<!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;
      user-select: none;
    }

    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: transparent;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
      padding: 8px;
    }

    .nav-tabs {
      display: flex;
      gap: 6px;
      margin-bottom: 12px;
    }

    .tab-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;
    }

    .tab-btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.3);
    }

    .stage {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      width: 100%;
      max-width: 580px;
    }

    .side-box {
      flex: 1;
      background: #f8fafc;
      border: 1.5px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 8px;
      min-width: 0;
    }

    .expr-title {
      font-size: 18px;
      font-weight: 700;
      color: #0f172a;
      letter-spacing: -0.2px;
    }

    .expr-sub {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      text-align: center;
      margin-top: -4px;
    }

    .tile-group {
      background: #ffffff;
      border: 1.5px dashed #cbd5e1;
      border-radius: 8px;
      padding: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 5px;
      width: 100%;
      max-width: 190px;
    }

    .tile-x {
      width: 44px;
      height: 24px;
      background: #2563eb;
      border-radius: 4px;
      color: #ffffff;
      font-size: 14px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      box-shadow: 0 1px 3px rgba(37, 99, 235, 0.25);
      transition: opacity 0.25s ease, transform 0.25s ease, filter 0.25s ease;
      flex-shrink: 0;
    }

    .tile-1 {
      width: 24px;
      height: 24px;
      background: #16a34a;
      border-radius: 4px;
      color: #ffffff;
      font-size: 13px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      box-shadow: 0 1px 3px rgba(22, 163, 74, 0.25);
      transition: opacity 0.25s ease, transform 0.25s ease, filter 0.25s ease;
      flex-shrink: 0;
    }

    .unit-grid {
      display: grid;
      grid-template-columns: repeat(3, 24px);
      gap: 5px;
    }

    .units-row {
      display: flex;
      gap: 5px;
    }

    .center-eq {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 4px;
      flex-shrink: 0;
    }

    .eq-sign {
      width: 36px;
      height: 36px;
      border-radius: 50%;
      background: #ecfdf5;
      border: 2px solid #10b981;
      color: #059669;
      font-size: 22px;
      font-weight: 800;
      display: flex;
      align-items: center;
      justify-content: center;
      box-shadow: 0 0 12px rgba(16, 185, 129, 0.35);
    }

    .badge {
      margin-top: 12px;
      background: #ecfdf5;
      border: 1.5px solid #a7f3d0;
      color: #065f46;
      font-size: 13px;
      font-weight: 700;
      padding: 6px 14px;
      border-radius: 20px;
      text-align: center;
      display: flex;
      align-items: center;
      gap: 6px;
      box-shadow: 0 1px 3px rgba(16, 185, 129, 0.15);
    }

    .dim {
      opacity: 0.25;
      filter: grayscale(80%);
      transform: scale(0.94);
    }

    .highlight {
      transform: scale(1.06);
      filter: drop-shadow(0 0 4px rgba(0, 0, 0, 0.2));
    }
  </style>
</head>
<body>

  <div class="nav-tabs">
    <button class="tab-btn active" onclick="setMode('all')">All</button>
    <button class="tab-btn" onclick="setMode('x')">x-tiles</button>
    <button class="tab-btn" onclick="setMode('1')">1-tiles</button>
  </div>

  <div class="stage">
    
    <div class="side-box">
      <div class="expr-title">2(x + 3)</div>
      <div class="expr-sub">2 groups of (x + 3)</div>

      <div class="tile-group">
        <div class="tile-x" data-type="x">x</div>
        <div class="units-row">
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
        </div>
      </div>

      <div class="tile-group">
        <div class="tile-x" data-type="x">x</div>
        <div class="units-row">
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
        </div>
      </div>
    </div>

    
    <div class="center-eq">
      <div class="eq-sign">=</div>
    </div>

    
    <div class="side-box">
      <div class="expr-title">2x + 6</div>
      <div class="expr-sub">Combined tiles</div>

      <div class="tile-group">
        <div class="tile-x" data-type="x">x</div>
        <div class="tile-x" data-type="x">x</div>
      </div>

      <div class="tile-group">
        <div class="unit-grid">
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
          <div class="tile-1" data-type="1">1</div>
        </div>
      </div>
    </div>
  </div>

  <div class="badge" id="badgeText">
    <span>✓</span>
    <span>Equivalent: 2 x-tiles & 6 unit tiles</span>
  </div>

  <script>
    function setMode(mode) {
      const tabs = document.querySelectorAll('.tab-btn');
      tabs.forEach((tab, i) => {
        const matches = (mode === 'all' && i === 0) || (mode === 'x' && i === 1) || (mode === '1' && i === 2);
        tab.classList.toggle('active', matches);
      });

      const xTiles = document.querySelectorAll('[data-type="x"]');
      const unitTiles = document.querySelectorAll('[data-type="1"]');
      const badge = document.getElementById('badgeText');

      if (mode === 'all') {
        xTiles.forEach(t => { t.classList.remove('dim', 'highlight'); });
        unitTiles.forEach(t => { t.classList.remove('dim', 'highlight'); });
        badge.innerHTML = '<span>✓</span><span>Equivalent: 2 x-tiles & 6 unit tiles</span>';
      } else if (mode === 'x') {
        xTiles.forEach(t => { t.classList.remove('dim'); t.classList.add('highlight'); });
        unitTiles.forEach(t => { t.classList.remove('highlight'); t.classList.add('dim'); });
        badge.innerHTML = '<span>✓</span><span>2 x-tiles on both sides</span>';
      } else if (mode === '1') {
        xTiles.forEach(t => { t.classList.remove('highlight'); t.classList.add('dim'); });
        unitTiles.forEach(t => { t.classList.remove('dim'); t.classList.add('highlight'); });
        badge.innerHTML = '<span>✓</span><span>6 unit tiles on both sides</span>';
      }
    }
  </script>
</body>
</html>

Determining Equivalent Expressions with Concrete Models

<!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 {
      width: 100%;
      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 16px;
      min-height: 100%;
      user-select: none;
    }

    /* Stepper Controls */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      width: 100%;
      max-width: 420px;
    }
    .step-btn {
      flex: 1;
      padding: 6px 10px;
      font-size: 13px;
      font-weight: 600;
      background: #f1f5f9;
      color: #64748b;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      cursor: pointer;
      text-align: center;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
    }
    .step-btn.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
    }
    .play-btn {
      width: 34px;
      height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
      background: #f1f5f9;
      color: #1e2945;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      cursor: pointer;
      font-size: 13px;
    }

    /* Expression Header */
    .expression-box {
      margin-top: 6px;
      font-size: 24px;
      font-weight: 700;
      letter-spacing: 0.5px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      height: 36px;
    }
    .term-x {
      color: #2563eb;
    }
    .term-const {
      color: #10b981;
    }
    .term-op {
      color: #64748b;
      font-weight: 500;
    }

    /* Tile Stage Area */
    .stage {
      position: relative;
      width: 100%;
      max-width: 380px;
      height: 140px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      display: flex;
      align-items: center;
      justify-content: center;
      overflow: hidden;
      margin: 8px 0;
    }

    .tile-track {
      position: relative;
      width: 290px;
      height: 90px;
    }

    /* Tile Primitives */
    .tile {
      position: absolute;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 15px;
      font-weight: 700;
      color: #ffffff;
      border-radius: 4px;
      box-shadow: 0 2px 4px rgba(0,0,0,0.08);
      transition: transform 0.6s cubic-bezier(0.34, 1.3, 0.64, 1), opacity 0.3s;
    }
    .tile-x {
      width: 26px;
      height: 76px;
      background: #2563eb;
      top: 7px;
    }
    .tile-1 {
      width: 26px;
      height: 26px;
      background: #10b981;
      top: 32px;
    }

    /* Shift Arrow in Step 2 */
    .motion-arrow {
      position: absolute;
      top: -4px;
      left: 170px;
      width: 80px;
      height: 20px;
      display: flex;
      align-items: center;
      justify-content: center;
      color: #2563eb;
      font-size: 18px;
      font-weight: 900;
      opacity: 0;
      transition: opacity 0.3s ease;
      pointer-events: none;
    }
    .arrow-arc {
      position: absolute;
      width: 70px;
      height: 18px;
      border: 2px dashed #2563eb;
      border-bottom: none;
      border-radius: 50px 50px 0 0;
      top: 2px;
    }
    .arrow-head {
      position: absolute;
      left: -2px;
      top: 8px;
      font-size: 12px;
      transform: rotate(-70deg);
    }

    /* Status & Badge */
    .bottom-panel {
      height: 38px;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .badge {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      padding: 6px 14px;
      background: #dcfce7;
      color: #15803d;
      border: 1px solid #86efac;
      border-radius: 20px;
      font-size: 14px;
      font-weight: 700;
      opacity: 0;
      transform: translateY(6px);
      transition: opacity 0.4s ease, transform 0.4s ease;
    }
    .badge.visible {
      opacity: 1;
      transform: translateY(0);
    }

    /* Key Group Labels */
    .group-label {
      position: absolute;
      bottom: -4px;
      font-size: 12px;
      font-weight: 700;
      opacity: 0;
      transition: opacity 0.3s ease;
    }
    .label-4x {
      left: 36px;
      color: #2563eb;
    }
    .label-2 {
      left: 168px;
      color: #10b981;
    }
  </style>
</head>
<body>

  
  <div class="controls">
    <button class="step-btn active" id="btn0" onclick="setStep(0)">1. Model</button>
    <button class="step-btn" id="btn1" onclick="setStep(1)">2. Group</button>
    <button class="step-btn" id="btn2" onclick="setStep(2)">3. Simplify</button>
    <button class="play-btn" id="playBtn" onclick="togglePlay()" aria-label="Play / Pause">▶</button>
  </div>

  
  <div class="expression-box" id="exprBox">
    
  </div>

  
  <div class="stage">
    <div class="tile-track">
      
      <div class="tile tile-x" id="x1" style="left: 15px;">x</div>
      <div class="tile tile-x" id="x2" style="left: 45px;">x</div>
      <div class="tile tile-x" id="x3" style="left: 75px;">x</div>

      
      <div class="tile tile-1" id="u1" style="left: 130px;">1</div>
      <div class="tile tile-1" id="u2" style="left: 160px;">1</div>

      
      <div class="tile tile-x" id="x4" style="left: 215px;">x</div>

      
      <div class="group-label label-4x" id="lbl4x">4x</div>
      <div class="group-label label-2" id="lbl2">+ 2</div>

      
      <div class="motion-arrow" id="motionArrow">
        <div class="arrow-arc"></div>
        <span class="arrow-head">◀</span>
      </div>
    </div>
  </div>

  
  <div class="bottom-panel">
    <div class="badge" id="equivBadge">
      <span>✓</span> Equivalent!
    </div>
  </div>

  <script>
    let step = 0;
    let timer = null;
    let playing = false;

    const expressions = [
      '<span class="term-x">3x</span> <span class="term-op">+</span> <span class="term-const">2</span> <span class="term-op">+</span> <span class="term-x">x</span>',
      '<span class="term-x">3x</span> <span class="term-op">+</span> <span class="term-x">x</span> <span class="term-op">+</span> <span class="term-const">2</span>',
      '<span class="term-x">4x</span> <span class="term-op">+</span> <span class="term-const">2</span>'
    ];

    function updateView() {
      // Step buttons
      for (let i = 0; i < 3; i++) {
        document.getElementById(`btn${i}`).classList.toggle('active', i === step);
      }

      // Expression
      document.getElementById('exprBox').innerHTML = expressions[step];

      const x4 = document.getElementById('x4');
      const u1 = document.getElementById('u1');
      const u2 = document.getElementById('u2');
      const arrow = document.getElementById('motionArrow');
      const badge = document.getElementById('equivBadge');
      const lbl4x = document.getElementById('lbl4x');
      const lbl2 = document.getElementById('lbl2');

      if (step === 0) {
        // Initial spread layout
        x4.style.transform = 'translateX(0px)';
        u1.style.transform = 'translateX(0px)';
        u2.style.transform = 'translateX(0px)';
        arrow.style.opacity = '0';
        badge.classList.remove('visible');
        lbl4x.style.opacity = '0';
        lbl2.style.opacity = '0';
      } else if (step === 1) {
        // Lone x bar sliding over
        x4.style.transform = 'translateX(-110px)';
        u1.style.transform = 'translateX(35px)';
        u2.style.transform = 'translateX(35px)';
        arrow.style.opacity = '1';
        badge.classList.remove('visible');
        lbl4x.style.opacity = '0';
        lbl2.style.opacity = '0';
      } else if (step === 2) {
        // Fully combined & labeled
        x4.style.transform = 'translateX(-110px)';
        u1.style.transform = 'translateX(35px)';
        u2.style.transform = 'translateX(35px)';
        arrow.style.opacity = '0';
        badge.classList.add('visible');
        lbl4x.style.opacity = '1';
        lbl2.style.opacity = '1';
      }
    }

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

    function togglePlay() {
      playing = !playing;
      document.getElementById('playBtn').textContent = playing ? '⏸' : '▶';
      if (playing) {
        runAutoPlay();
      } else {
        clearInterval(timer);
      }
    }

    function runAutoPlay() {
      clearInterval(timer);
      timer = setInterval(() => {
        step = (step + 1) % 3;
        updateView();
      }, 3200);
    }

    // Initialize
    updateView();
  </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; }
    body {
      width: 100%;
      min-height: 100%;
      background: #ffffff;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 12px;
    }

    .diagram {
      width: 100%;
      max-width: 620px;
      display: flex;
      flex-direction: column;
      gap: 14px;
    }

    .comparison {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
      position: relative;
    }

    .side {
      flex: 1;
      display: flex;
      flex-direction: column;
      align-items: center;
      background: #f8fafc;
      border-radius: 12px;
      padding: 12px 8px;
      border: 1px solid #e2e8f0;
    }

    .expr-title {
      font-size: 18px;
      font-weight: 700;
      margin-bottom: 10px;
      color: #0f172a;
    }

    .tiles-container {
      display: flex;
      flex-direction: column;
      gap: 8px;
      width: 100%;
      align-items: center;
    }

    .tile-row {
      display: flex;
      align-items: center;
      gap: 4px;
      background: #ffffff;
      padding: 6px;
      border-radius: 8px;
      border: 1px dashed #cbd5e1;
      width: 100%;
      max-width: 230px;
      justify-content: center;
    }

    .tile-x {
      background: #3b82f6;
      color: #ffffff;
      font-weight: 700;
      font-size: 14px;
      width: 36px;
      height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
      border-radius: 4px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }

    .tile-1 {
      background: #22c55e;
      color: #ffffff;
      font-weight: 700;
      font-size: 13px;
      width: 26px;
      height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
      border-radius: 4px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }

    .tile-1.missing {
      background: #f1f5f9;
      color: #ef4444;
      border: 2px dashed #f87171;
      box-shadow: none;
    }

    .summary-tag {
      margin-top: 10px;
      font-size: 13px;
      font-weight: 600;
      padding: 3px 8px;
      border-radius: 6px;
      background: #e2e8f0;
      color: #334155;
    }

    .not-equal-sign {
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 32px;
      font-weight: 900;
      color: #ef4444;
      width: 36px;
      height: 36px;
      flex-shrink: 0;
    }

    .callout {
      background: #fef2f2;
      border: 1px solid #fecaca;
      border-radius: 8px;
      padding: 8px 12px;
      text-align: center;
      font-size: 14px;
      font-weight: 600;
      color: #b91c1c;
    }

    .interactive-btn {
      align-self: center;
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
    }

    .interactive-btn:active {
      background: #f1f5f9;
    }

    @media (max-width: 460px) {
      .tile-x { width: 28px; height: 28px; font-size: 12px; }
      .tile-1 { width: 20px; height: 28px; font-size: 11px; }
      .tile-row { padding: 4px; gap: 3px; }
      .expr-title { font-size: 16px; margin-bottom: 6px; }
      .summary-tag { font-size: 12px; }
      .not-equal-sign { font-size: 26px; width: 24px; }
      .callout { font-size: 13px; padding: 6px 8px; }
    }
  </style>
</head>
<body>
  <div class="diagram">
    <div class="comparison">
      
      <div class="side">
        <div class="expr-title">2(x + 4)</div>
        <div class="tiles-container">
          <div class="tile-row">
            <div class="tile-x">x</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
          </div>
          <div class="tile-row">
            <div class="tile-x">x</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
          </div>
        </div>
        <div class="summary-tag">2x + 8 units</div>
      </div>

      
      <div class="not-equal-sign">≠</div>

      
      <div class="side">
        <div class="expr-title">2x + 4</div>
        <div class="tiles-container">
          <div class="tile-row">
            <div class="tile-x">x</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
            <div class="tile-1">1</div>
          </div>
          <div class="tile-row">
            <div class="tile-x">x</div>
            <div class="tile-1 missing" id="m1">?</div>
            <div class="tile-1 missing" id="m2">?</div>
            <div class="tile-1 missing" id="m3">?</div>
            <div class="tile-1 missing" id="m4">?</div>
          </div>
        </div>
        <div class="summary-tag">2x + 4 units</div>
      </div>
    </div>

    
    <div class="callout" id="calloutText">
      Missing 4 unit tiles on the right (8 vs 4)
    </div>

    
    <button class="interactive-btn" id="toggleBtn" onclick="toggleMissing()">
      <span>✦ Highlight difference</span>
    </button>
  </div>

  <script>
    let highlighted = true;
    function toggleMissing() {
      highlighted = !highlighted;
      const ids = ['m1', 'm2', 'm3', 'm4'];
      ids.forEach(id => {
        const el = document.getElementById(id);
        if (highlighted) {
          el.style.background = '#f1f5f9';
          el.style.border = '2px dashed #f87171';
          el.textContent = '?';
        } else {
          el.style.background = 'transparent';
          el.style.border = '1px solid transparent';
          el.textContent = '';
        }
      });
      document.getElementById('toggleBtn').querySelector('span').textContent = 
        highlighted ? '✦ Hide highlights' : '✦ Show missing tiles';
    }
  </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;
    }
    body {
      background-color: #f8f9fa;
      color: #1e2945;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
      padding: 16px;
    }
    .subtitle {
      font-size: 15px;
      font-weight: 600;
      color: #475569;
      margin-bottom: 24px;
      text-align: center;
      background: #ffffff;
      padding: 6px 16px;
      border-radius: 20px;
      border: 1px solid #cbd5e1;
    }
    .tiles-wrapper {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      justify-content: center;
      gap: 32px;
      width: 100%;
      max-width: 540px;
    }
    .tile-group {
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }
    .dimension-top {
      font-size: 14px;
      font-weight: 700;
      color: #64748b;
      margin-bottom: 6px;
    }
    .tile-row {
      display: flex;
      align-items: center;
    }
    .dimension-left {
      font-size: 14px;
      font-weight: 700;
      color: #64748b;
      margin-right: 8px;
    }
    .tile {
      display: flex;
      align-items: center;
      justify-content: center;
      font-weight: 700;
      color: #ffffff;
      border-radius: 6px;
      border: 2px solid rgba(0, 0, 0, 0.1);
      box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
      transition: transform 0.2s ease, box-shadow 0.2s ease;
      cursor: default;
    }
    .unit-tile {
      width: 72px;
      height: 72px;
      background-color: #22c55e;
      font-size: 15px;
    }
    .x-tile {
      width: 180px;
      height: 72px;
      background-color: #3b82f6;
      font-size: 15px;
    }
    .label {
      font-size: 14px;
      font-weight: 600;
      color: #1e2945;
      margin-top: 10px;
      text-align: center;
    }
    @media (max-width: 400px) {
      .tiles-wrapper {
        gap: 20px;
      }
      .x-tile {
        width: 150px;
      }
    }
  </style>
</head>
<body>

  <div class="subtitle">
    Area of 1 &times; 1 = 1 &nbsp;&bull;&nbsp; Area of 1 &times; <em>x</em> = <em>x</em>
  </div>

  <div class="tiles-wrapper">
    
    <div class="tile-group">
      <span class="dimension-top">1</span>
      <div class="tile-row">
        <span class="dimension-left">1</span>
        <div class="tile unit-tile">1</div>
      </div>
      <span class="label">Unit Tile = 1</span>
    </div>

    
    <div class="tile-group">
      <span class="dimension-top"><em>x</em></span>
      <div class="tile-row">
        <span class="dimension-left">1</span>
        <div class="tile x-tile"><em>x</em></div>
      </div>
      <span class="label"><em>x</em>-Tile = <em>x</em></span>
    </div>
  </div>

</body>
</html>

111.26(b)(7)(C)

Aligned learning resources

Related diagrams