display = 'flex';
        calloutsRoot.style.display = 'none';
        calloutsSquare.style.display = 'flex';
        
        gridCaption.textContent = '6 Side → 6² = 36 Area';
        gridCaption.style.background = '#fef3c7';
        gridCaption.style.color = '#b45309';
        gridCaption.style.borderColor = '#fde68a';

        // Animate highlight: start from edge, unfold to all 36
        tiles.forEach(t => {
          if (t.dataset.row === '0') {
            t.classList.add('edge-highlight');
          } else {
            t.classList.remove('edge-highlight');
          }
        });
        setTimeout(() => {
          tiles.forEach(t => {
            t.classList.remove('edge-highlight');
            t.classList.add('area-highlight');
          });
        }, 400);
      }
    }

    // Initialize with root highlight sequence
    setMode('root');
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      user-select: none;
    }

    body {
      width: 100%;
      min-height: 100%;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 12px;
    }

    .tabs {
      display: flex;
      flex-wrap: wrap;
      gap: 6px;
      justify-content: center;
      width: 100%;
      max-width: 420px;
      margin-bottom: 12px;
    }

    .tab-btn {
      flex: 1 1 calc(20% - 6px);
      min-width: 58px;
      padding: 8px 4px;
      font-size: 13px;
      font-weight: 700;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      background: #f8fafc;
      color: #475569;
      cursor: pointer;
      text-align: center;
      transition: background-color 0.2s, color 0.2s, border-color 0.2s;
    }

    .tab-btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
    }

    .model-wrapper {
      width: 100%;
      max-width: 320px;
      display: grid;
      grid-template-columns: 28px 1fr;
      grid-template-rows: 28px 1fr;
      gap: 4px;
      margin: 0 auto;
    }

    .dim-corner {
      grid-column: 1;
      grid-row: 1;
    }

    .dim-top {
      grid-column: 2;
      grid-row: 1;
      display: grid;
      gap: 4px;
      align-items: center;
      text-align: center;
      font-weight: 700;
      font-size: 14px;
      color: #64748b;
    }

    .dim-left {
      grid-column: 1;
      grid-row: 2;
      display: grid;
      gap: 4px;
      align-items: center;
      text-align: center;
      font-weight: 700;
      font-size: 14px;
      color: #64748b;
    }

    .grid-container {
      grid-column: 2;
      grid-row: 2;
      aspect-ratio: 1 / 1;
      display: grid;
      gap: 4px;
      width: 100%;
    }

    .cell {
      border-radius: 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 4px;
      text-align: center;
      border: 1.5px solid transparent;
      transition: all 0.25s ease;
    }

    .cell-tl {
      background: #e0f2fe;
      border-color: #7dd3fc;
      color: #0369a1;
    }

    .cell-tr, .cell-bl {
      background: #f3e8ff;
      border-color: #d8b4fe;
      color: #7e22ce;
    }

    .cell-br {
      background: #fef3c7;
      border-color: #fcd34d;
      color: #b45309;
    }

    .calc-txt {
      font-size: 12px;
      font-weight: 600;
      opacity: 0.85;
      line-height: 1.1;
    }

    .area-txt {
      font-size: 16px;
      font-weight: 800;
      line-height: 1.2;
    }

    .breakdown-bar {
      margin-top: 12px;
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: center;
      gap: 4px 6px;
      font-size: 14px;
      font-weight: 700;
    }

    .tag {
      padding: 3px 8px;
      border-radius: 6px;
      font-size: 13px;
    }

    .tag-tl { background: #e0f2fe; color: #0369a1; }
    .tag-tr { background: #f3e8ff; color: #7e22ce; }
    .tag-br { background: #fef3c7; color: #b45309; }

    .summary-card {
      margin-top: 10px;
      width: 100%;
      max-width: 320px;
      display: flex;
      align-items: center;
      justify-content: space-around;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 12px;
      font-size: 16px;
      font-weight: 800;
    }

    .sq-val { color: #0284c7; }
    .sqrt-val { color: #059669; }
  </style>
</head>
<body>

  <div class="tabs" id="tabGroup">
    <button class="tab-btn active" data-n="1">11²</button>
    <button class="tab-btn" data-n="2">12²</button>
    <button class="tab-btn" data-n="3">13²</button>
    <button class="tab-btn" data-n="4">14²</button>
    <button class="tab-btn" data-n="5">15²</button>
  </div>

  <div class="model-wrapper">
    <div class="dim-corner"></div>
    <div class="dim-top" id="dimTop">
      <div>10</div>
      <div id="topN">1</div>
    </div>
    <div class="dim-left" id="dimLeft">
      <div>10</div>
      <div id="leftN">1</div>
    </div>

    <div class="grid-container" id="gridArea">
      <div class="cell cell-tl">
        <div class="calc-txt">10 × 10</div>
        <div class="area-txt">100</div>
      </div>
      <div class="cell cell-tr">
        <div class="calc-txt" id="trCalc">10 × 1</div>
        <div class="area-txt" id="trArea">10</div>
      </div>
      <div class="cell cell-bl">
        <div class="calc-txt" id="blCalc">1 × 10</div>
        <div class="area-txt" id="blArea">10</div>
      </div>
      <div class="cell cell-br">
        <div class="calc-txt" id="brCalc">1 × 1</div>
        <div class="area-txt" id="brArea">1</div>
      </div>
    </div>
  </div>

  <div class="breakdown-bar">
    <span class="tag tag-tl">100</span>
    <span>+</span>
    <span class="tag tag-tr" id="tagTR">10</span>
    <span>+</span>
    <span class="tag tag-tr" id="tagBL">10</span>
    <span>+</span>
    <span class="tag tag-br" id="tagBR">1</span>
    <span>=</span>
    <span id="sumTotal" style="color: #0f172a;">121</span>
  </div>

  <div class="summary-card">
    <div class="sq-val" id="sumSquare">11² = 121</div>
    <div style="color: #cbd5e1;">|</div>
    <div class="sqrt-val" id="sumSqrt">√121 = 11</div>
  </div>

  <script>
    const buttons = document.querySelectorAll('.tab-btn');
    const dimTop = document.getElementById('dimTop');
    const dimLeft = document.getElementById('dimLeft');
    const gridArea = document.getElementById('gridArea');

    const topN = document.getElementById('topN');
    const leftN = document.getElementById('leftN');

    const trCalc = document.getElementById('trCalc');
    const trArea = document.getElementById('trArea');
    const blCalc = document.getElementById('blCalc');
    const blArea = document.getElementById('blArea');
    const brCalc = document.getElementById('brCalc');
    const brArea = document.getElementById('brArea');

    const tagTR = document.getElementById('tagTR');
    const tagBL = document.getElementById('tagBL');
    const tagBR = document.getElementById('tagBR');
    const sumTotal = document.getElementById('sumTotal');

    const sumSquare = document.getElementById('sumSquare');
    const sumSqrt = document.getElementById('sumSqrt');

    function updateDiagram(n) {
      const side = 10 + n;
      const total = side * side;
      const cross = 10 * n;
      const n2 = n * n;

      const colTemplate = `10fr ${Math.max(n * 1.5, 2.5)}fr`;
      dimTop.style.gridTemplateColumns = colTemplate;
      dimLeft.style.gridTemplateRows = colTemplate;
      gridArea.style.gridTemplateColumns = colTemplate;
      gridArea.style.gridTemplateRows = colTemplate;

      topN.textContent = n;
      leftN.textContent = n;

      trCalc.textContent = `10 × ${n}`;
      trArea.textContent = cross;

      blCalc.textContent = `${n} × 10`;
      blArea.textContent = cross;

      brCalc.textContent = `${n} × ${n}`;
      brArea.textContent = n2;

      tagTR.textContent = cross;
      tagBL.textContent = cross;
      tagBR.textContent = n2;
      sumTotal.textContent = total;

      sumSquare.textContent = `${side}² = ${total}`;
      sumSqrt.textContent = `√${total} = ${side}`;
    }

    buttons.forEach(btn => {
      btn.addEventListener('click', () => {
        buttons.forEach(b => b.classList.remove('active'));
        btn.classList.add('active');
        const n = parseInt(btn.getAttribute('data-n'), 10);
        updateDiagram(n);
      });
    });

    updateDiagram(1);
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      -webkit-tap-highlight-color: transparent;
    }

    body {
      width: 100%;
      background: #ffffff;
      color: #1e2945;
      font-family: system-ui, -apple-system, sans-serif;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 16px 8px;
    }

    .grids-container {
      display: flex;
      flex-wrap: wrap;
      justify-content: center;
      align-items: flex-end;
      gap: 12px;
      width: 100%;
      max-width: 640px;
    }

    .square-card {
      display: flex;
      flex-direction: column;
      align-items: center;
      background: #f8fafc;
      border: 1.5px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px 8px 8px;
      cursor: pointer;
      user-select: none;
      transition: border-color 0.25s ease, box-shadow 0.25s ease, transform 0.2s ease;
    }

    .square-card:hover {
      border-color: #22b7ff;
      box-shadow: 0 4px 12px rgba(34, 183, 255, 0.15);
    }

    .square-card.active {
      border-color: #4f46e5;
      background: #ffffff;
      box-shadow: 0 4px 16px rgba(79, 70, 229, 0.2);
    }

    .formula {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      margin-bottom: 8px;
      white-space: nowrap;
      text-align: center;
    }

    .formula .exp {
      color: #4f46e5;
      font-weight: 800;
    }

    .grid-wrapper {
      display: grid;
      grid-template-columns: auto 1fr;
      grid-template-rows: auto 1fr;
      gap: 4px;
      align-items: center;
      justify-items: center;
    }

    .label-top {
      grid-column: 2;
      grid-row: 1;
      font-size: 12px;
      font-weight: 700;
      color: #22b7ff;
      line-height: 1;
      padding-bottom: 2px;
    }

    .label-left {
      grid-column: 1;
      grid-row: 2;
      font-size: 12px;
      font-weight: 700;
      color: #4f46e5;
      line-height: 1;
      padding-right: 2px;
    }

    .grid-matrix {
      grid-column: 2;
      grid-row: 2;
      display: grid;
      gap: 2.5px;
    }

    .tile {
      width: 14px;
      height: 14px;
      border-radius: 3px;
      background: linear-gradient(135deg, #22b7ff, #4f46e5);
      transition: background 0.2s ease, transform 0.2s ease;
    }

    .pulse {
      animation: blockPulse 0.45s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
    }

    @keyframes blockPulse {
      0% { transform: scale(1); filter: brightness(1); }
      50% { transform: scale(1.22); filter: brightness(1.3) drop-shadow(0 0 3px #22b7ff); }
      100% { transform: scale(1); filter: brightness(1); }
    }

    @media (max-width: 480px) {
      .grids-container {
        gap: 8px;
      }
      .square-card {
        padding: 8px 6px 6px;
      }
      .tile {
        width: 12px;
        height: 12px;
        gap: 2px;
      }
      .formula {
        font-size: 12px;
      }
    }
  </style>
</head>
<body>

  <div class="grids-container" id="gridContainer"></div>

  <script>
    const data = [
      { n: 1, text: "1×1 = 1", exp: "1²" },
      { n: 2, text: "2×2 = 4", exp: "2²" },
      { n: 3, text: "3×3 = 9", exp: "3²" },
      { n: 4, text: "4×4 = 16", exp: "4²" },
      { n: 5, text: "5×5 = 25", exp: "5²" }
    ];

    const container = document.getElementById('gridContainer');

    data.forEach((item, index) => {
      const card = document.createElement('div');
      card.className = 'square-card' + (item.n === 4 ? ' active' : '');
      card.dataset.n = item.n;

      const formula = document.createElement('div');
      formula.className = 'formula';
      formula.innerHTML = `${item.text} <span class="exp">(${item.exp})</span>`;
      card.appendChild(formula);

      const wrapper = document.createElement('div');
      wrapper.className = 'grid-wrapper';

      const labelTop = document.createElement('div');
      labelTop.className = 'label-top';
      labelTop.textContent = item.n;
      wrapper.appendChild(labelTop);

      const labelLeft = document.createElement('div');
      labelLeft.className = 'label-left';
      labelLeft.textContent = item.n;
      wrapper.appendChild(labelLeft);

      const matrix = document.createElement('div');
      matrix.className = 'grid-matrix';
      matrix.style.gridTemplateColumns = `repeat(${item.n}, 1fr)`;

      for (let r = 0; r < item.n; r++) {
        for (let c = 0; c < item.n; c++) {
          const tile = document.createElement('div');
          tile.className = 'tile';
          tile.dataset.row = r;
          tile.dataset.col = c;
          matrix.appendChild(tile);
        }
      }

      wrapper.appendChild(matrix);
      card.appendChild(wrapper);

      function triggerPulse() {
        document.querySelectorAll('.square-card').forEach(c => c.classList.remove('active'));
        card.classList.add('active');

        const tiles = matrix.querySelectorAll('.tile');
        tiles.forEach((t) => {
          t.classList.remove('pulse');
          const r = parseInt(t.dataset.row, 10);
          const c = parseInt(t.dataset.col, 10);
          const delay = (r + c) * 45;
          setTimeout(() => {
            t.classList.add('pulse');
          }, delay);
        });
      }

      card.addEventListener('click', triggerPulse);
      container.appendChild(card);
    });
  </script>
</body>
</html>

Understanding Multiplicative Comparison

Writing Multiplicative Comparison Equations

Multiplying by Multiples of 10

Multiplying by Multiples of 100

Multiplying by 1,000 Using Place Value

Using Place Value to Multiply by 10 and 100

math

Multiplicative Comparison and Powers of 10

Understanding Place Value Relationships in Multi-Digit Numbers

Multiplying Whole Numbers by 10, 100, and 1,000

Dividing Multiples of 10 and 100 Using Place Value Facts

Patterns in Zeros When Multiplying by Powers of 10

Understanding the Millions and Billions Periods

Value Versus Place Value in Ten-Digit Numbers

Exploring the One-Tenth Relationship Across Places

Place Value and Powers of Ten to Billions

Calcul mental : ajouter ou soustraire des unités à un décimal sans retenue

Calcul mental : ajouter ou soustraire des dizaines et centaines à un décimal

Calcul mental : ajouter ou soustraire des dixièmes et centièmes sans retenue

Multiplier un nombre entier par 10, 100 ou 1 000

Multiplier un nombre décimal par 10

Diviser un nombre décimal par 10

Calcul mental et numération décimale

Ajouter ou soustraire 9 et 19 par compensation

Ajouter ou soustraire 8 et 18 par compensation

Ajouter ou soustraire 28, 29, 38, 39 jusqu'à 98 ou 99

Multiplier un chiffre par un nombre entier de dizaines ou centaines

Multiplier des dizaines, des centaines et des milliers entre elles

Utiliser la distributivité simple pour multiplier mentalement

Utiliser la distributivité avec soustraction : multiplier par 19 ou 29

Diviser un nombre entier par 4 en prenant la moitié de la moitié

Diviser un nombre entier par 8 en prenant trois fois la moitié

Défis et stratégies croisées de calcul mental sur les entiers

Calcul mental sur les entiers : compensations, distributivité et ordres de grandeur

OGM.5.NBT.4

Aligned learning resources

Related diagrams