<!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: 16px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
    }

    .header-nav {
      display: flex;
      gap: 8px;
      width: 100%;
      max-width: 520px;
      justify-content: center;
      margin-bottom: 12px;
    }

    .step-btn {
      flex: 1;
      padding: 8px 12px;
      font-size: 14px;
      font-weight: 600;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      background: #f8fafc;
      color: #64748b;
      cursor: pointer;
      text-align: center;
      transition: all 0.25s ease;
    }

    .step-btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.25);
    }

    .diagram-area {
      width: 100%;
      max-width: 520px;
      display: flex;
      flex-direction: column;
      gap: 16px;
      position: relative;
    }

    .bar-wrapper {
      position: relative;
      width: 100%;
    }

    .bar-label-top {
      display: flex;
      justify-content: space-between;
      align-items: flex-end;
      font-size: 14px;
      font-weight: 700;
      color: #0f172a;
      margin-bottom: 6px;
    }

    .total-bracket {
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      width: 100%;
      font-size: 15px;
      font-weight: 700;
      color: #0369a1;
      margin-bottom: 4px;
    }

    .bar-container {
      display: flex;
      height: 48px;
      border-radius: 8px;
      overflow: hidden;
      border: 2px solid #cbd5e1;
      background: #f1f5f9;
      position: relative;
    }

    /* Proportions: 8ft usable (84.2%), 1.5ft damaged (15.8%) */
    .bar-usable {
      width: 84.21%;
      background: #e0f2fe;
      border-right: 2px dashed #0284c7;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 14px;
      font-weight: 700;
      color: #0369a1;
      transition: all 0.3s ease;
    }

    .bar-damaged {
      width: 15.79%;
      background: repeating-linear-gradient(
        45deg,
        #fee2e2,
        #fee2e2 6px,
        #fca5a5 6px,
        #fca5a5 12px
      );
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 13px;
      font-weight: 700;
      color: #dc2626;
      position: relative;
      transition: opacity 0.3s ease;
    }

    .cross-mark {
      position: absolute;
      inset: 0;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 24px;
      color: #dc2626;
      font-weight: 900;
    }

    .arrow-divider {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 12px;
      padding: 4px 0;
      color: #64748b;
      font-size: 14px;
      font-weight: 600;
    }

    .arrow-icon {
      font-size: 18px;
      color: #0284c7;
    }

    .shelves-container {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 6px;
      width: 84.21%; /* Aligns exactly with the 8ft usable portion */
      transition: opacity 0.3s ease;
    }

    .shelf-piece {
      height: 48px;
      background: #ecfdf5;
      border: 2px solid #10b981;
      border-radius: 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      font-size: 14px;
      font-weight: 700;
      color: #047857;
      transition: transform 0.3s ease, box-shadow 0.3s ease;
    }

    .shelf-sub {
      font-size: 11px;
      font-weight: 600;
      color: #059669;
    }

    .calc-summary {
      width: 100%;
      max-width: 520px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 10px 14px;
      display: flex;
      justify-content: space-around;
      align-items: center;
      font-size: 14px;
      font-weight: 700;
    }

    .calc-step {
      display: flex;
      align-items: center;
      gap: 6px;
      color: #475569;
    }

    .calc-step.highlight {
      color: #0284c7;
    }

    .calc-badge {
      background: #e2e8f0;
      color: #334155;
      padding: 2px 7px;
      border-radius: 6px;
      font-size: 12px;
    }

    .calc-step.highlight .calc-badge {
      background: #0284c7;
      color: #ffffff;
    }
  </style>
</head>
<body>

  <div class="header-nav">
    <button class="step-btn active" onclick="setStep(0)">1. Cut Damaged</button>
    <button class="step-btn" onclick="setStep(1)">2. Divide Shelves</button>
  </div>

  <div class="diagram-area">
    
    <div class="bar-wrapper">
      <div class="total-bracket">
        Total: 9 ½ ft (19/2 ft)
      </div>
      <div class="bar-container">
        <div class="bar-usable" id="usableBar">
          8 ft Usable
        </div>
        <div class="bar-damaged" id="damagedBar">
          <span style="background: rgba(255,255,255,0.85); padding: 1px 4px; border-radius: 4px;">1 ½ ft</span>
          <div class="cross-mark" id="crossMark">✕</div>
        </div>
      </div>
    </div>

    
    <div class="arrow-divider">
      <span class="arrow-icon">↓</span>
      <span id="actionLabel">8 ft ÷ 4 = 2 ft per shelf</span>
      <span class="arrow-icon">↓</span>
    </div>

    
    <div class="bar-wrapper">
      <div class="shelves-container" id="shelvesContainer">
        <div class="shelf-piece">
          <span>2 ft</span>
          <span class="shelf-sub">Shelf 1</span>
        </div>
        <div class="shelf-piece">
          <span>2 ft</span>
          <span class="shelf-sub">Shelf 2</span>
        </div>
        <div class="shelf-piece">
          <span>2 ft</span>
          <span class="shelf-sub">Shelf 3</span>
        </div>
        <div class="shelf-piece">
          <span>2 ft</span>
          <span class="shelf-sub">Shelf 4</span>
        </div>
      </div>
    </div>
  </div>

  
  <div class="calc-summary">
    <div class="calc-step highlight" id="calcStep1">
      <span class="calc-badge">Step 1</span>
      <span>9 ½ − 1 ½ = 8 ft</span>
    </div>
    <div class="calc-step" id="calcStep2">
      <span class="calc-badge">Step 2</span>
      <span>8 ÷ 4 = 2 ft</span>
    </div>
  </div>

  <script>
    let currentStep = 0;
    const buttons = document.querySelectorAll('.step-btn');
    const damagedBar = document.getElementById('damagedBar');
    const crossMark = document.getElementById('crossMark');
    const shelvesContainer = document.getElementById('shelvesContainer');
    const calcStep1 = document.getElementById('calcStep1');
    const calcStep2 = document.getElementById('calcStep2');
    const actionLabel = document.getElementById('actionLabel');

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

      if (step === 0) {
        damagedBar.style.opacity = '1';
        crossMark.style.display = 'flex';
        shelvesContainer.style.opacity = '0.35';
        calcStep1.classList.add('highlight');
        calcStep2.classList.remove('highlight');
        actionLabel.textContent = 'Subtract Damaged: 9 ½ − 1 ½ = 8 ft';
      } else {
        damagedBar.style.opacity = '0.4';
        crossMark.style.display = 'flex';
        shelvesContainer.style.opacity = '1';
        calcStep1.classList.remove('highlight');
        calcStep2.classList.add('highlight');
        actionLabel.textContent = '8 ft ÷ 4 = 2 ft per shelf';
      }
    }

    // Initialize with Step 1 highlighted
    setStep(1);
  </script>
</body>
</html>

Solving Multi-Step Distance and Length Problems

<!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, sans-serif;
      background: #ffffff;
      color: #1e2945;
      padding: 16px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      user-select: none;
    }

    .header-tag {
      font-size: 13px;
      font-weight: 700;
      letter-spacing: 0.5px;
      text-transform: uppercase;
      color: #64748b;
      margin-bottom: 4px;
    }

    .main-track-wrap {
      width: 100%;
      max-width: 580px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    /* Overall 10 km dimension line */
    .dimension-bar {
      display: flex;
      align-items: center;
      position: relative;
      height: 24px;
      font-size: 14px;
      font-weight: 700;
      color: #0f172a;
    }
    .dim-line {
      flex: 1;
      height: 2px;
      background: #94a3b8;
      position: relative;
    }
    .dim-line::before, .dim-line::after {
      content: '';
      position: absolute;
      top: -5px;
      width: 2px;
      height: 12px;
      background: #94a3b8;
    }
    .dim-line::before { left: 0; }
    .dim-line::after { right: 0; }
    .dim-label {
      position: absolute;
      left: 50%;
      top: 50%;
      transform: translate(-50%, -50%);
      background: #ffffff;
      padding: 0 8px;
      font-size: 14px;
      font-weight: 800;
      color: #0f172a;
    }

    /* The segmented race bar */
    .track-bar {
      position: relative;
      width: 100%;
      height: 52px;
      background: #f1f5f9;
      border-radius: 10px;
      overflow: hidden;
      display: flex;
      border: 2px solid #cbd5e1;
    }

    .segment {
      height: 100%;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      color: #ffffff;
      font-weight: 700;
      font-size: 13px;
      transition: opacity 0.35s ease, transform 0.35s ease, filter 0.35s ease;
      position: relative;
      overflow: hidden;
      border-right: 1.5px solid rgba(255,255,255,0.4);
    }
    .segment:last-child {
      border-right: none;
    }

    .seg-a {
      width: 24%;
      background: #2563eb;
    }
    .seg-b {
      width: 48%;
      background: #7c3aed;
    }
    .seg-c {
      width: 14%;
      background: #059669;
    }
    .seg-d {
      width: 14%;
      background: #10b981;
    }

    .seg-hidden {
      opacity: 0.18;
      filter: grayscale(80%);
    }

    .seg-name {
      font-size: 11px;
      opacity: 0.95;
      line-height: 1.1;
    }
    .seg-val {
      font-size: 13px;
      font-weight: 800;
      line-height: 1.2;
    }

    /* Sub breakdown cards */
    .calc-row {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 8px;
      width: 100%;
      max-width: 580px;
      margin-top: 4px;
    }

    .calc-card {
      background: #f8fafc;
      border: 1.5px solid #e2e8f0;
      border-radius: 8px;
      padding: 8px 6px;
      text-align: center;
      transition: all 0.3s ease;
    }
    .calc-card.active {
      border-color: #2563eb;
      background: #eff6ff;
      box-shadow: 0 2px 8px rgba(37,99,235,0.12);
    }
    .calc-title {
      font-size: 11px;
      font-weight: 700;
      color: #64748b;
      margin-bottom: 2px;
    }
    .calc-math {
      font-size: 13px;
      font-weight: 800;
      color: #1e2945;
    }
    .calc-card.active .calc-math {
      color: #1d4ed8;
    }

    /* Step explanation badge */
    .step-banner {
      width: 100%;
      max-width: 580px;
      min-height: 38px;
      background: #f1f5f9;
      border-radius: 8px;
      padding: 8px 12px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 14px;
      font-weight: 600;
      color: #334155;
      text-align: center;
    }
    .step-banner strong {
      color: #0f172a;
      margin-right: 4px;
    }

    /* Stepper navigation bar */
    .stepper-nav {
      display: flex;
      align-items: center;
      gap: 8px;
      margin-top: 6px;
    }
    .nav-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 6px 12px;
      font-size: 13px;
      font-weight: 700;
      color: #334155;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 4px;
    }
    .nav-btn:hover {
      background: #e2e8f0;
    }
    .step-btn-group {
      display: flex;
      gap: 4px;
    }
    .step-pill {
      width: 32px;
      height: 32px;
      border-radius: 50%;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      font-size: 13px;
      font-weight: 700;
      color: #64748b;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: all 0.2s ease;
    }
    .step-pill.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
    }

    @media (max-width: 420px) {
      .seg-name { font-size: 10px; }
      .seg-val { font-size: 11px; }
      .calc-math { font-size: 11px; }
      .calc-title { font-size: 10px; }
      .step-banner { font-size: 13px; }
      .step-pill { width: 28px; height: 28px; font-size: 12px; }
    }
  </style>
</head>
<body>

  <div class="header-tag">Total Relay Distance = 10 km</div>

  <div class="main-track-wrap">
    
    <div class="dimension-bar">
      <div class="dim-line"></div>
      <div class="dim-label">10.0 km Total</div>
    </div>

    
    <div class="track-bar">
      <div id="segA" class="segment seg-a">
        <span class="seg-name">Runner A</span>
        <span class="seg-val">2.4 km</span>
      </div>
      <div id="segB" class="segment seg-b">
        <span class="seg-name">Runner B</span>
        <span class="seg-val">4.8 km</span>
      </div>
      <div id="segC" class="segment seg-c">
        <span class="seg-name">C</span>
        <span class="seg-val">1.4 km</span>
      </div>
      <div id="segD" class="segment seg-d">
        <span class="seg-name">D</span>
        <span class="seg-val">1.4 km</span>
      </div>
    </div>
  </div>

  
  <div class="calc-row">
    <div id="card1" class="calc-card">
      <div class="calc-title">Runner B (2 × A)</div>
      <div class="calc-math">2 × 2.4 = 4.8 km</div>
    </div>
    <div id="card2" class="calc-card">
      <div class="calc-title">Remaining</div>
      <div class="calc-math">10 − 7.2 = 2.8 km</div>
    </div>
    <div id="card3" class="calc-card">
      <div class="calc-title">Runners C &amp; D</div>
      <div class="calc-math">2.8 ÷ 2 = 1.4 km</div>
    </div>
  </div>

  
  <div id="stepBanner" class="step-banner">
    Runner A completes 2.4 km
  </div>

  
  <div class="stepper-nav">
    <button id="prevBtn" class="nav-btn" aria-label="Previous step">◀</button>
    <div class="step-btn-group">
      <button class="step-pill active" data-step="0">1</button>
      <button class="step-pill" data-step="1">2</button>
      <button class="step-pill" data-step="2">3</button>
      <button class="step-pill" data-step="3">4</button>
    </div>
    <button id="playBtn" class="nav-btn" aria-label="Auto play">▶</button>
    <button id="nextBtn" class="nav-btn" aria-label="Next step">▶</button>
  </div>

  <script src="{{VENDOR_CDN}}/classace-diagram.js"></script>
  <script>
    const stepsData = [
      {
        text: 'Runner A runs 2.4 km',
        activeSegs: ['segA'],
        activeCard: null
      },
      {
        text: 'Runner B runs 2 × 2.4 = 4.8 km (Total = 7.2 km)',
        activeSegs: ['segA', 'segB'],
        activeCard: 'card1'
      },
      {
        text: 'Remaining track = 10 − 7.2 = 2.8 km',
        activeSegs: ['segA', 'segB'],
        activeCard: 'card2'
      },
      {
        text: 'Runners C & D share equally: 2.8 ÷ 2 = 1.4 km each',
        activeSegs: ['segA', 'segB', 'segC', 'segD'],
        activeCard: 'card3'
      }
    ];

    let currentStep = 0;
    let autoPlayTimer = null;

    const segA = $('#segA');
    const segB = $('#segB');
    const segC = $('#segC');
    const segD = $('#segD');
    const segs = [segA, segB, segC, segD];

    const cards = [$('#card1'), $('#card2'), $('#card3')];
    const pills = $$('.step-pill');
    const banner = $('#stepBanner');
    const playBtn = $('#playBtn');

    function renderStep(idx) {
      currentStep = (idx + stepsData.length) % stepsData.length;
      const data = stepsData[currentStep];

      // Update segment visibility
      segs.forEach(seg => {
        if (data.activeSegs.includes(seg.id)) {
          seg.classList.remove('seg-hidden');
        } else {
          seg.classList.add('seg-hidden');
        }
      });

      // Update cards
      cards.forEach(c => c.classList.remove('active'));
      if (data.activeCard) {
        $(`#${data.activeCard}`).classList.add('active');
      }

      // Update pills
      pills.forEach((p, i) => {
        p.classList.toggle('active', i === currentStep);
      });

      // Update Banner
      banner.textContent = data.text;
    }

    function startAuto() {
      stopAuto();
      playBtn.textContent = '⏸';
      autoPlayTimer = setInterval(() => {
        renderStep(currentStep + 1);
      }, 3500);
    }

    function stopAuto() {
      if (autoPlayTimer) {
        clearInterval(autoPlayTimer);
        autoPlayTimer = null;
      }
      playBtn.textContent = '▶';
    }

    onTap($('#prevBtn'), () => {
      stopAuto();
      renderStep(currentStep - 1);
    });

    onTap($('#nextBtn'), () => {
      stopAuto();
      renderStep(currentStep + 1);
    });

    onTap(playBtn, () => {
      if (autoPlayTimer) {
        stopAuto();
      } else {
        startAuto();
      }
    });

    pills.forEach((pill, i) => {
      onTap(pill, () => {
        stopAuto();
        renderStep(i);
      });
    });

    // Initial render
    renderStep(0);
    startAuto();
  </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;
    }

    body {
      background: #f8f9fa;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      user-select: none;
    }

    .main-layout {
      width: 100%;
      max-width: 380px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    /* Reference Stick */
    .ref-bar {
      background: #fff;
      border: 1.5px dashed #94a3b8;
      border-radius: 8px;
      padding: 6px 12px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-size: 13px;
      font-weight: 600;
      color: #475569;
    }

    .ruler-marks {
      display: flex;
      gap: 3px;
      align-items: flex-end;
      height: 12px;
    }

    .ruler-mark {
      width: 2px;
      background: #cbd5e1;
      height: 6px;
    }

    .ruler-mark.tall {
      height: 12px;
      background: #94a3b8;
    }

    /* Blocks Area */
    .track-container {
      background: #fff;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .track-label {
      font-size: 11px;
      font-weight: 700;
      letter-spacing: 0.5px;
      text-transform: uppercase;
      color: #64748b;
    }

    .blocks-row {
      display: flex;
      align-items: stretch;
      gap: 4px;
      height: 52px;
      width: 100%;
    }

    .block {
      border-radius: 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      font-weight: 700;
      color: #fff;
      text-align: center;
      transition: background-color 0.3s ease, border 0.3s ease;
    }

    .block-blue {
      flex: 4;
      background: #2563eb;
      font-size: 14px;
    }

    .block-orange {
      flex: 1;
      background: #ea580c;
      font-size: 13px;
    }

    .unit-sub {
      font-size: 11px;
      font-weight: 500;
      opacity: 0.9;
    }

    /* Toggle Selector */
    .toggle-row {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 6px;
      background: #e2e8f0;
      padding: 3px;
      border-radius: 8px;
    }

    .toggle-btn {
      border: none;
      background: transparent;
      padding: 7px 4px;
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
      border-radius: 6px;
      cursor: pointer;
      transition: background 0.2s, color 0.2s;
    }

    .toggle-btn.active {
      background: #fff;
      color: #0f172a;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }

    /* Equation Display */
    .equation-card {
      border-radius: 8px;
      padding: 10px 12px;
      display: flex;
      align-items: center;
      gap: 10px;
      font-size: 14px;
      font-weight: 600;
      transition: all 0.3s ease;
    }

    .equation-wrong {
      background: #fef2f2;
      border: 1px solid #fecaca;
      color: #991b1b;
    }

    .equation-correct {
      background: #f0fdf4;
      border: 1px solid #bbf7d0;
      color: #166534;
    }

    .badge {
      font-size: 16px;
      line-height: 1;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .eq-text {
      flex: 1;
      font-variant-numeric: tabular-nums;
    }

    .eq-math {
      font-weight: 700;
    }

    .faded {
      opacity: 0.35;
      filter: grayscale(0.5);
    }
  </style>
</head>
<body>

  <div class="main-layout">
    
    <div class="ref-bar">
      <span>📏 1 m = 100 cm</span>
      <div class="ruler-marks">
        <div class="ruler-mark tall"></div>
        <div class="ruler-mark"></div>
        <div class="ruler-mark"></div>
        <div class="ruler-mark tall"></div>
        <div class="ruler-mark"></div>
        <div class="ruler-mark"></div>
        <div class="ruler-mark tall"></div>
      </div>
    </div>

    
    <div class="track-container">
      <div class="track-label">Combined Length</div>
      <div class="blocks-row">
        <div class="block block-blue" id="blueBlock">
          <span id="blueLabel">200 cm</span>
          <span class="unit-sub" id="blueSub">(2 m)</span>
        </div>
        <div class="block block-orange">
          <span>45 cm</span>
        </div>
      </div>
    </div>

    
    <div class="toggle-row">
      <button class="toggle-btn" id="btnMismatch" onclick="setMode('mismatch')">1. Mixed Units</button>
      <button class="toggle-btn active" id="btnMatch" onclick="setMode('match')">2. Matched Units</button>
    </div>

    
    <div class="equation-card equation-wrong faded" id="cardWrong">
      <span class="badge">❌</span>
      <div class="eq-text">
        <span class="eq-math">2 + 45 = 47</span>
        <span style="font-size: 12px; font-weight: 500; display: block; color: #b91c1c;">Cannot add m + cm</span>
      </div>
    </div>

    <div class="equation-card equation-correct" id="cardCorrect">
      <span class="badge">✅</span>
      <div class="eq-text">
        <span class="eq-math">200 cm + 45 cm = 245 cm</span>
        <span style="font-size: 12px; font-weight: 500; display: block; color: #15803d;">Same unit (or 2.45 m)</span>
      </div>
    </div>
  </div>

  <script>
    function setMode(mode) {
      const btnMismatch = document.getElementById('btnMismatch');
      const btnMatch = document.getElementById('btnMatch');
      const cardWrong = document.getElementById('cardWrong');
      const cardCorrect = document.getElementById('cardCorrect');
      const blueLabel = document.getElementById('blueLabel');
      const blueSub = document.getElementById('blueSub');

      if (mode === 'mismatch') {
        btnMismatch.classList.add('active');
        btnMatch.classList.remove('active');

        cardWrong.classList.remove('faded');
        cardCorrect.classList.add('faded');

        blueLabel.textContent = '2 m';
        blueSub.textContent = '(not converted)';
      } else {
        btnMatch.classList.add('active');
        btnMismatch.classList.remove('active');

        cardCorrect.classList.remove('faded');
        cardWrong.classList.add('faded');

        blueLabel.textContent = '200 cm';
        blueSub.textContent = '(2 m)';
      }
    }
  </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;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      -webkit-tap-highlight-color: transparent;
    }

    :root {
      --blue: #0c4a6e;
      --blue-track: #0284c7;
      --blue-dark: #0369a1;
      --blue-light: #e0f2fe;
      --orange: #9a3412;
      --orange-track: #c2410c;
      --orange-light: #ffedd5;
      --purple: #581c87;
      --purple-light: #f3e8ff;
      --text: #0f172a;
      --muted: #334155;
      --border: #cbd5e1;
    }

    body {
      background: transparent;
      color: var(--text);
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 8px 10px;
      user-select: none;
    }

    .stepper {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      width: 100%;
      max-width: 480px;
    }

    .step-btn {
      flex: 1;
      padding: 7px 4px;
      font-size: clamp(11px, 2.8vw, 13px);
      font-weight: 700;
      border: 1.5px solid #cbd5e1;
      border-radius: 8px;
      background: #f8fafc;
      color: var(--muted);
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 3px;
      transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease;
    }

    .step-btn:hover {
      background: #f1f5f9;
    }

    .step-btn.active {
      border-color: currentColor;
      background: #ffffff;
    }
    .step-btn[data-step="0"].active { color: var(--blue); }
    .step-btn[data-step="1"].active { color: var(--orange); }
    .step-btn[data-step="2"].active { color: var(--purple); }

    .play-btn {
      width: 32px;
      height: 32px;
      border-radius: 8px;
      border: 1.5px solid #cbd5e1;
      background: #f8fafc;
      color: var(--text);
      font-size: 13px;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      flex-shrink: 0;
      transition: background-color 0.2s ease;
    }

    .play-btn:hover {
      background: #f1f5f9;
    }

    .scene-wrap {
      width: 100%;
      max-width: 480px;
      position: relative;
      margin: 2px 0;
    }

    svg {
      width: 100%;
      height: auto;
      display: block;
    }

    .equation-box {
      width: 100%;
      max-width: 480px;
      display: flex;
      flex-direction: column;
      gap: 8px;
      min-height: 72px;
      justify-content: center;
      padding: 2px 0 6px;
    }

    .math-row {
      display: flex;
      align-items: center;
      justify-content: space-between;
      flex-wrap: wrap;
      gap: 4px 8px;
      font-size: clamp(13px, 3.2vw, 15px);
      font-weight: 700;
      color: var(--text);
    }

    .math-pill {
      display: inline-flex;
      align-items: center;
      gap: 4px;
      padding: 3px 8px;
      border-radius: 6px;
      font-size: clamp(12px, 3vw, 14px);
      font-weight: 800;
    }

    .pill-blue { background: var(--blue-light); color: var(--blue); }
    .pill-orange { background: var(--orange-light); color: var(--orange); }
    .pill-purple { background: var(--purple-light); color: var(--purple); }

    .bar-container {
      width: 100%;
      height: 24px;
      background: #e2e8f0;
      border-radius: 6px;
      display: flex;
      overflow: hidden;
    }

    .bar-seg {
      height: 100%;
      transition: opacity 0.3s ease;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: clamp(10px, 2.6vw, 12px);
      font-weight: 800;
      color: #ffffff;
      white-space: nowrap;
      padding: 0 4px;
    }

    .bar-blue { background: var(--blue-dark); width: 80%; }
    .bar-orange { background: var(--orange-track); width: 20%; min-width: 58px; }

    .dimmed {
      opacity: 0.22;
      transition: opacity 0.3s ease;
    }

    .highlighted {
      opacity: 1;
      transition: opacity 0.3s ease;
    }
  </style>
</head>
<body>

  
  <div class="stepper">
    <button class="step-btn active" data-step="0">1 · Track</button>
    <button class="step-btn" data-step="1">2 · Road</button>
    <button class="step-btn" data-step="2">3 · Total</button>
    <button class="play-btn" id="playBtn" title="Auto play">⏸</button>
  </div>

  
  <div class="scene-wrap">
    
    <svg viewBox="-35 0 495 170">
      <defs>
        <marker id="arrow" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1.5 L 8 5 L 0 8.5 z" fill="var(--orange-track)"/>
        </marker>
      </defs>

      
      <g id="trackGroup" class="highlighted">
        
        <rect x="25" y="25" width="170" height="95" rx="47.5" fill="none" stroke="#cbd5e1" stroke-width="14"/>
        <rect id="trackPath" x="25" y="25" width="170" height="95" rx="47.5" fill="none" stroke="var(--blue-track)" stroke-width="14" stroke-linecap="round"/>
        
        
        <circle cx="110" cy="25" r="4" fill="#ffffff" stroke="var(--blue)" stroke-width="2.5"/>
        <text x="110" y="14" font-size="11" font-weight="800" fill="var(--blue)" text-anchor="middle">Lap 1</text>

        <circle cx="195" cy="72.5" r="4" fill="#ffffff" stroke="var(--blue)" stroke-width="2.5"/>
        <text x="178" y="76.5" font-size="11" font-weight="800" fill="var(--blue)" text-anchor="end">Lap 2</text>

        <circle cx="110" cy="120" r="4" fill="#ffffff" stroke="var(--blue)" stroke-width="2.5"/>
        <text x="110" y="138" font-size="11" font-weight="800" fill="var(--blue)" text-anchor="middle">Lap 3</text>

        <circle cx="25" cy="72.5" r="4" fill="#ffffff" stroke="var(--blue)" stroke-width="2.5"/>
        <text x="13" y="76.5" font-size="11" font-weight="800" fill="var(--blue)" text-anchor="end">Lap 4</text>

        
        <text x="110" y="66" font-size="15" font-weight="800" fill="var(--blue)" text-anchor="middle">4 × 1.35 km</text>
        <text x="110" y="85" font-size="13" font-weight="800" fill="var(--text)" text-anchor="middle">= 5.40 km</text>
      </g>

      
      <g id="roadGroup" class="dimmed">
        
        <line x1="205" y1="72.5" x2="385" y2="72.5" stroke="var(--orange-track)" stroke-width="4" stroke-dasharray="7,5" marker-end="url(#arrow)"/>
        
        
        <text x="295" y="55" font-size="13" font-weight="800" fill="var(--orange)" text-anchor="middle">850 m ÷ 1,000</text>
        <text x="295" y="93" font-size="13" font-weight="800" fill="var(--orange)" text-anchor="middle">= 0.85 km</text>

        
        <text x="415" y="78" font-size="30" text-anchor="middle">🏠</text>
        <text x="415" y="100" font-size="11" font-weight="800" fill="var(--text)" text-anchor="middle">Home</text>
      </g>

      
      <text id="runner" x="195" y="75" font-size="20" text-anchor="middle" style="transition: all 0.5s ease;">🏃</text>

      
      <g id="totalSpan" opacity="0" style="transition: opacity 0.3s ease;">
        <path d="M 25 152 L 25 158 L 415 158 L 415 152" fill="none" stroke="var(--purple)" stroke-width="2"/>
        <text x="220" y="150" font-size="13" font-weight="800" fill="var(--purple)" text-anchor="middle">Total Run: 6.25 km</text>
      </g>
    </svg>
  </div>

  
  <div class="equation-box">
    <div id="mathText" class="math-row">
      
    </div>
    
    <div class="bar-container">
      <div id="barBlue" class="bar-seg bar-blue">5.40 km (Track)</div>
      <div id="barOrange" class="bar-seg bar-orange">0.85 km</div>
    </div>
  </div>

  <script>
    const steps = [
      {
        trackDim: false,
        roadDim: true,
        spanVisible: false,
        runnerPos: { x: 195, y: 75 },
        barBlueDim: false,
        barOrangeDim: true,
        mathHtml: `<span>1. Track laps:</span><span class="math-pill pill-blue">4 × 1.35 km = 5.40 km</span>`
      },
      {
        trackDim: true,
        roadDim: false,
        spanVisible: false,
        runnerPos: { x: 300, y: 70 },
        barBlueDim: true,
        barOrangeDim: false,
        mathHtml: `<span>2. Road conversion:</span><span class="math-pill pill-orange">850 m = 0.85 km</span>`
      },
      {
        trackDim: false,
        roadDim: false,
        spanVisible: true,
        runnerPos: { x: 395, y: 75 },
        barBlueDim: false,
        barOrangeDim: false,
        mathHtml: `<span>3. Total distance:</span><span class="math-pill pill-purple">5.40 + 0.85 = 6.25 km</span>`
      }
    ];

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

    const btns = document.querySelectorAll('.step-btn');
    const playBtn = document.getElementById('playBtn');
    const trackGroup = document.getElementById('trackGroup');
    const roadGroup = document.getElementById('roadGroup');
    const totalSpan = document.getElementById('totalSpan');
    const runner = document.getElementById('runner');
    const mathText = document.getElementById('mathText');
    const barBlue = document.getElementById('barBlue');
    const barOrange = document.getElementById('barOrange');

    function renderStep(idx) {
      currentStep = idx;
      const s = steps[idx];

      btns.forEach((b, i) => b.classList.toggle('active', i === idx));

      trackGroup.className.baseVal = s.trackDim ? 'dimmed' : 'highlighted';
      roadGroup.className.baseVal = s.roadDim ? 'dimmed' : 'highlighted';
      totalSpan.style.opacity = s.spanVisible ? '1' : '0';

      runner.setAttribute('x', s.runnerPos.x);
      runner.setAttribute('y', s.runnerPos.y);

      mathText.innerHTML = s.mathHtml;

      barBlue.style.opacity = s.barBlueDim ? '0.22' : '1';
      barOrange.style.opacity = s.barOrangeDim ? '0.22' : '1';
    }

    function nextStep() {
      renderStep((currentStep + 1) % steps.length);
    }

    function startAuto() {
      stopAuto();
      isPlaying = true;
      playBtn.textContent = '⏸';
      timer = setInterval(nextStep, 3500);
    }

    function stopAuto() {
      isPlaying = false;
      playBtn.textContent = '▶';
      if (timer) clearInterval(timer);
    }

    btns.forEach(btn => {
      btn.addEventListener('click', () => {
        stopAuto();
        renderStep(parseInt(btn.dataset.step, 10));
      });
    });

    playBtn.addEventListener('click', () => {
      if (isPlaying) {
        stopAuto();
      } else {
        nextStep();
        startAuto();
      }
    });

    renderStep(0);
    startAuto();
  </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: space-between;
      padding: 12px 16px;
      user-select: none;
    }

    .diagram-area {
      width: 100%;
      max-width: 580px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 8px;
    }

    .svg-container {
      width: 100%;
      aspect-ratio: 600 / 220;
      position: relative;
    }

    svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }

    /* Cards / Display UI */
    .steps-display {
      width: 100%;
      max-width: 580px;
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 8px;
      margin-top: 4px;
    }

    .step-card {
      background: #f8fafc;
      border: 2px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 6px;
      text-align: center;
      cursor: pointer;
      transition: border-color 0.2s, background 0.2s, box-shadow 0.2s;
    }

    .step-card.active {
      background: #eff6ff;
      border-color: #2563eb;
      box-shadow: 0 2px 8px rgba(37, 99, 235, 0.15);
    }

    .step-num {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #64748b;
      margin-bottom: 2px;
    }

    .step-card.active .step-num {
      color: #2563eb;
    }

    .step-val {
      font-size: 14px;
      font-weight: 800;
      color: #1e2945;
      line-height: 1.2;
    }

    .step-card:last-child .step-val {
      color: #059669;
    }

    /* Controls */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 12px;
      margin-top: 8px;
    }

    .btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      color: #1e2945;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 4px;
      transition: background 0.15s;
    }

    .btn:active {
      background: #e2e8f0;
    }

    .btn-play {
      background: #2563eb;
      border-color: #2563eb;
      color: #ffffff;
      min-width: 80px;
      justify-content: center;
    }

    .btn-play:active {
      background: #1d4ed8;
    }

    .dots {
      display: flex;
      gap: 6px;
    }

    .dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: #cbd5e1;
      cursor: pointer;
      transition: background 0.2s, transform 0.2s;
    }

    .dot.active {
      background: #2563eb;
      transform: scale(1.25);
    }

    /* Tick Highlights */
    .highlight-band {
      transition: opacity 0.3s ease;
      opacity: 0;
    }
    .highlight-band.visible {
      opacity: 1;
    }

    @media (max-width: 440px) {
      .step-val { font-size: 12px; }
      .step-num { font-size: 9px; }
      body { padding: 8px; }
    }
  </style>
</head>
<body>

  <div class="diagram-area">
    <div class="svg-container">
      <svg viewBox="0 0 600 220">
        <defs>
          
          <linearGradient id="screwBody" x1="0" y1="0" x2="0" y2="1">
            <stop offset="0%" stop-color="#94a3b8"/>
            <stop offset="30%" stop-color="#f1f5f9"/>
            <stop offset="70%" stop-color="#cbd5e1"/>
            <stop offset="100%" stop-color="#64748b"/>
          </linearGradient>
          <linearGradient id="screwHead" x1="0" y1="0" x2="0" y2="1">
            <stop offset="0%" stop-color="#cbd5e1"/>
            <stop offset="50%" stop-color="#f8fafc"/>
            <stop offset="100%" stop-color="#475569"/>
          </linearGradient>
          <linearGradient id="rulerWood" x1="0" y1="0" x2="0" y2="1">
            <stop offset="0%" stop-color="#fffbeb"/>
            <stop offset="100%" stop-color="#fef3c7"/>
          </linearGradient>
        </defs>

        
        <rect x="30" y="80" width="540" height="80" rx="4" fill="url(#rulerWood)" stroke="#d97706" stroke-width="1.5"/>

        
        
        <rect id="bandWhole" class="highlight-band" x="50" y="80" width="333.33" height="80" fill="#3b82f6" fill-opacity="0.12"/>
        
        <rect id="bandFraction" class="highlight-band" x="383.33" y="80" width="62.5" height="80" fill="#f59e0b" fill-opacity="0.25"/>

        
        
        <g stroke="#1e2945" stroke-linecap="round">
          
          <g id="ticksGroup"></g>
        </g>

        
        <text x="50" y="142" font-size="16" font-weight="bold" fill="#1e2945" text-anchor="middle">0</text>
        <text x="216.66" y="142" font-size="16" font-weight="bold" fill="#1e2945" text-anchor="middle">1</text>
        <text x="383.33" y="142" font-size="16" font-weight="bold" fill="#1e2945" text-anchor="middle">2</text>
        <text x="550" y="142" font-size="16" font-weight="bold" fill="#1e2945" text-anchor="middle">3</text>
        <text x="540" y="102" font-size="10" font-weight="bold" fill="#92400e" text-anchor="end">INCH (1/16)</text>

        
        <line x1="50" y1="20" x2="50" y2="80" stroke="#64748b" stroke-width="1.5" stroke-dasharray="3,3"/>
        <line id="guideWhole" class="highlight-band" x1="383.33" y1="42" x2="383.33" y2="80" stroke="#2563eb" stroke-width="1.5" stroke-dasharray="3,3"/>
        <line id="guideTip" x1="445.83" y1="20" x2="445.83" y2="80" stroke="#dc2626" stroke-width="1.5" stroke-dasharray="3,3"/>

        
        
        <g id="screw" transform="translate(0, 42)">
          
          <path d="M 50 3 L 56 10 L 56 30 L 50 37 Z" fill="url(#screwHead)" stroke="#475569" stroke-width="1"/>
          
          <rect x="56" y="14" width="355" height="12" fill="url(#screwBody)"/>
          
          <path d="
            M 90 13 L 95 27 M 115 13 L 120 27 M 140 13 L 145 27 M 165 13 L 170 27
            M 190 13 L 195 27 M 215 13 L 220 27 M 240 13 L 245 27 M 265 13 L 270 27
            M 290 13 L 295 27 M 315 13 L 320 27 M 340 13 L 345 27 M 365 13 L 370 27
            M 390 13 L 395 27 M 410 14 L 414 26
          " stroke="#64748b" stroke-width="3" stroke-linecap="round"/>
          
          <polygon points="411,14 445.83,20 411,26" fill="url(#screwBody)" stroke="#64748b" stroke-width="0.5"/>
          
          <path d="M 425 16 L 428 24" stroke="#64748b" stroke-width="2.5" stroke-linecap="round"/>
        </g>

        
        
        <g id="annotStep1" class="highlight-band">
          <path d="M 50 25 L 50 18 L 216.66 18 L 383.33 18 L 383.33 25" fill="none" stroke="#2563eb" stroke-width="2"/>
          <rect x="180" y="6" width="74" height="22" rx="4" fill="#2563eb"/>
          <text x="217" y="21" font-size="12" font-weight="bold" fill="#ffffff" text-anchor="middle">2 INCHES</text>
        </g>

        
        <g id="annotStep2" class="highlight-band">
          <path d="M 383.33 72 Q 414.58 60 445.83 72" fill="none" stroke="#d97706" stroke-width="2"/>
          <rect x="390" y="20" width="50" height="20" rx="4" fill="#d97706"/>
          <text x="415" y="34" font-size="11" font-weight="bold" fill="#ffffff" text-anchor="middle">+6/16</text>
          
          <circle cx="393.75" cy="77" r="2.5" fill="#d97706"/>
          <circle cx="404.16" cy="77" r="2.5" fill="#d97706"/>
          <circle cx="414.58" cy="77" r="2.5" fill="#d97706"/>
          <circle cx="425.00" cy="77" r="2.5" fill="#d97706"/>
          <circle cx="435.41" cy="77" r="2.5" fill="#d97706"/>
          <circle cx="445.83" cy="77" r="2.5" fill="#d97706"/>
        </g>

        
        <g id="annotFinal" class="highlight-band">
          <polygon points="445.83,32 440,24 451.66,24" fill="#059669"/>
          <rect x="385" y="0" width="122" height="24" rx="4" fill="#059669"/>
          <text x="446" y="16" font-size="12" font-weight="bold" fill="#ffffff" text-anchor="middle">2 ⅜ in  (6.03 cm)</text>
        </g>
      </svg>
    </div>

    
    <div class="steps-display">
      <div class="step-card active" onclick="setStep(0)">
        <div class="step-num">Step 1</div>
        <div class="step-val">Whole = 2</div>
      </div>
      <div class="step-card" onclick="setStep(1)">
        <div class="step-num">Step 2</div>
        <div class="step-val">Ticks = ⁶⁄₁₆</div>
      </div>
      <div class="step-card" onclick="setStep(2)">
        <div class="step-num">Step 3</div>
        <div class="step-val">Reduce = ⅜</div>
      </div>
      <div class="step-card" onclick="setStep(3)">
        <div class="step-num">Result</div>
        <div class="step-val">2 ⅜ in</div>
      </div>
    </div>

    
    <div class="controls">
      <button class="btn" onclick="prevStep()">◀</button>
      <button id="playBtn" class="btn btn-play" onclick="togglePlay()">⏸ Pause</button>
      <button class="btn" onclick="nextStep()">▶</button>
      <div class="dots">
        <span class="dot active" onclick="setStep(0)"></span>
        <span class="dot" onclick="setStep(1)"></span>
        <span class="dot" onclick="setStep(2)"></span>
        <span class="dot" onclick="setStep(3)"></span>
      </div>
    </div>
  </div>

  <script>
    // Generate ruler ticks mathematically
    const ticksGroup = document.getElementById('ticksGroup');
    const startX = 50;
    const inchWidth = 166.666;
    const sixteenth = inchWidth / 16;

    for (let i = 0; i <= 48; i++) {
      const x = startX + i * sixteenth;
      let h = 8;
      let strokeWidth = 1;

      if (i % 16 === 0) {
        h = 32;
        strokeWidth = 2;
      } else if (i % 8 === 0) {
        h = 24;
        strokeWidth = 1.5;
      } else if (i % 4 === 0) {
        h = 18;
        strokeWidth = 1.2;
      } else if (i % 2 === 0) {
        h = 13;
        strokeWidth = 1;
      }

      const line = document.createElementNS('http://www.w3.org/2000/svg', 'line');
      line.setAttribute('x1', x);
      line.setAttribute('y1', 80);
      line.setAttribute('x2', x);
      line.setAttribute('y2', 80 + h);
      line.setAttribute('stroke-width', strokeWidth);
      ticksGroup.appendChild(line);
    }

    // Step animation state
    let currentStep = 0;
    let isPlaying = true;
    let timer = null;

    const cards = document.querySelectorAll('.step-card');
    const dots = document.querySelectorAll('.dot');
    const playBtn = document.getElementById('playBtn');

    // Visual Elements
    const bandWhole = document.getElementById('bandWhole');
    const bandFraction = document.getElementById('bandFraction');
    const guideWhole = document.getElementById('guideWhole');
    const annotStep1 = document.getElementById('annotStep1');
    const annotStep2 = document.getElementById('annotStep2');
    const annotFinal = document.getElementById('annotFinal');

    function updateVisuals() {
      // Clear cards & dots
      cards.forEach((c, idx) => c.classList.toggle('active', idx === currentStep));
      dots.forEach((d, idx) => d.classList.toggle('active', idx === currentStep));

      // Reset all highlights
      bandWhole.classList.remove('visible');
      bandFraction.classList.remove('visible');
      guideWhole.classList.remove('visible');
      annotStep1.classList.remove('visible');
      annotStep2.classList.remove('visible');
      annotFinal.classList.remove('visible');

      if (currentStep === 0) {
        bandWhole.classList.add('visible');
        annotStep1.classList.add('visible');
      } else if (currentStep === 1) {
        bandWhole.classList.add('visible');
        bandFraction.classList.add('visible');
        guideWhole.classList.add('visible');
        annotStep2.classList.add('visible');
      } else if (currentStep === 2) {
        bandWhole.classList.add('visible');
        bandFraction.classList.add('visible');
        guideWhole.classList.add('visible');
        annotStep2.classList.add('visible');
      } else if (currentStep === 3) {
        bandWhole.classList.add('visible');
        bandFraction.classList.add('visible');
        guideWhole.classList.add('visible');
        annotFinal.classList.add('visible');
      }
    }

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

    function nextStep() {
      currentStep = (currentStep + 1) % 4;
      updateVisuals();
    }

    function prevStep() {
      currentStep = (currentStep - 1 + 4) % 4;
      updateVisuals();
    }

    function togglePlay() {
      isPlaying = !isPlaying;
      playBtn.textContent = isPlaying ? '⏸ Pause' : '▶ Play';
      if (isPlaying) startAutoPlay();
      else clearInterval(timer);
    }

    function startAutoPlay() {
      clearInterval(timer);
      timer = setInterval(() => {
        nextStep();
      }, 3500);
    }

    // Initialize
    updateVisuals();
    startAutoPlay();
  </script>
</body>
</html>

Reading Rulers with Fractional and Millimeter Increments

<!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>Reading Millimeters on a Ruler</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 16px 12px;
      user-select: none;
      width: 100%;
    }

    .header-badges {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 12px;
      margin-bottom: 12px;
      flex-wrap: wrap;
    }

    .badge {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      padding: 6px 14px;
      border-radius: 8px;
      font-weight: 700;
      font-size: 16px;
    }

    .badge-cm {
      background: #eff6ff;
      color: #1d4ed8;
      border: 1px solid #bfdbfe;
    }

    .badge-mm {
      background: #f0fdf4;
      color: #15803d;
      border: 1px solid #bbf7d0;
    }

    .badge-eq {
      font-size: 18px;
      font-weight: 800;
      color: #64748b;
    }

    .ruler-svg-container {
      width: 100%;
      max-width: 600px;
      aspect-ratio: 600 / 300;
      position: relative;
    }

    svg {
      width: 100%;
      height: 100%;
      display: block;
    }

    .toggle-row {
      display: flex;
      gap: 8px;
      margin-top: 14px;
      justify-content: center;
      flex-wrap: wrap;
    }

    .toggle-btn {
      padding: 8px 16px;
      border-radius: 20px;
      border: 1px solid #cbd5e1;
      background: #f8fafc;
      color: #475569;
      font-size: 14px;
      font-weight: 600;
      cursor: pointer;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
    }

    .toggle-btn.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
    }

    /* Interactive state visibility */
    .step-fade {
      transition: opacity 0.3s ease;
    }
  </style>
</head>
<body>

  
  <div class="header-badges">
    <div class="badge badge-cm">4.7 cm</div>
    <span class="badge-eq">=</span>
    <div class="badge badge-mm">47 mm</div>
  </div>

  
  <div class="ruler-svg-container">
    <svg viewBox="0 0 600 300" fill="none" xmlns="http://www.w3.org/2000/svg">
      <defs>
        
        <linearGradient id="clipGrad" x1="0%" y1="0%" x2="0%" y2="100%">
          <stop offset="0%" stop-color="#22c55e" />
          <stop offset="50%" stop-color="#16a34a" />
          <stop offset="100%" stop-color="#15803d" />
        </linearGradient>
        
        <linearGradient id="rulerGrad" x1="0%" y1="0%" x2="0%" y2="100%">
          <stop offset="0%" stop-color="#fef3c7" />
          <stop offset="100%" stop-color="#fde68a" />
        </linearGradient>
        
        <marker id="arrow" viewBox="0 0 6 6" refX="5" refY="3" markerWidth="6" markerHeight="6" orient="auto">
          <path d="M0,1 L5,3 L0,5 Z" fill="#2563eb"/>
        </marker>
      </defs>

      
      
      <g id="paperclipGroup">
        
        <path d="M 10,48 L 22,40 L 16,56 L 28,48" stroke="#94a3b8" stroke-width="2" fill="none" stroke-linecap="round" />
        <text x="24" y="28" font-size="12" fill="#64748b" font-weight="600">starts at 0 cm</text>
        
        
        
        <path d="M 28,48 L 325,48 A 16,16 0 0,1 345,64 A 16,16 0 0,1 325,80 L 70,80 A 12,12 0 0,1 58,68 A 12,12 0 0,1 70,56 L 295,56 A 8,8 0 0,1 303,64 A 8,8 0 0,1 295,72 L 100,72"
              stroke="url(#clipGrad)" stroke-width="5" stroke-linecap="round" stroke-linejoin="round" fill="none" />
      </g>

      
      <line x1="345" y1="64" x2="345" y2="180" stroke="#16a34a" stroke-width="2.5" stroke-dasharray="4 3" />
      
      
      <circle cx="345" cy="64" r="4.5" fill="#15803d" />

      
      
      
      
      <g id="ruler">
        <rect x="20" y="180" width="560" height="95" rx="6" fill="url(#rulerGrad)" stroke="#d97706" stroke-width="1.5" />

        
        <line x1="20" y1="180" x2="580" y2="180" stroke="#92400e" stroke-width="2" />

        
        
        
        
        
        <line x1="30" y1="180" x2="30" y2="194" stroke="#78350f" stroke-width="1.5" />
        
        <line x1="65" y1="180" x2="65" y2="194" stroke="#78350f" stroke-width="1.5" />

        
        <line x1="100" y1="180" x2="100" y2="225" stroke="#78350f" stroke-width="3" />
        <text x="100" y="254" font-size="22" font-weight="800" fill="#78350f" text-anchor="middle">4</text>

        
        <line x1="135" y1="180" x2="135" y2="196" stroke="#78350f" stroke-width="1.5" />
        
        <line x1="170" y1="180" x2="170" y2="196" stroke="#78350f" stroke-width="1.5" />
        
        <line x1="205" y1="180" x2="205" y2="196" stroke="#78350f" stroke-width="1.5" />
        
        <line x1="240" y1="180" x2="240" y2="196" stroke="#78350f" stroke-width="1.5" />

        
        <line x1="275" y1="180" x2="275" y2="212" stroke="#d97706" stroke-width="3" />

        
        <line x1="310" y1="180" x2="310" y2="196" stroke="#78350f" stroke-width="1.5" />
        
        <line x1="345" y1="180" x2="345" y2="202" stroke="#16a34a" stroke-width="3" />
        
        <line x1="380" y1="180" x2="380" y2="196" stroke="#78350f" stroke-width="1.5" />
        
        <line x1="415" y1="180" x2="415" y2="196" stroke="#78350f" stroke-width="1.5" />

        
        <line x1="450" y1="180" x2="450" y2="225" stroke="#78350f" stroke-width="3" />
        <text x="450" y="254" font-size="22" font-weight="800" fill="#78350f" text-anchor="middle">5</text>

        
        <line x1="485" y1="180" x2="485" y2="196" stroke="#78350f" stroke-width="1.5" />
        <line x1="520" y1="180" x2="520" y2="196" stroke="#78350f" stroke-width="1.5" />
        <line x1="555" y1="180" x2="555" y2="196" stroke="#78350f" stroke-width="1.5" />

        
        <text x="560" y="250" font-size="14" font-weight="700" fill="#92400e" text-anchor="end">cm</text>
      </g>

      
      <g id="halfCmHighlight">
        <rect x="245" y="222" width="60" height="20" rx="4" fill="#fef3c7" stroke="#d97706" stroke-width="1" />
        <text x="275" y="236" font-size="11" font-weight="700" fill="#b45309" text-anchor="middle">5 mm</text>
      </g>

      
      <g id="countingLayer" class="step-fade">
        
        <path d="M 100,175 Q 117.5,152 135,175" stroke="#2563eb" stroke-width="2" fill="none" />
        
        <path d="M 135,175 Q 152.5,152 170,175" stroke="#2563eb" stroke-width="2" fill="none" />
        
        <path d="M 170,175 Q 187.5,152 205,175" stroke="#2563eb" stroke-width="2" fill="none" />
        
        <path d="M 205,175 Q 222.5,152 240,175" stroke="#2563eb" stroke-width="2" fill="none" />
        
        <path d="M 240,175 Q 257.5,152 275,175" stroke="#2563eb" stroke-width="2" fill="none" />
        
        <path d="M 275,175 Q 292.5,152 310,175" stroke="#2563eb" stroke-width="2" fill="none" />
        
        <path d="M 310,175 Q 327.5,152 345,175" stroke="#2563eb" stroke-width="2" fill="none" />

        
        <g transform="translate(117.5, 150)">
          <circle cx="0" cy="0" r="9" fill="#2563eb" />
          <text x="0" y="3.5" font-size="11" font-weight="700" fill="#ffffff" text-anchor="middle">1</text>
        </g>
        <g transform="translate(152.5, 150)">
          <circle cx="0" cy="0" r="9" fill="#2563eb" />
          <text x="0" y="3.5" font-size="11" font-weight="700" fill="#ffffff" text-anchor="middle">2</text>
        </g>
        <g transform="translate(187.5, 150)">
          <circle cx="0" cy="0" r="9" fill="#2563eb" />
          <text x="0" y="3.5" font-size="11" font-weight="700" fill="#ffffff" text-anchor="middle">3</text>
        </g>
        <g transform="translate(222.5, 150)">
          <circle cx="0" cy="0" r="9" fill="#2563eb" />
          <text x="0" y="3.5" font-size="11" font-weight="700" fill="#ffffff" text-anchor="middle">4</text>
        </g>
        <g transform="translate(257.5, 150)">
          <circle cx="0" cy="0" r="9" fill="#2563eb" />
          <text x="0" y="3.5" font-size="11" font-weight="700" fill="#ffffff" text-anchor="middle">5</text>
        </g>
        <g transform="translate(292.5, 150)">
          <circle cx="0" cy="0" r="9" fill="#2563eb" />
          <text x="0" y="3.5" font-size="11" font-weight="700" fill="#ffffff" text-anchor="middle">6</text>
        </g>
        <g transform="translate(327.5, 150)">
          <circle cx="0" cy="0" r="9" fill="#2563eb" />
          <text x="0" y="3.5" font-size="11" font-weight="700" fill="#ffffff" text-anchor="middle">7</text>
        </g>
      </g>

      
      <g id="endLabel">
        
        <rect x="317" y="98" width="56" height="24" rx="6" fill="#15803d" />
        <text x="345" y="115" font-size="13" font-weight="800" fill="#ffffff" text-anchor="middle">+7 mm</text>
        
        <polygon points="341,122 349,122 345,127" fill="#15803d" />
      </g>
    </svg>
  </div>

  
  <div class="toggle-row">
    <button class="toggle-btn active" id="btnAll" onclick="setMode('all')">Show All</button>
    <button class="toggle-btn" id="btnCount" onclick="setMode('count')">Count +7 mm</button>
    <button class="toggle-btn" id="btnFinal" onclick="setMode('final')">Measurement</button>
  </div>

  <script>
    function setMode(mode) {
      const countLayer = document.getElementById('countingLayer');
      const endLabel = document.getElementById('endLabel');
      const btnAll = document.getElementById('btnAll');
      const btnCount = document.getElementById('btnCount');
      const btnFinal = document.getElementById('btnFinal');

      btnAll.classList.remove('active');
      btnCount.classList.remove('active');
      btnFinal.classList.remove('active');

      if (mode === 'all') {
        btnAll.classList.add('active');
        countLayer.style.opacity = '1';
        endLabel.style.opacity = '1';
      } else if (mode === 'count') {
        btnCount.classList.add('active');
        countLayer.style.opacity = '1';
        endLabel.style.opacity = '0';
      } else if (mode === 'final') {
        btnFinal.classList.add('active');
        countLayer.style.opacity = '0';
        endLabel.style.opacity = '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">
  <title>Fractional Ruler Increments</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      -webkit-tap-highlight-color: transparent;
    }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background-color: #f8f9fa;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100vh;
      user-select: none;
    }

    /* Top Filters */
    .filter-bar {
      display: flex;
      flex-wrap: wrap;
      gap: 6px;
      justify-content: center;
      width: 100%;
      max-width: 580px;
    }
    .filter-btn {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 9999px;
      padding: 5px 10px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      transition: all 0.2s ease;
      color: #64748b;
    }
    .filter-btn[data-tier="all"].active {
      background: #0f172a;
      border-color: #0f172a;
      color: #ffffff;
    }
    .filter-btn[data-tier="2"] { color: #0284c7; }
    .filter-btn[data-tier="2"].active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
    }
    .filter-btn[data-tier="4"] { color: #4f46e5; }
    .filter-btn[data-tier="4"].active {
      background: #4f46e5;
      border-color: #4f46e5;
      color: #ffffff;
    }
    .filter-btn[data-tier="8"] { color: #059669; }
    .filter-btn[data-tier="8"].active {
      background: #059669;
      border-color: #059669;
      color: #ffffff;
    }
    .filter-btn[data-tier="16"] { color: #64748b; }
    .filter-btn[data-tier="16"].active {
      background: #64748b;
      border-color: #64748b;
      color: #ffffff;
    }

    /* Ruler Container */
    .ruler-container {
      width: 100%;
      max-width: 560px;
      margin: 8px 0;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }

    .tick-line {
      transition: opacity 0.25s ease, stroke-width 0.2s ease;
      stroke-linecap: round;
    }
    .hit-rect {
      cursor: pointer;
      fill: transparent;
    }

    /* Dynamic Readout */
    .readout-card {
      width: 100%;
      max-width: 560px;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 14px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.05);
      min-height: 52px;
    }
    .readout-left {
      display: flex;
      align-items: baseline;
      gap: 8px;
    }
    .main-fraction {
      font-size: 24px;
      font-weight: 800;
      line-height: 1;
      font-variant-numeric: tabular-nums;
    }
    .sub-fraction {
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
    }
    .tier-desc {
      font-size: 12px;
      font-weight: 600;
      text-align: right;
      color: #475569;
    }

    /* Grid Badges */
    .badge-grid {
      display: grid;
      grid-template-columns: repeat(8, 1fr);
      gap: 5px;
      width: 100%;
      max-width: 560px;
    }
    .badge-btn {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 6px;
      padding: 6px 2px;
      font-size: 12px;
      font-weight: 700;
      color: #64748b;
      cursor: pointer;
      transition: all 0.15s ease;
      text-align: center;
    }
    .badge-btn.dimmed {
      opacity: 0.25;
    }
    .badge-btn.active {
      color: #ffffff !important;
    }

    /* Color Classes */
    .c-slate { color: #64748b; }
    .c-emerald { color: #059669; }
    .c-indigo { color: #4f46e5; }
    .c-blue { color: #0284c7; }
    .c-dark { color: #0f172a; }
  </style>
</head>
<body>

  
  <div class="filter-bar">
    <button class="filter-btn active" data-tier="all" onclick="setFilter('all')">All Marks</button>
    <button class="filter-btn" data-tier="2" onclick="setFilter('2')">Halves (½)</button>
    <button class="filter-btn" data-tier="4" onclick="setFilter('4')">Fourths (¼)</button>
    <button class="filter-btn" data-tier="8" onclick="setFilter('8')">Eighths (⅛)</button>
    <button class="filter-btn" data-tier="16" onclick="setFilter('16')">Sixteenths (¹⁄₁₆)</button>
  </div>

  
  <div class="ruler-container">
    <svg viewBox="0 0 540 120" id="rulerSvg">
      
      <rect x="10" y="8" width="520" height="96" rx="8" fill="#ffffff" stroke="#cbd5e1" stroke-width="2"/>
      
      
      <line x1="20" y1="90" x2="520" y2="90" stroke="#0f172a" stroke-width="2.5"/>

      
      <g id="indicator" transform="translate(270, 0)" style="transition: transform 0.2s ease;">
        <line y1="16" y2="90" stroke="#0284c7" stroke-width="1.5" stroke-dasharray="2 2" opacity="0.7"/>
        <circle cy="16" r="4.5" fill="#0284c7"/>
      </g>

      
      <g id="ticksGroup"></g>

      
      <text x="20" y="105" font-size="13" font-weight="700" fill="#0f172a" text-anchor="middle">0</text>
      <text x="520" y="105" font-size="13" font-weight="700" fill="#0f172a" text-anchor="middle">1 in</text>

      
      <g id="hitTargetsGroup"></g>
    </svg>
  </div>

  
  <div class="readout-card">
    <div class="readout-left">
      <span class="main-fraction" id="readoutMain">1/2 in</span>
      <span class="sub-fraction" id="readoutSub">8/16 in</span>
    </div>
    <div class="tier-desc" id="readoutDesc">Half mark • Splits inch in 2</div>
  </div>

  
  <div class="badge-grid" id="badgeGrid"></div>

  <script>
    // Fraction Metadata
    const data = [
      { i: 0, num: 0, den: 1, label: "0 in", sub: "0/16 in", tier: 1, h: 68, w: 3.5, col: "#0f172a", desc: "Start point (0 in)" },
      { i: 1, num: 1, den: 16, label: "1/16 in", sub: "Smallest tick", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 1 of 16 parts" },
      { i: 2, num: 1, den: 8, label: "1/8 in", sub: "2/16 in", tier: 8, h: 30, w: 2.0, col: "#059669", desc: "Medium-short • 1 of 8 parts" },
      { i: 3, num: 3, den: 16, label: "3/16 in", sub: "3/16 in", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 3 of 16 parts" },
      { i: 4, num: 1, den: 4, label: "1/4 in", sub: "4/16 in", tier: 4, h: 42, w: 2.5, col: "#4f46e5", desc: "Medium-tall • 1 of 4 parts" },
      { i: 5, num: 5, den: 16, label: "5/16 in", sub: "5/16 in", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 5 of 16 parts" },
      { i: 6, num: 3, den: 8, label: "3/8 in", sub: "6/16 in", tier: 8, h: 30, w: 2.0, col: "#059669", desc: "Medium-short • 3 of 8 parts" },
      { i: 7, num: 7, den: 16, label: "7/16 in", sub: "7/16 in", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 7 of 16 parts" },
      { i: 8, num: 1, den: 2, label: "1/2 in", sub: "8/16 in", tier: 2, h: 54, w: 3.0, col: "#0284c7", desc: "Tall mark • Center half" },
      { i: 9, num: 9, den: 16, label: "9/16 in", sub: "9/16 in", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 9 of 16 parts" },
      { i: 10, num: 5, den: 8, label: "5/8 in", sub: "10/16 in", tier: 8, h: 30, w: 2.0, col: "#059669", desc: "Medium-short • 5 of 8 parts" },
      { i: 11, num: 11, den: 16, label: "11/16 in", sub: "11/16 in", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 11 of 16 parts" },
      { i: 12, num: 3, den: 4, label: "3/4 in", sub: "12/16 in", tier: 4, h: 42, w: 2.5, col: "#4f46e5", desc: "Medium-tall • 3 of 4 parts" },
      { i: 13, num: 13, den: 16, label: "13/16 in", sub: "13/16 in", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 13 of 16 parts" },
      { i: 14, num: 7, den: 8, label: "7/8 in", sub: "14/16 in", tier: 8, h: 30, w: 2.0, col: "#059669", desc: "Medium-short • 7 of 8 parts" },
      { i: 15, num: 15, den: 16, label: "15/16 in", sub: "15/16 in", tier: 16, h: 18, w: 1.5, col: "#64748b", desc: "Short mark • 15 of 16 parts" },
      { i: 16, num: 1, den: 1, label: "1 in", sub: "16/16 in", tier: 1, h: 68, w: 3.5, col: "#0f172a", desc: "Full inch (16/16)" }
    ];

    let selectedIdx = 8;
    let activeFilter = 'all';

    const startX = 20;
    const totalW = 500;
    const stepX = totalW / 16;
    const baseY = 90;

    const ticksGroup = document.getElementById('ticksGroup');
    const hitTargetsGroup = document.getElementById('hitTargetsGroup');
    const badgeGrid = document.getElementById('badgeGrid');

    // Build SVG ticks & targets
    data.forEach((d) => {
      const x = startX + d.i * stepX;
      const y1 = baseY;
      const y2 = baseY - d.h;

      // Tick line
      const line = document.createElementNS("http://www.w3.org/2000/svg", "line");
      line.setAttribute("x1", x);
      line.setAttribute("y1", y1);
      line.setAttribute("x2", x);
      line.setAttribute("y2", y2);
      line.setAttribute("stroke", d.col);
      line.setAttribute("stroke-width", d.w);
      line.setAttribute("class", "tick-line");
      line.setAttribute("id", `tick-${d.i}`);
      ticksGroup.appendChild(line);

      // Hit area
      const rect = document.createElementNS("http://www.w3.org/2000/svg", "rect");
      rect.setAttribute("x", x - 12);
      rect.setAttribute("y", 12);
      rect.setAttribute("width", 24);
      rect.setAttribute("height", 84);
      rect.setAttribute("class", "hit-rect");
      rect.onmouseenter = () => selectIncrement(d.i);
      rect.onclick = () => selectIncrement(d.i);
      hitTargetsGroup.appendChild(rect);
    });

    // Build bottom grid badges (1 to 16)
    for (let i = 1; i <= 16; i++) {
      const d = data[i];
      const btn = document.createElement('button');
      btn.className = 'badge-btn';
      btn.id = `badge-${i}`;
      btn.textContent = d.den === 1 ? '1"' : `${d.num}/${d.den}`;
      btn.style.color = d.col;
      btn.onclick = () => selectIncrement(i);
      btn.onmouseenter = () => selectIncrement(i);
      badgeGrid.appendChild(btn);
    }

    function isTierVisible(itemTier, filter) {
      if (filter === 'all') return true;
      const fNum = parseInt(filter);
      return itemTier <= fNum;
    }

    function setFilter(tier) {
      activeFilter = tier;
      document.querySelectorAll('.filter-btn').forEach(btn => {
        btn.classList.toggle('active', btn.dataset.tier === tier);
      });
      updateVisuals();
    }

    function selectIncrement(idx) {
      selectedIdx = idx;
      updateVisuals();
    }

    function updateVisuals() {
      const sel = data[selectedIdx];
      const x = startX + sel.i * stepX;

      // Update indicator
      const ind = document.getElementById('indicator');
      ind.setAttribute('transform', `translate(${x}, 0)`);
      const bead = ind.querySelector('circle');
      const line = ind.querySelector('line');
      bead.setAttribute('fill', sel.col);
      line.setAttribute('stroke', sel.col);

      // Update ticks opacity and width
      data.forEach(d => {
        const tick = document.getElementById(`tick-${d.i}`);
        const visibleByFilter = isTierVisible(d.tier, activeFilter);
        const isCurrent = d.i === selectedIdx;

        if (!visibleByFilter) {
          tick.style.opacity = '0.12';
          tick.setAttribute('stroke-width', d.w);
        } else {
          tick.style.opacity = (isCurrent || activeFilter !== 'all') ? '1' : '0.85';
          tick.setAttribute('stroke-width', isCurrent ? d.w + 1.5 : d.w);
        }
      });

      // Update badges
      for (let i = 1; i <= 16; i++) {
        const d = data[i];
        const badge = document.getElementById(`badge-${i}`);
        const visibleByFilter = isTierVisible(d.tier, activeFilter);
        const isCurrent = (i === selectedIdx);

        badge.classList.toggle('dimmed', !visibleByFilter);

        if (isCurrent) {
          badge.classList.add('active');
          badge.style.backgroundColor = d.col;
          badge.style.borderColor = d.col;
        } else {
          badge.classList.remove('active');
          badge.style.backgroundColor = '#ffffff';
          badge.style.borderColor = '#e2e8f0';
        }
      }

      // Update Readout Card
      const readoutMain = document.getElementById('readoutMain');
      const readoutSub = document.getElementById('readoutSub');
      const readoutDesc = document.getElementById('readoutDesc');

      readoutMain.textContent = sel.label;
      readoutMain.style.color = sel.col;
      readoutSub.textContent = (sel.sub === sel.label || sel.den === 16) ? '' : `(${sel.sub})`;
      readoutDesc.textContent = sel.desc;
    }

    // Initial render
    updateVisuals();
  </script>
</body>
</html>

OGM.5.MD.2

Aligned learning resources

Related diagrams