<!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;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .stepper-nav {
      display: flex;
      gap: 6px;
      margin-bottom: 14px;
      width: 100%;
      max-width: 480px;
      justify-content: center;
    }
    .step-btn {
      flex: 1;
      padding: 6px 10px;
      font-size: 13px;
      font-weight: 600;
      border: 1px solid #e2e8f0;
      background: #f8fafc;
      color: #64748b;
      border-radius: 20px;
      cursor: pointer;
      text-align: center;
      transition: all 0.25s ease;
    }
    .step-btn.active {
      background: #22b7ff;
      color: #ffffff;
      border-color: #22b7ff;
    }

    .stage {
      width: 100%;
      max-width: 480px;
      position: relative;
      padding: 32px 8px 12px;
    }

    /* Extras Bracket */
    .extras-bracket {
      position: absolute;
      top: 0;
      right: 4%;
      width: 36%;
      text-align: center;
      opacity: 0;
      transform: translateY(4px);
      transition: all 0.3s ease;
      pointer-events: none;
    }
    .extras-bracket.show {
      opacity: 1;
      transform: translateY(0);
    }
    .bracket-label {
      background: #ffedd5;
      color: #c2410c;
      border: 1.5px solid #fdba74;
      font-size: 12px;
      font-weight: 700;
      padding: 2px 8px;
      border-radius: 12px;
      display: inline-block;
      margin-bottom: 4px;
      white-space: nowrap;
    }
    .bracket-svg {
      width: 100%;
      height: 12px;
      display: block;
    }

    /* Grid Layout */
    .matching-grid {
      display: grid;
      grid-template-columns: repeat(5, 1fr);
      gap: 8px;
      align-items: center;
      justify-items: center;
    }

    .item-card {
      width: 100%;
      aspect-ratio: 1;
      max-width: 68px;
      border-radius: 14px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 28px;
      position: relative;
      transition: all 0.3s ease;
    }

    .leaf-card {
      background: #f0fdf4;
      border: 1.5px solid #bbf7d0;
    }
    .leaf-card.extra {
      background: #fff7ed;
      border: 1.5px dashed #fb923c;
    }

    .acorn-card {
      background: #fdf6ec;
      border: 1.5px solid #fed7aa;
    }
    .empty-card {
      background: #f8fafc;
      border: 1.5px dashed #cbd5e1;
      opacity: 0.5;
    }

    /* Matching Link Lines */
    .connector {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      height: 38px;
      width: 100%;
    }
    .link-line {
      width: 3px;
      height: 0;
      background: #94a3b8;
      border-radius: 2px;
      transition: height 0.35s ease;
      position: relative;
    }
    .link-line.active {
      height: 28px;
      background: #10b981;
    }
    .link-line.active::after {
      content: '✓';
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      background: #10b981;
      color: #fff;
      font-size: 10px;
      font-weight: bold;
      width: 15px;
      height: 15px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .link-missing {
      font-size: 16px;
      color: #94a3b8;
      opacity: 0;
      transition: opacity 0.3s ease;
    }
    .link-missing.show {
      opacity: 0.4;
    }

    /* Bottom Summary */
    .summary-bar {
      display: flex;
      gap: 8px;
      width: 100%;
      max-width: 480px;
      margin-top: 14px;
    }
    .summary-pill {
      flex: 1;
      padding: 8px 10px;
      border-radius: 10px;
      font-size: 13px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      text-align: center;
    }
    .pill-more {
      background: #ecfdf5;
      color: #047857;
      border: 1px solid #a7f3d0;
    }
    .pill-fewer {
      background: #fffbeb;
      color: #b45309;
      border: 1px solid #fde68a;
    }

    @media (max-width: 400px) {
      .item-card { font-size: 24px; }
      .bracket-label { font-size: 10px; padding: 1px 6px; }
      .step-btn { font-size: 11px; padding: 5px 6px; }
      .summary-pill { font-size: 12px; }
    }
  </style>
</head>
<body>

  
  <div class="stepper-nav">
    <button class="step-btn active" onclick="setStep(0)">1. Line Up</button>
    <button class="step-btn" onclick="setStep(1)">2. Match Pairs</button>
    <button class="step-btn" onclick="setStep(2)">3. Find Extras</button>
  </div>

  <div class="stage">
    
    <div id="bracket" class="extras-bracket">
      <span class="bracket-label">2 Extras!</span>
      <svg class="bracket-svg" viewBox="0 0 100 12" preserveAspectRatio="none">
        <path d="M 4 10 Q 50 12 50 2 Q 50 12 96 10" fill="none" stroke="#f97316" stroke-width="2" stroke-linecap="round"/>
      </svg>
    </div>

    <div class="matching-grid">
      
      <div class="item-card leaf-card">🍃</div>
      <div class="item-card leaf-card">🍃</div>
      <div class="item-card leaf-card">🍃</div>
      <div id="leaf4" class="item-card leaf-card">🍃</div>
      <div id="leaf5" class="item-card leaf-card">🍃</div>

      
      <div class="connector"><div class="link-line"></div></div>
      <div class="connector"><div class="link-line"></div></div>
      <div class="connector"><div class="link-line"></div></div>
      <div class="connector"><div class="link-missing">✕</div></div>
      <div class="connector"><div class="link-missing">✕</div></div>

      
      <div class="item-card acorn-card">🌰</div>
      <div class="item-card acorn-card">🌰</div>
      <div class="item-card acorn-card">🌰</div>
      <div class="item-card empty-card"></div>
      <div class="item-card empty-card"></div>
    </div>
  </div>

  
  <div class="summary-bar">
    <div class="summary-pill pill-more">
      <span>🍃</span> More leaves
    </div>
    <div class="summary-pill pill-fewer">
      <span>🌰</span> Fewer acorns
    </div>
  </div>

  <script>
    let currentStep = 0;
    const buttons = document.querySelectorAll('.step-btn');
    const lines = document.querySelectorAll('.link-line');
    const missings = document.querySelectorAll('.link-missing');
    const bracket = document.getElementById('bracket');
    const leaf4 = document.getElementById('leaf4');
    const leaf5 = document.getElementById('leaf5');

    function setStep(step) {
      currentStep = step;
      buttons.forEach((b, i) => b.classList.toggle('active', i === step));

      // Step 1: Just lined up
      // Step 2: Matched pairs linked
      // Step 3: Extras highlighted
      lines.forEach(l => l.classList.toggle('active', step >= 1));
      missings.forEach(m => m.classList.toggle('show', step >= 1));

      const isStep2 = (step === 2);
      bracket.classList.toggle('show', isStep2);
      leaf4.classList.toggle('extra', isStep2);
      leaf5.classList.toggle('extra', isStep2);
    }

    // Auto-advance slowly for pedagogical clarity
    let autoTimer = setInterval(() => {
      setStep((currentStep + 1) % 3);
    }, 3800);

    buttons.forEach((btn) => {
      btn.addEventListener('click', () => {
        clearInterval(autoTimer);
      });
    });
  </script>
</body>
</html>

Comparing Two Sets Using Matching Strategies

<!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: #f8fafc;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .grid-container {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 14px;
      width: 100%;
      max-width: 620px;
    }

    @media (max-width: 480px) {
      .grid-container {
        grid-template-columns: 1fr;
        gap: 12px;
      }
    }

    .panel {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 16px;
      padding: 14px 12px 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }

    .panel.success {
      border-color: #38bdf8;
      background: #f0f9ff;
    }

    .header-tag {
      font-size: 15px;
      font-weight: 800;
      padding: 4px 12px;
      border-radius: 20px;
      margin-bottom: 12px;
      display: inline-flex;
      align-items: center;
      gap: 5px;
    }

    .tag-tricky {
      background: #fef3c7;
      color: #b45309;
    }

    .tag-aligned {
      background: #dbeafe;
      color: #1d4ed8;
    }

    .stage {
      width: 100%;
      height: 150px;
      position: relative;
      background: #ffffff;
      border-radius: 12px;
      border: 1px dashed #cbd5e1;
      display: flex;
      flex-direction: column;
      justify-content: space-around;
      padding: 10px 14px;
    }

    .berry-row {
      display: flex;
      align-items: center;
      width: 100%;
      height: 48px;
      position: relative;
    }

    /* Left panel layouts */
    .spread-wide {
      justify-content: space-between;
    }

    .packed-tight {
      justify-content: flex-start;
      gap: 10px;
      padding-left: 8px;
    }

    /* Right panel grid layout */
    .aligned-grid {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      width: 100%;
      height: 100%;
      position: relative;
    }

    .slot {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      height: 100%;
      position: relative;
    }

    .match-line {
      position: absolute;
      top: 36px;
      bottom: 36px;
      width: 2px;
      border-left: 2px dashed #94a3b8;
      z-index: 1;
    }

    .match-line.matched {
      border-left: 2px dashed #38bdf8;
    }

    /* Berries */
    .berry {
      width: 36px;
      height: 36px;
      border-radius: 50%;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 13px;
      font-weight: 800;
      color: #ffffff;
      box-shadow: 0 3px 6px rgba(0,0,0,0.12);
      z-index: 2;
      position: relative;
      user-select: none;
    }

    .berry-red {
      background: radial-gradient(circle at 35% 35%, #ff5252, #dc2626);
    }

    .berry-blue {
      background: radial-gradient(circle at 35% 35%, #60a5fa, #2563eb);
    }

    .empty-slot {
      width: 34px;
      height: 34px;
      border-radius: 50%;
      border: 2px dashed #cbd5e1;
      display: flex;
      align-items: center;
      justify-content: center;
      color: #94a3b8;
      font-size: 15px;
      z-index: 2;
    }

    .extra-tag {
      position: absolute;
      bottom: -8px;
      background: #2563eb;
      color: #ffffff;
      font-size: 11px;
      font-weight: 700;
      padding: 1px 6px;
      border-radius: 8px;
      white-space: nowrap;
    }

    .footer-result {
      margin-top: 10px;
      font-size: 13px;
      font-weight: 700;
      text-align: center;
    }

    .text-warn { color: #b45309; }
    .text-success { color: #16a34a; }
  </style>
</head>
<body>

  <div class="grid-container">

    
    <div class="panel">
      <div class="header-tag tag-tricky">Tricky!</div>
      
      <div class="stage">
        
        <div class="berry-row spread-wide">
          <div class="berry berry-red">1</div>
          <div class="berry berry-red">2</div>
          <div class="berry berry-red">3</div>
        </div>

        
        <div class="berry-row packed-tight">
          <div class="berry berry-blue">1</div>
          <div class="berry berry-blue">2</div>
          <div class="berry berry-blue">3</div>
          <div class="berry berry-blue">4</div>
        </div>
      </div>

      <div class="footer-result text-warn">Looks longer! (Optical Illusion)</div>
    </div>

    
    <div class="panel success">
      <div class="header-tag tag-aligned">Parallel Rows!</div>
      
      <div class="stage">
        <div class="aligned-grid">
          
          <div class="slot">
            <div class="berry berry-red">1</div>
            <div class="match-line matched"></div>
            <div class="berry berry-blue">1</div>
          </div>

          
          <div class="slot">
            <div class="berry berry-red">2</div>
            <div class="match-line matched"></div>
            <div class="berry berry-blue">2</div>
          </div>

          
          <div class="slot">
            <div class="berry berry-red">3</div>
            <div class="match-line matched"></div>
            <div class="berry berry-blue">3</div>
          </div>

          
          <div class="slot">
            <div class="empty-slot">✕</div>
            <div class="match-line"></div>
            <div class="berry berry-blue">4</div>
            <div class="extra-tag">+1 Extra</div>
          </div>
        </div>
      </div>

      <div class="footer-result text-success">4 is more than 3! ✓</div>
    </div>

  </div>

</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>Matching Strategies Progression</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    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: 12px 8px;
    }

    .stepper-nav {
      display: flex;
      gap: 8px;
      margin-bottom: 12px;
      align-items: center;
    }

    .nav-btn {
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      border: 1px solid #e2e8f0;
      border-radius: 20px;
      background: #f8fafc;
      color: #64748b;
      cursor: pointer;
      box-shadow: none;
      transition: all 0.25s ease;
    }
    .nav-btn.active {
      background: #e0f2fe;
      color: #0284c7;
      border-color: #7dd3fc;
      box-shadow: 0 0 0 2px rgba(14, 165, 233, 0.2);
    }

    .play-btn {
      padding: 6px 10px;
      font-size: 13px;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      background: #ffffff;
      color: #334155;
      cursor: pointer;
    }

    .grid-container {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
      width: 100%;
      max-width: 640px;
      align-items: stretch;
    }

    @media (max-width: 520px) {
      .grid-container {
        grid-template-columns: 1fr;
        gap: 12px;
      }
      .arrow-divider {
        transform: rotate(90deg);
        margin: 2px 0;
      }
    }

    .step-card {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 14px;
      padding: 12px 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      transition: all 0.3s ease;
      position: relative;
    }

    .step-card.active-card {
      border-color: #38bdf8;
      box-shadow: 0 4px 14px rgba(56, 189, 248, 0.18);
      transform: translateY(-2px);
    }

    .step-title {
      font-size: 13.5px;
      font-weight: 700;
      color: #334155;
      margin-bottom: 8px;
      text-align: center;
    }

    .visual-area {
      width: 100%;
      height: 140px;
      background: #f8fafc;
      border-radius: 10px;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      overflow: hidden;
    }

    /* STEP 1: Concrete */
    .concrete-container {
      display: flex;
      flex-direction: column;
      gap: 16px;
      align-items: center;
      width: 100%;
    }
    .object-row {
      display: flex;
      gap: 18px;
      align-items: center;
      justify-content: center;
    }
    .hand-touch {
      position: absolute;
      font-size: 20px;
      opacity: 0.9;
      animation: nudge 2.4s ease-in-out infinite;
    }
    .left-hand { left: 8px; }
    .right-hand { right: 8px; }

    @keyframes nudge {
      0%, 100% { transform: scale(1); }
      50% { transform: scale(1.08) translateX(2px); }
    }

    .pinecone {
      width: 28px;
      height: 34px;
      background: #8b5a2b;
      border-radius: 50% 50% 40% 40%;
      position: relative;
      box-shadow: inset 0 -3px 0 rgba(0,0,0,0.2), inset 0 2px 0 rgba(255,255,255,0.2);
    }
    .pinecone::before {
      content: "✦";
      position: absolute;
      color: #b7793d;
      font-size: 14px;
      left: 7px;
      top: 6px;
    }

    .acorn {
      width: 26px;
      height: 30px;
      background: #a06235;
      border-radius: 40% 40% 50% 50%;
      position: relative;
      box-shadow: inset 0 -2px 0 rgba(0,0,0,0.2);
    }
    .acorn::before {
      content: "";
      position: absolute;
      top: -4px;
      left: 3px;
      width: 20px;
      height: 10px;
      background: #5c3417;
      border-radius: 8px 8px 3px 3px;
    }

    /* STEP 2: Pictorial */
    .pictorial-svg {
      width: 100%;
      height: 100%;
    }

    /* STEP 3: Abstract / Math Tools */
    .cubes-container {
      display: flex;
      gap: 20px;
      align-items: center;
      justify-content: center;
    }
    .cube-tower {
      display: flex;
      flex-direction: column;
      gap: 3px;
    }
    .cube {
      width: 32px;
      height: 26px;
      border-radius: 4px;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }
    .cube::after {
      content: "";
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: rgba(255,255,255,0.75);
    }
    .cube-blue {
      background: #0284c7;
      border-bottom: 2px solid #0369a1;
    }
    .cube-orange {
      background: #f97316;
      border-bottom: 2px solid #c2410c;
    }

    .match-guideline {
      stroke: #94a3b8;
      stroke-dasharray: 4 3;
      stroke-width: 1.5;
    }

    .arrow-icon {
      color: #94a3b8;
      font-size: 16px;
      display: none;
    }
  </style>
</head>
<body>

  <div class="stepper-nav">
    <button class="nav-btn active" data-step="0">1. Real Objects</button>
    <button class="nav-btn" data-step="1">2. Pictures & Lines</button>
    <button class="nav-btn" data-step="2">3. Math Tools</button>
    <button class="play-btn" id="playBtn" title="Play / Pause">▶</button>
  </div>

  <div class="grid-container">
    
    <div class="step-card active-card" id="card-0">
      <div class="step-title">1. Real Objects</div>
      <div class="visual-area">
        <span class="hand-touch left-hand">🫲</span>
        <div class="concrete-container">
          <div class="object-row">
            <div class="pinecone" title="Pinecone"></div>
            <div class="pinecone" title="Pinecone"></div>
            <div class="pinecone" title="Pinecone"></div>
          </div>
          <div class="object-row">
            <div class="acorn" title="Acorn"></div>
            <div class="acorn" title="Acorn"></div>
            <div class="acorn" title="Acorn"></div>
          </div>
        </div>
        <span class="hand-touch right-hand">🫱</span>
      </div>
    </div>

    
    <div class="step-card" id="card-1">
      <div class="step-title">2. Pictures & Lines</div>
      <div class="visual-area">
        <svg class="pictorial-svg" viewBox="0 0 160 140">
          
          <g transform="translate(25, 20)">
            <ellipse cx="15" cy="15" rx="10" ry="13" fill="#b7793d" />
            <circle cx="15" cy="15" r="4" fill="#8b5a2b" opacity="0.6" />
          </g>
          <g transform="translate(70, 20)">
            <ellipse cx="15" cy="15" rx="10" ry="13" fill="#b7793d" />
            <circle cx="15" cy="15" r="4" fill="#8b5a2b" opacity="0.6" />
          </g>
          <g transform="translate(115, 20)">
            <ellipse cx="15" cy="15" rx="10" ry="13" fill="#b7793d" />
            <circle cx="15" cy="15" r="4" fill="#8b5a2b" opacity="0.6" />
          </g>

          
          <path d="M 40, 52 C 40, 70 40, 70 40, 88" stroke="#3b82f6" stroke-width="2.5" stroke-dasharray="4 3" stroke-linecap="round" fill="none" />
          <path d="M 85, 52 C 85, 70 85, 70 85, 88" stroke="#3b82f6" stroke-width="2.5" stroke-dasharray="4 3" stroke-linecap="round" fill="none" />
          <path d="M 130, 52 C 130, 70 130, 70 130, 88" stroke="#3b82f6" stroke-width="2.5" stroke-dasharray="4 3" stroke-linecap="round" fill="none" />

          
          <g transform="translate(25, 90)">
            <ellipse cx="15" cy="16" rx="9" ry="11" fill="#c28859" />
            <rect x="7" y="5" width="16" height="8" rx="4" fill="#6d4323" />
          </g>
          <g transform="translate(70, 90)">
            <ellipse cx="15" cy="16" rx="9" ry="11" fill="#c28859" />
            <rect x="7" y="5" width="16" height="8" rx="4" fill="#6d4323" />
          </g>
          <g transform="translate(115, 90)">
            <ellipse cx="15" cy="16" rx="9" ry="11" fill="#c28859" />
            <rect x="7" y="5" width="16" height="8" rx="4" fill="#6d4323" />
          </g>
        </svg>
      </div>
    </div>

    
    <div class="step-card" id="card-2">
      <div class="step-title">3. Math Tools</div>
      <div class="visual-area">
        <svg style="position:absolute; inset:0; width:100%; height:100%; pointer-events:none;" viewBox="0 0 160 140">
          <line x1="38" y1="36" x2="122" y2="36" class="match-guideline" />
          <line x1="38" y1="67" x2="122" y2="67" class="match-guideline" />
          <line x1="38" y1="98" x2="122" y2="98" class="match-guideline" />
        </svg>
        <div class="cubes-container">
          
          <div class="cube-tower">
            <div class="cube cube-blue"></div>
            <div class="cube cube-blue"></div>
            <div class="cube cube-blue"></div>
          </div>
          
          <div class="cube-tower">
            <div class="cube cube-orange"></div>
            <div class="cube cube-orange"></div>
            <div class="cube cube-orange"></div>
          </div>
        </div>
      </div>
    </div>
  </div>

  <script src="{{VENDOR_CDN}}/classace-diagram.js"></script>
  <script>
    const buttons = document.querySelectorAll('.nav-btn');
    const cards = [document.getElementById('card-0'), document.getElementById('card-1'), document.getElementById('card-2')];
    const playBtn = document.getElementById('playBtn');

    let currentStep = 0;
    let isPlaying = true;
    let timer = null;

    function setStep(idx) {
      currentStep = idx;
      buttons.forEach((btn, i) => {
        btn.classList.toggle('active', i === idx);
      });
      cards.forEach((card, i) => {
        card.classList.toggle('active-card', i === idx);
      });
    }

    function startTimer() {
      if (timer) clearInterval(timer);
      timer = setInterval(() => {
        if (!isPlaying) return;
        setStep((currentStep + 1) % 3);
      }, 3200);
    }

    buttons.forEach((btn, i) => {
      btn.addEventListener('click', () => {
        setStep(i);
        isPlaying = false;
        playBtn.textContent = '▶';
        if (timer) clearInterval(timer);
      });
    });

    cards.forEach((card, i) => {
      card.addEventListener('click', () => {
        setStep(i);
        isPlaying = false;
        playBtn.textContent = '▶';
        if (timer) clearInterval(timer);
      });
      card.style.cursor = 'pointer';
    });

    playBtn.addEventListener('click', () => {
      isPlaying = !isPlaying;
      playBtn.textContent = isPlaying ? '⏸' : '▶';
      if (isPlaying) {
        startTimer();
      } else {
        if (timer) clearInterval(timer);
      }
    });

    startTimer();
  </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;
      user-select: none;
      -webkit-user-select: none;
    }

    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: space-between;
      padding: 16px 12px;
    }

    .main-grid {
      display: flex;
      justify-content: space-around;
      align-items: center;
      width: 100%;
      max-width: 480px;
      flex: 1;
      gap: 8px;
    }

    .match-col {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      flex: 1;
      padding: 8px 4px;
      border-radius: 16px;
      background: #f8fafc;
      border: 2px solid #edf2f7;
      transition: background 0.3s ease, border-color 0.3s ease, transform 0.3s ease;
      cursor: pointer;
    }

    .match-col.matched {
      background: #f0fdf4;
      border-color: #86efac;
    }

    .item-card {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      width: 72px;
      height: 72px;
      background: #ffffff;
      border-radius: 14px;
      border: 1px solid #e2e8f0;
      box-shadow: 0 2px 6px rgba(0, 0, 0, 0.04);
      font-size: 40px;
      line-height: 1;
    }

    .connector-line {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      height: 60px;
      width: 24px;
      position: relative;
    }

    .line-track {
      width: 4px;
      height: 100%;
      border-left: 3px dashed #cbd5e1;
      transition: border-color 0.3s ease;
    }

    .match-col.matched .line-track {
      border-left: 3px dashed #22c55e;
    }

    .check-bubble {
      width: 28px;
      height: 28px;
      border-radius: 50%;
      background: #e2e8f0;
      color: #ffffff;
      font-size: 16px;
      font-weight: 800;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-top: 8px;
      transition: background 0.3s ease, transform 0.3s ease;
    }

    .match-col.matched .check-bubble {
      background: #22c55e;
      transform: scale(1.1);
    }

    .badge-wrap {
      width: 100%;
      max-width: 480px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 10px;
      margin-top: 8px;
    }

    .badge-equal {
      background: #22c55e;
      color: #ffffff;
      font-size: 20px;
      font-weight: 800;
      padding: 10px 24px;
      border-radius: 30px;
      box-shadow: 0 4px 12px rgba(34, 197, 94, 0.25);
      display: flex;
      align-items: center;
      gap: 8px;
      letter-spacing: 0.2px;
      text-align: center;
      transition: opacity 0.3s ease, transform 0.3s ease;
    }

    .badge-equal.dimmed {
      opacity: 0.3;
      transform: scale(0.96);
    }

    .count-indicator {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 16px;
      font-size: 15px;
      font-weight: 700;
      color: #64748b;
    }

    .count-tag {
      background: #f1f5f9;
      padding: 4px 12px;
      border-radius: 20px;
      border: 1px solid #e2e8f0;
      color: #334155;
    }

    @media (max-width: 380px) {
      .item-card {
        width: 60px;
        height: 60px;
        font-size: 32px;
      }
      .connector-line {
        height: 44px;
      }
      .badge-equal {
        font-size: 17px;
        padding: 8px 18px;
      }
    }
  </style>
</head>
<body>

  <div class="count-indicator">
    <span class="count-tag">🧸 3 Bears</span>
    <span>=</span>
    <span class="count-tag">🍪 3 Cookies</span>
  </div>

  <div class="main-grid" id="grid">
    
    <div class="match-col matched" data-index="0" onclick="toggleMatch(0)">
      <div class="item-card">🧸</div>
      <div class="connector-line">
        <div class="line-track"></div>
      </div>
      <div class="item-card">🍪</div>
      <div class="check-bubble">✓</div>
    </div>

    
    <div class="match-col matched" data-index="1" onclick="toggleMatch(1)">
      <div class="item-card">🧸</div>
      <div class="connector-line">
        <div class="line-track"></div>
      </div>
      <div class="item-card">🍪</div>
      <div class="check-bubble">✓</div>
    </div>

    
    <div class="match-col matched" data-index="2" onclick="toggleMatch(2)">
      <div class="item-card">🧸</div>
      <div class="connector-line">
        <div class="line-track"></div>
      </div>
      <div class="item-card">🍪</div>
      <div class="check-bubble">✓</div>
    </div>
  </div>

  <div class="badge-wrap">
    <div class="badge-equal" id="statusBadge">
      <span>✦</span>
      <span>Equal (The Same!)</span>
      <span>✦</span>
    </div>
  </div>

  <script>
    const cols = document.querySelectorAll('.match-col');
    const badge = document.getElementById('statusBadge');

    function toggleMatch(idx) {
      cols[idx].classList.toggle('matched');
      updateStatus();
    }

    function updateStatus() {
      const allMatched = Array.from(cols).every(col => col.classList.contains('matched'));
      if (allMatched) {
        badge.classList.remove('dimmed');
        badge.innerHTML = '<span>✦</span><span>Equal (The Same!)</span><span>✦</span>';
      } else {
        const matchedCount = Array.from(cols).filter(col => col.classList.contains('matched')).length;
        badge.classList.add('dimmed');
        badge.innerHTML = `<span>Tap to match all (${matchedCount}/3)</span>`;
      }
    }
  </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;
    }
    html, body {
      width: 100%;
      height: 100%;
      background: #ffffff;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      user-select: none;
      -webkit-user-select: none;
    }
    .diagram-svg {
      width: 100%;
      height: auto;
      max-height: 100%;
      display: block;
    }
    .tap-target {
      cursor: pointer;
      transition: transform 0.2s ease, opacity 0.2s ease;
    }
    .tap-target:hover {
      opacity: 0.9;
    }
    .thought-bubble {
      animation: gentle-float 3s ease-in-out infinite alternate;
      transform-origin: 365px 65px;
    }
    @keyframes gentle-float {
      0% { transform: translateY(0px); }
      100% { transform: translateY(-4px); }
    }
    .spotlight {
      animation: pulse-glow 2.5s ease-in-out infinite alternate;
    }
    @keyframes pulse-glow {
      0% { opacity: 0.55; transform: scale(0.98); transform-origin: 345px 115px; }
      100% { opacity: 0.85; transform: scale(1.03); transform-origin: 345px 115px; }
    }
    .match-line {
      stroke-dasharray: 6 5;
      animation: dash-flow 20s linear infinite;
    }
    @keyframes dash-flow {
      to { stroke-dashoffset: -100; }
    }
  </style>
</head>
<body>

  <svg class="diagram-svg" viewBox="0 0 440 330" aria-label="Comparing 4 teddy bears to 3 cookies using matching lines">
    <defs>
      
      <radialGradient id="spotlightGrad" cx="50%" cy="50%" r="50%">
        <stop offset="0%" stop-color="#fef08a" stop-opacity="1" />
        <stop offset="70%" stop-color="#fef08a" stop-opacity="0.6" />
        <stop offset="100%" stop-color="#fde047" stop-opacity="0" />
      </radialGradient>
      
      
      <filter id="softShadow" x="-10%" y="-10%" width="120%" height="120%">
        <feDropShadow dx="0" dy="2" stdDeviation="3" flood-opacity="0.08" />
      </filter>
    </defs>

    
    <g id="top-label">
      <rect x="70" y="12" width="300" height="34" rx="17" fill="#eff6ff" stroke="#bfdbfe" stroke-width="1.5" />
      <text x="220" y="34" font-size="16" font-weight="800" fill="#1d4ed8" text-anchor="middle">
        More bears (1 left over)
      </text>
    </g>

    
    <ellipse class="spotlight" cx="345" cy="115" rx="46" ry="46" fill="url(#spotlightGrad)" />

    
    
    <g class="match-group">
      <line class="match-line" x1="75" y1="145" x2="75" y2="195" stroke="#16a34a" stroke-width="3.5" stroke-linecap="round" />
      <rect x="57" y="160" width="36" height="20" rx="10" fill="#dcfce7" stroke="#86efac" stroke-width="1" />
      <text x="75" y="174" font-size="11" font-weight="700" fill="#15803d" text-anchor="middle">✓ Match</text>
    </g>

    
    <g class="match-group">
      <line class="match-line" x1="165" y1="145" x2="165" y2="195" stroke="#16a34a" stroke-width="3.5" stroke-linecap="round" />
      <rect x="147" y="160" width="36" height="20" rx="10" fill="#dcfce7" stroke="#86efac" stroke-width="1" />
      <text x="165" y="174" font-size="11" font-weight="700" fill="#15803d" text-anchor="middle">✓ Match</text>
    </g>

    
    <g class="match-group">
      <line class="match-line" x1="255" y1="145" x2="255" y2="195" stroke="#16a34a" stroke-width="3.5" stroke-linecap="round" />
      <rect x="237" y="160" width="36" height="20" rx="10" fill="#dcfce7" stroke="#86efac" stroke-width="1" />
      <text x="255" y="174" font-size="11" font-weight="700" fill="#15803d" text-anchor="middle">✓ Match</text>
    </g>

    
    <g id="no-match-indicator">
      <line x1="345" y1="145" x2="345" y2="195" stroke="#cbd5e1" stroke-width="2" stroke-dasharray="3 3" stroke-linecap="round" />
      <rect x="323" y="160" width="44" height="20" rx="10" fill="#f1f5f9" stroke="#cbd5e1" stroke-width="1" />
      <text x="345" y="174" font-size="10" font-weight="700" fill="#64748b" text-anchor="middle">None</text>
    </g>

    
    
    <g class="tap-target" transform="translate(40, 80)">
      <circle cx="35" cy="35" r="32" fill="#f8fafc" stroke="#e2e8f0" stroke-width="2" filter="url(#softShadow)" />
      <text x="35" y="47" font-size="38" text-anchor="middle">🧸</text>
    </g>

    
    <g class="tap-target" transform="translate(130, 80)">
      <circle cx="35" cy="35" r="32" fill="#f8fafc" stroke="#e2e8f0" stroke-width="2" filter="url(#softShadow)" />
      <text x="35" y="47" font-size="38" text-anchor="middle">🧸</text>
    </g>

    
    <g class="tap-target" transform="translate(220, 80)">
      <circle cx="35" cy="35" r="32" fill="#f8fafc" stroke="#e2e8f0" stroke-width="2" filter="url(#softShadow)" />
      <text x="35" y="47" font-size="38" text-anchor="middle">🧸</text>
    </g>

    
    <g class="tap-target" transform="translate(310, 80)">
      <circle cx="35" cy="35" r="34" fill="#fef9c3" stroke="#facc15" stroke-width="2.5" filter="url(#softShadow)" />
      <text x="35" y="47" font-size="38" text-anchor="middle">🧸</text>
    </g>

    
    <g class="thought-bubble">
      <circle cx="360" cy="74" r="3" fill="#ffffff" stroke="#94a3b8" stroke-width="1.5" />
      <circle cx="367" cy="64" r="5" fill="#ffffff" stroke="#94a3b8" stroke-width="1.5" />
      
      <path d="M 368,48 
               C 363,48 358,43 360,37 
               C 356,32 360,24 367,24 
               C 371,18 382,18 387,23 
               C 394,22 399,28 397,35 
               C 402,40 398,48 391,48 Z" 
            fill="#ffffff" stroke="#94a3b8" stroke-width="1.5" />
      <text x="379" y="39" font-size="17" font-weight="900" fill="#ea580c" text-anchor="middle">?</text>
    </g>

    
    
    <g class="tap-target" transform="translate(40, 205)">
      <circle cx="35" cy="35" r="32" fill="#fff7ed" stroke="#fed7aa" stroke-width="2" filter="url(#softShadow)" />
      <text x="35" y="47" font-size="38" text-anchor="middle">🍪</text>
    </g>

    
    <g class="tap-target" transform="translate(130, 205)">
      <circle cx="35" cy="35" r="32" fill="#fff7ed" stroke="#fed7aa" stroke-width="2" filter="url(#softShadow)" />
      <text x="35" y="47" font-size="38" text-anchor="middle">🍪</text>
    </g>

    
    <g class="tap-target" transform="translate(220, 205)">
      <circle cx="35" cy="35" r="32" fill="#fff7ed" stroke="#fed7aa" stroke-width="2" filter="url(#softShadow)" />
      <text x="35" y="47" font-size="38" text-anchor="middle">🍪</text>
    </g>

    
    <g transform="translate(310, 205)">
      <circle cx="35" cy="35" r="32" fill="none" stroke="#cbd5e1" stroke-width="2" stroke-dasharray="5 4" />
      <circle cx="35" cy="35" r="24" fill="#f8fafc" opacity="0.6" />
      <text x="35" y="41" font-size="12" font-weight="700" fill="#94a3b8" text-anchor="middle">No</text>
      <text x="35" y="53" font-size="11" font-weight="700" fill="#94a3b8" text-anchor="middle">cookie</text>
    </g>

    
    <g id="bottom-label">
      <rect x="135" y="284" width="170" height="34" rx="17" fill="#fff7ed" stroke="#fed7aa" stroke-width="1.5" />
      <text x="220" y="306" font-size="16" font-weight="800" fill="#c2410c" text-anchor="middle">
        Fewer cookies
      </text>
    </g>
  </svg>

</body>
</html>

OGS.0.SEP.4

Aligned learning resources

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