<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Combustion of Hydrogen: Molecular Reaction & Shockwave</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
      padding: 12px;
      user-select: none;
    }
    .diagram-wrap {
      width: 100%;
      max-width: 600px;
      margin: 0 auto;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }

    /* Section transitions */
    #group-reactants,
    #group-products,
    #center-reaction,
    #shockwave-section {
      transition: opacity 0.35s ease;
    }

    /* Controls */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      margin-top: 14px;
      flex-wrap: wrap;
      width: 100%;
      max-width: 600px;
    }
    .step-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 7px 14px;
      border-radius: 20px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      transition: background 0.2s ease, border-color 0.2s ease, color 0.2s ease;
    }
    .step-btn:hover {
      background: #e2e8f0;
    }
    .step-btn.active {
      background: #0284c7;
      border-color: #0369a1;
      color: #ffffff;
    }
    .sound-btn {
      background: #f8fafc;
      border: 1px solid #94a3b8;
      color: #1e2945;
      padding: 7px 14px;
      border-radius: 20px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 5px;
      transition: background 0.2s ease, border-color 0.2s ease;
    }
    .sound-btn:hover {
      background: #f1f5f9;
      border-color: #0284c7;
    }
    .sound-btn:active {
      background: #e2e8f0;
    }

    /* Shockwave ring animations */
    .shockwave-ring {
      transform-origin: 300px 290px;
      animation: pulseWave 2.2s cubic-bezier(0.1, 0.8, 0.3, 1) infinite;
    }
    .shockwave-ring:nth-child(2) { animation-delay: 0.55s; }
    .shockwave-ring:nth-child(3) { animation-delay: 1.1s; }
    .shockwave-ring:nth-child(4) { animation-delay: 1.65s; }

    @keyframes pulseWave {
      0% { r: 12px; opacity: 0.95; stroke-width: 3px; }
      100% { r: 85px; opacity: 0; stroke-width: 0.5px; }
    }

    /* Flame flicker */
    .flame-spark {
      animation: flicker 0.9s ease-in-out infinite alternate;
      transform-origin: 300px 76px;
    }
    @keyframes flicker {
      0% { opacity: 0.82; }
      100% { opacity: 1; }
    }
  </style>
</head>
<body>

  <div class="diagram-wrap">
    <svg viewBox="0 0 600 375" xmlns="http://www.w3.org/2000/svg">
      <defs>
        
        <marker id="arrow" viewBox="0 0 10 10" refX="6" 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="#1e2945"/>
        </marker>
        <marker id="arrow-blue" viewBox="0 0 10 10" refX="6" 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="#0284c7"/>
        </marker>

        
        <radialGradient id="heatGlow" cx="50%" cy="50%" r="50%">
          <stop offset="0%" stop-color="#fbbf24" stop-opacity="0.9"/>
          <stop offset="55%" stop-color="#f97316" stop-opacity="0.4"/>
          <stop offset="100%" stop-color="#ef4444" stop-opacity="0"/>
        </radialGradient>
        <radialGradient id="acousticCenter" cx="50%" cy="50%" r="50%">
          <stop offset="0%" stop-color="#0284c7" stop-opacity="0.6"/>
          <stop offset="70%" stop-color="#38bdf8" stop-opacity="0.15"/>
          <stop offset="100%" stop-color="#38bdf8" stop-opacity="0"/>
        </radialGradient>
      </defs>

      
      <g id="group-reactants">
        
        <text x="125" y="28" font-size="15" font-weight="700" fill="#1e2945" text-anchor="middle">Reactants: 2H₂ + O₂</text>

        
        <g id="h2-1" transform="translate(62, 70)">
          <line x1="0" y1="0" x2="28" y2="0" stroke="#94a3b8" stroke-width="3"/>
          <circle cx="0" cy="0" r="14" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="0" y="5" font-size="13" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
          <circle cx="28" cy="0" r="14" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="28" y="5" font-size="13" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
        </g>

        
        <g id="h2-2" transform="translate(62, 134)">
          <line x1="0" y1="0" x2="28" y2="0" stroke="#94a3b8" stroke-width="3"/>
          <circle cx="0" cy="0" r="14" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="0" y="5" font-size="13" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
          <circle cx="28" cy="0" r="14" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="28" y="5" font-size="13" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
        </g>

        
        <text x="132" y="108" font-size="22" font-weight="700" fill="#64748b" text-anchor="middle">+</text>

        
        <g id="o2" transform="translate(182, 102)">
          <line x1="0" y1="-15" x2="0" y2="15" stroke="#cbd5e1" stroke-width="4"/>
          <circle cx="0" cy="-16" r="17" fill="#fee2e2" stroke="#dc2626" stroke-width="2"/>
          <text x="0" y="-11" font-size="13" font-weight="bold" fill="#b91c1c" text-anchor="middle">O</text>
          <circle cx="0" cy="16" r="17" fill="#fee2e2" stroke="#dc2626" stroke-width="2"/>
          <text x="0" y="21" font-size="13" font-weight="bold" fill="#b91c1c" text-anchor="middle">O</text>
        </g>
      </g>

      
      <g id="center-reaction">
        <circle cx="300" cy="74" r="28" fill="url(#heatGlow)" class="flame-spark"/>
        <path d="M 300 58 C 293 69, 289 77, 293 86 C 297 92, 303 92, 307 86 C 311 77, 307 69, 300 58 Z" fill="#f59e0b" stroke="#d97706" stroke-width="1.5" class="flame-spark"/>
        <path d="M 300 68 C 297 74, 295 78, 297 83 C 299 86, 302 86, 304 83 C 306 78, 303 74, 300 68 Z" fill="#fef08a"/>

        <line x1="248" y1="102" x2="344" y2="102" stroke="#1e2945" stroke-width="2.5" marker-end="url(#arrow)"/>
        <text x="300" y="122" font-size="12" font-weight="700" fill="#dc2626" text-anchor="middle">+ Heat Energy</text>
      </g>

      
      <g id="group-products">
        
        <text x="475" y="28" font-size="15" font-weight="700" fill="#1e2945" text-anchor="middle">Products: 2H₂O (Water)</text>

        
        <g id="h2o-1" transform="translate(426, 94)">
          
          <line x1="0" y1="-8" x2="-28" y2="24" stroke="#94a3b8" stroke-width="3"/>
          <line x1="0" y1="-8" x2="28" y2="24" stroke="#94a3b8" stroke-width="3"/>

          
          <path d="M -13 8 A 18 18 0 0 0 13 8" fill="none" stroke="#64748b" stroke-width="1.2" stroke-dasharray="2 2"/>
          <text x="0" y="22" font-size="10" font-weight="700" fill="#475569" text-anchor="middle">104.5°</text>

          
          <circle cx="0" cy="-8" r="16" fill="#fee2e2" stroke="#dc2626" stroke-width="2"/>
          <text x="0" y="-3" font-size="13" font-weight="bold" fill="#b91c1c" text-anchor="middle">O</text>

          
          <circle cx="-28" cy="24" r="12" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="-28" y="28" font-size="11" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
          <circle cx="28" cy="24" r="12" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="28" y="28" font-size="11" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
        </g>

        
        <g id="h2o-2" transform="translate(524, 94)">
          
          <line x1="0" y1="-8" x2="-28" y2="24" stroke="#94a3b8" stroke-width="3"/>
          <line x1="0" y1="-8" x2="28" y2="24" stroke="#94a3b8" stroke-width="3"/>

          
          <path d="M -13 8 A 18 18 0 0 0 13 8" fill="none" stroke="#64748b" stroke-width="1.2" stroke-dasharray="2 2"/>
          <text x="0" y="22" font-size="10" font-weight="700" fill="#475569" text-anchor="middle">104.5°</text>

          
          <circle cx="0" cy="-8" r="16" fill="#fee2e2" stroke="#dc2626" stroke-width="2"/>
          <text x="0" y="-3" font-size="13" font-weight="bold" fill="#b91c1c" text-anchor="middle">O</text>

          
          <circle cx="-28" cy="24" r="12" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="-28" y="28" font-size="11" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
          <circle cx="28" cy="24" r="12" fill="#e0f2fe" stroke="#0284c7" stroke-width="2"/>
          <text x="28" y="28" font-size="11" font-weight="bold" fill="#0369a1" text-anchor="middle">H</text>
        </g>
      </g>

      
      <line x1="40" y1="188" x2="560" y2="188" stroke="#e2e8f0" stroke-width="1" stroke-dasharray="6 4"/>

      
      <g id="shockwave-section">
        
        <text x="300" y="214" font-size="14" font-weight="700" fill="#1e2945" text-anchor="middle">Rapid Thermal Expansion of Air</text>
        <text x="300" y="366" font-size="12" font-weight="600" fill="#0369a1" text-anchor="middle">Acoustic Shockwave ("Squeaky Pop" Sound)</text>

        
        <circle cx="300" cy="286" r="32" fill="url(#acousticCenter)"/>
        
        
        <g>
          <circle cx="300" cy="286" r="24" fill="none" stroke="#0284c7" class="shockwave-ring"/>
          <circle cx="300" cy="286" r="44" fill="none" stroke="#0ea5e9" class="shockwave-ring"/>
          <circle cx="300" cy="286" r="64" fill="none" stroke="#38bdf8" class="shockwave-ring"/>
          <circle cx="300" cy="286" r="82" fill="none" stroke="#7dd3fc" class="shockwave-ring"/>
        </g>

        
        <g stroke="#0284c7" stroke-width="1.8" marker-end="url(#arrow-blue)" opacity="0.8">
          <line x1="264" y1="286" x2="216" y2="286"/>
          <line x1="336" y1="286" x2="384" y2="286"/>
          <line x1="274" y1="262" x2="236" y2="238"/>
          <line x1="326" y1="262" x2="364" y2="238"/>
          <line x1="274" y1="310" x2="236" y2="334"/>
          <line x1="326" y1="310" x2="364" y2="334"/>
        </g>

        
        <circle cx="300" cy="286" r="7" fill="#0284c7"/>
        <circle cx="300" cy="286" r="3" fill="#ffffff"/>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <button class="step-btn active" id="btnAll" onclick="setMode('all')">Full Reaction</button>
    <button class="step-btn" id="btnReactants" onclick="setMode('reactants')">Reactants</button>
    <button class="step-btn" id="btnProducts" onclick="setMode('products')">Products</button>
    <button class="sound-btn" onclick="playSqueakPop()">Play Pop 🔊</button>
  </div>

  <script>
    function setMode(mode) {
      const reactants = document.getElementById('group-reactants');
      const products = document.getElementById('group-products');
      const shockwave = document.getElementById('shockwave-section');
      const center = document.getElementById('center-reaction');

      document.querySelectorAll('.step-btn').forEach(b => b.classList.remove('active'));

      if (mode === 'reactants') {
        document.getElementById('btnReactants').classList.add('active');
        reactants.style.opacity = '1';
        products.style.opacity = '0.2';
        center.style.opacity = '0.25';
        shockwave.style.opacity = '0.25';
      } else if (mode === 'products') {
        document.getElementById('btnProducts').classList.add('active');
        reactants.style.opacity = '0.2';
        products.style.opacity = '1';
        center.style.opacity = '1';
        shockwave.style.opacity = '1';
        playSqueakPop();
      } else {
        document.getElementById('btnAll').classList.add('active');
        reactants.style.opacity = '1';
        products.style.opacity = '1';
        center.style.opacity = '1';
        shockwave.style.opacity = '1';
      }
    }

    function playSqueakPop() {
      try {
        const AudioCtx = window.AudioContext || window.webkitAudioContext;
        if (!AudioCtx) return;
        const ctx = new AudioCtx();
        
        // 1. Initial High Squeak (rapid frequency sweep)
        const osc = ctx.createOscillator();
        const gain = ctx.createGain();
        osc.type = 'sine';
        
        const now = ctx.currentTime;
        osc.frequency.setValueAtTime(650, now);
        osc.frequency.exponentialRampToValueAtTime(1950, now + 0.07);
        osc.frequency.exponentialRampToValueAtTime(320, now + 0.16);

        gain.gain.setValueAtTime(0.25, now);
        gain.gain.exponentialRampToValueAtTime(0.001, now + 0.2);

        osc.connect(gain);
        gain.connect(ctx.destination);

        // 2. Pop "Thump" burst
        const popOsc = ctx.createOscillator();
        const popGain = ctx.createGain();
        popOsc.type = 'triangle';
        popOsc.frequency.setValueAtTime(220, now + 0.05);
        popOsc.frequency.exponentialRampToValueAtTime(45, now + 0.18);

        popGain.gain.setValueAtTime(0.35, now + 0.05);
        popGain.gain.exponentialRampToValueAtTime(0.001, now + 0.22);

        popOsc.connect(popGain);
        popGain.connect(ctx.destination);

        osc.start(now);
        osc.stop(now + 0.2);
        popOsc.start(now + 0.05);
        popOsc.stop(now + 0.22);
      } catch (e) {}
    }
  </script>
</body>
</html>

Testing for Hydrogen: The Squeaky Pop Test

<!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: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    }
    body {
      background: #ffffff;
      color: #1e2945;
      padding: 14px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      justify-content: center;
      min-height: 100%;
    }
    .header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      margin-bottom: 2px;
    }
    .title {
      font-size: 13px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.6px;
      color: #64748b;
    }
    .sound-btn {
      background: #f0fdf4;
      border: 1px solid #86efac;
      color: #166534;
      border-radius: 20px;
      padding: 3px 10px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 4px;
      transition: background 0.2s, box-shadow 0.2s;
    }
    .sound-btn:active {
      background: #dcfce7;
      box-shadow: 0 0 0 2px rgba(34, 197, 94, 0.2);
    }
    .exam-card {
      background: #ffffff;
      border: 1.5px solid #e6e6e6;
      border-radius: 10px;
      padding: 12px 14px;
      position: relative;
      box-shadow: 0 1px 3px rgba(0,0,0,0.03);
    }
    .card-good {
      border-color: #22c55e;
      background: #fcfdfc;
    }
    .card-bad {
      border-color: #f87171;
      background: #fffdfd;
    }
    .card-header {
      display: flex;
      align-items: center;
      gap: 8px;
      margin-bottom: 8px;
    }
    .badge {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      width: 22px;
      height: 22px;
      border-radius: 50%;
      font-size: 13px;
      font-weight: 700;
      color: #ffffff;
      flex-shrink: 0;
    }
    .badge-good {
      background: #16a34a;
    }
    .badge-bad {
      background: #dc2626;
    }
    .badge-title {
      font-size: 14px;
      font-weight: 700;
    }
    .card-good .badge-title {
      color: #15803d;
    }
    .card-bad .badge-title {
      color: #b91c1c;
    }
    .points-tag {
      margin-left: auto;
      font-size: 11px;
      font-weight: 700;
      padding: 2px 7px;
      border-radius: 6px;
    }
    .points-good {
      background: #dcfce7;
      color: #15803d;
    }
    .points-bad {
      background: #fee2e2;
      color: #b91c1c;
    }
    .row {
      display: flex;
      margin-bottom: 6px;
      font-size: 13px;
      line-height: 1.45;
      align-items: baseline;
    }
    .row:last-child {
      margin-bottom: 0;
    }
    .label {
      width: 58px;
      flex-shrink: 0;
      font-weight: 700;
      color: #64748b;
      font-size: 12px;
      text-transform: uppercase;
      letter-spacing: 0.3px;
    }
    .content {
      color: #1e2945;
      flex-grow: 1;
    }
    .tag-highlight {
      background: #dcfce7;
      color: #14532d;
      font-weight: 700;
      padding: 1px 5px;
      border-radius: 4px;
      border: 1px solid #86efac;
      white-space: nowrap;
    }
    .tag-strike {
      background: #fee2e2;
      color: #7f1d1d;
      text-decoration: line-through;
      padding: 1px 5px;
      border-radius: 4px;
      border: 1px solid #fca5a5;
      white-space: nowrap;
    }
    .reason {
      font-size: 11px;
      color: #dc2626;
      font-style: italic;
      display: block;
      margin-top: 1px;
    }
  </style>
</head>
<body>
  <div class="header">
    <span class="title">GCSE Exam Mark Scheme</span>
    <button class="sound-btn" id="squeakBtn" onclick="playSqueak()">🔊 Test Pop</button>
  </div>

  
  <div class="exam-card card-good">
    <div class="card-header">
      <span class="badge badge-good">✓</span>
      <span class="badge-title">Full Marks Answer</span>
      <span class="points-tag points-good">2 / 2 MARKS</span>
    </div>
    <div class="row">
      <span class="label">Test:</span>
      <span class="content">Hold a <span class="tag-highlight">burning / lit splint</span> at the <span class="tag-highlight">mouth</span> of the test tube.</span>
    </div>
    <div class="row">
      <span class="label">Result:</span>
      <span class="content">Burns with a <span class="tag-highlight">squeaky pop</span>.</span>
    </div>
  </div>

  
  <div class="exam-card card-bad">
    <div class="card-header">
      <span class="badge badge-bad">✗</span>
      <span class="badge-title">Zero Marks (Common Pitfalls)</span>
      <span class="points-tag points-bad">0 / 2 MARKS</span>
    </div>
    <div class="row">
      <span class="label">Test:</span>
      <div class="content">
        Put a <span class="tag-strike">glowing splint</span> / flame <span class="tag-strike">inside</span>.
        <span class="reason">Glowing splint is for O₂; inside extinguishes flame.</span>
      </div>
    </div>
    <div class="row">
      <span class="label">Result:</span>
      <div class="content">
        It <span class="tag-strike">pops</span> / <span class="tag-strike">makes a noise</span>.
        <span class="reason">Must specify "squeaky pop" or hydrogen combustion.</span>
      </div>
    </div>
  </div>

  <script>
    function playSqueak() {
      try {
        const AudioContext = window.AudioContext || window.webkitAudioContext;
        const ctx = new AudioContext();

        // 1. High-frequency squeak chirp (sweeping downwards fast)
        const osc = ctx.createOscillator();
        const gain = ctx.createGain();

        osc.type = 'sine';
        osc.frequency.setValueAtTime(1400, ctx.currentTime);
        osc.frequency.exponentialRampToValueAtTime(550, ctx.currentTime + 0.12);

        gain.gain.setValueAtTime(0.01, ctx.currentTime);
        gain.gain.linearRampToValueAtTime(0.3, ctx.currentTime + 0.02);
        gain.gain.exponentialRampToValueAtTime(0.001, ctx.currentTime + 0.16);

        osc.connect(gain);
        gain.connect(ctx.destination);

        // 2. Mini pop / burst thump
        const popOsc = ctx.createOscillator();
        const popGain = ctx.createGain();

        popOsc.type = 'triangle';
        popOsc.frequency.setValueAtTime(220, ctx.currentTime);
        popOsc.frequency.exponentialRampToValueAtTime(70, ctx.currentTime + 0.1);

        popGain.gain.setValueAtTime(0.25, ctx.currentTime + 0.01);
        popGain.gain.exponentialRampToValueAtTime(0.001, ctx.currentTime + 0.12);

        popOsc.connect(popGain);
        popGain.connect(ctx.destination);

        osc.start(ctx.currentTime);
        osc.stop(ctx.currentTime + 0.18);

        popOsc.start(ctx.currentTime);
        popOsc.stop(ctx.currentTime + 0.14);

        const btn = document.getElementById('squeakBtn');
        btn.textContent = '🔥 *POP!*';
        setTimeout(() => {
          btn.textContent = '🔊 Test Pop';
        }, 800);
      } catch (e) {}
    }
  </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%;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: transparent;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 12px 8px;
      user-select: none;
    }

    .nav-tabs {
      display: flex;
      gap: 6px;
      margin-bottom: 12px;
      width: 100%;
      max-width: 350px;
    }

    .tab-btn {
      flex: 1;
      border: 1px solid #e6e6e6;
      background: #f8fafc;
      color: #64748b;
      padding: 6px 4px;
      border-radius: 6px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      text-align: center;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
    }

    .tab-btn.active {
      background: #ffffff;
      color: #3b82f6;
      border-color: #3b82f6;
      box-shadow: 0 1px 3px rgba(59, 130, 246, 0.15);
    }

    .scene-wrap {
      position: relative;
      width: 100%;
      max-width: 350px;
      height: 250px;
      background: #ffffff;
      border: 1px solid #e6e6e6;
      border-radius: 10px;
      overflow: hidden;
    }

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

    .controls {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      max-width: 350px;
      margin-top: 10px;
      padding: 0 4px;
    }

    .ctrl-btn {
      background: #ffffff;
      border: 1px solid #e6e6e6;
      color: #1e2945;
      padding: 6px 14px;
      border-radius: 6px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 5px;
    }
    .ctrl-btn:hover { background: #f8fafc; }
    .ctrl-btn:active { background: #f1f5f9; }

    .sound-btn {
      color: #d97706;
      border-color: #fde68a;
      background: #fffbeb;
    }
    .sound-btn:hover { background: #fef3c7; }

    /* Visual Transitions */
    .fade-item {
      transition: opacity 0.35s ease, transform 0.35s ease;
    }

    .splint-group {
      transition: transform 0.4s ease, opacity 0.3s ease;
    }
  </style>
</head>
<body>

  
  <div class="nav-tabs">
    <button class="tab-btn active" onclick="setStep(0)">1. Trap H₂</button>
    <button class="tab-btn" onclick="setStep(1)">2. Lit Splint</button>
    <button class="tab-btn" onclick="setStep(2)">3. Pop!</button>
  </div>

  
  <div class="scene-wrap">
    <svg viewBox="0 0 350 250">
      <defs>
        
        <linearGradient id="glassGrad" x1="0" y1="0" x2="1" y2="0">
          <stop offset="0%" stop-color="#3b82f6" stop-opacity="0.15"/>
          <stop offset="30%" stop-color="#3b82f6" stop-opacity="0.05"/>
          <stop offset="70%" stop-color="#3b82f6" stop-opacity="0.02"/>
          <stop offset="100%" stop-color="#3b82f6" stop-opacity="0.2"/>
        </linearGradient>

        
        <radialGradient id="flameGrad" cx="40%" cy="60%" r="60%">
          <stop offset="0%" stop-color="#ffffff"/>
          <stop offset="40%" stop-color="#fef08a"/>
          <stop offset="75%" stop-color="#f59e0b"/>
          <stop offset="100%" stop-color="#ea580c"/>
        </radialGradient>

        
        <radialGradient id="burstGrad" cx="50%" cy="50%" r="50%">
          <stop offset="20%" stop-color="#ffffff"/>
          <stop offset="60%" stop-color="#fef08a"/>
          <stop offset="90%" stop-color="#f59e0b"/>
          <stop offset="100%" stop-color="#f97316"/>
        </radialGradient>
      </defs>

      
      <line x1="20" y1="230" x2="330" y2="230" stroke="#f1f5f9" stroke-width="2"/>

      
      <g id="tubeGroup" transform="translate(145, 18)">
        
        <path d="M 6,32 Q 30,10 54,32 L 54,145 L 6,145 Z" fill="#eff6ff"/>
        
        
        <g id="gasContent" class="fade-item" opacity="1">
          <circle cx="20" cy="50" r="3" fill="#60a5fa" opacity="0.6"/>
          <circle cx="40" cy="65" r="4" fill="#60a5fa" opacity="0.6"/>
          <circle cx="25" cy="85" r="3.5" fill="#60a5fa" opacity="0.6"/>
          <circle cx="38" cy="110" r="2.5" fill="#60a5fa" opacity="0.6"/>
          <circle cx="18" cy="125" r="3" fill="#60a5fa" opacity="0.6"/>
          
          <text x="30" y="70" text-anchor="middle" font-size="14" font-weight="700" fill="#1e40af">H₂ Gas</text>
          <text x="30" y="88" text-anchor="middle" font-size="11" font-weight="600" fill="#64748b">(less dense)</text>
          
          <path d="M 30,132 L 30,108 M 26,113 L 30,107 L 34,113" stroke="#3b82f6" stroke-width="2" fill="none" stroke-linecap="round"/>
        </g>

        
        <path d="M 5,30 Q 30,4 55,30 L 55,150 L 5,150 Z" 
              fill="url(#glassGrad)" stroke="#94a3b8" stroke-width="2"/>
        
        <ellipse cx="30" cy="150" rx="27" ry="5" fill="#f8fafc" stroke="#94a3b8" stroke-width="2"/>
        
        
        <path d="M 12,35 Q 30,18 48,35" stroke="#ffffff" stroke-width="2" fill="none" opacity="0.8"/>
        <line x1="10" y1="45" x2="10" y2="140" stroke="#ffffff" stroke-width="2" opacity="0.6"/>

        
        <g id="droplets" class="fade-item" opacity="0">
          <circle cx="14" cy="138" r="2.5" fill="#38bdf8" stroke="#0284c7" stroke-width="0.8"/>
          <circle cx="22" cy="144" r="2" fill="#38bdf8" stroke="#0284c7" stroke-width="0.8"/>
          <circle cx="38" cy="142" r="3" fill="#38bdf8" stroke="#0284c7" stroke-width="0.8"/>
          <circle cx="46" cy="136" r="2.5" fill="#38bdf8" stroke="#0284c7" stroke-width="0.8"/>
          <text x="75" y="142" font-size="12" font-weight="600" fill="#0284c7">H₂O droplets</text>
          <path d="M 68,138 L 52,140" stroke="#0284c7" stroke-width="1.5" fill="none" stroke-linecap="round"/>
        </g>
      </g>

      
      <g id="tubeLabel" class="fade-item" opacity="1" transform="translate(42, 45)">
        <rect x="0" y="0" width="94" height="38" rx="6" fill="#f8fafc" stroke="#e2e8f0" stroke-width="1"/>
        <text x="47" y="16" text-anchor="middle" font-size="11" font-weight="700" fill="#1e2945">Inverted Tube</text>
        <text x="47" y="30" text-anchor="middle" font-size="10" fill="#64748b">Traps light gas</text>
        <line x1="94" y1="20" x2="142" y2="35" stroke="#94a3b8" stroke-width="1" stroke-dasharray="2 2"/>
      </g>

      
      <g id="splintGroup" class="splint-group" transform="translate(10, 215) rotate(-15)">
        
        <rect x="0" y="-4" width="130" height="8" rx="2" fill="#d97706" stroke="#b45309" stroke-width="1"/>
        
        <rect x="120" y="-4" width="10" height="8" rx="1" fill="#451a03"/>
        
        
        <g id="flame" transform="translate(130, 0)">
          
          <circle cx="6" cy="0" r="14" fill="#f59e0b" opacity="0.25"/>
          
          <path d="M 0,-6 Q 8,-12 14,0 Q 8,12 0,6 Z" fill="url(#flameGrad)" transform="rotate(-90 6 0)"/>
        </g>

        
        <g id="splintLabel" transform="translate(20, -18)">
          <text x="35" y="0" text-anchor="middle" font-size="12" font-weight="700" fill="#b45309">Lit splint</text>
        </g>
      </g>

      
      <g id="popBurst" class="fade-item" opacity="0" transform="translate(175, 172)">
        
        <polygon points="0,-32 10,-12 32,-18 18,-2 35,14 14,14 18,34 0,20 -18,34 -14,14 -35,14 -18,-2 -32,-18 -10,-12"
                 fill="url(#burstGrad)" stroke="#ea580c" stroke-width="2"/>
        
        
        <line x1="-36" y1="-28" x2="-46" y2="-36" stroke="#f59e0b" stroke-width="2" stroke-linecap="round"/>
        <line x1="36" y1="-28" x2="46" y2="-36" stroke="#f59e0b" stroke-width="2" stroke-linecap="round"/>
        <line x1="40" y1="24" x2="50" y2="30" stroke="#f59e0b" stroke-width="2" stroke-linecap="round"/>
        <line x1="-40" y1="24" x2="-50" y2="30" stroke="#f59e0b" stroke-width="2" stroke-linecap="round"/>

        
        <text x="0" y="5" text-anchor="middle" font-size="13" font-weight="900" fill="#7c2d12" letter-spacing="0.5">SQUEAKY POP!</text>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <button class="ctrl-btn" id="prevBtn" onclick="prevStep()">← Back</button>
    <button class="ctrl-btn sound-btn" id="soundBtn" onclick="playPopSound()">🔊 Pop Sound</button>
    <button class="ctrl-btn" id="nextBtn" onclick="nextStep()">Next →</button>
  </div>

  <script>
    let currentStep = 0;
    const totalSteps = 3;

    // Web Audio Squeaky Pop Synthesizer
    function playPopSound() {
      try {
        const ctx = new (window.AudioContext || window.webkitAudioContext)();
        const osc = ctx.createOscillator();
        const gain = ctx.createGain();

        osc.type = 'triangle';
        // Classic high-pitched squeak rising then rapid burst drop
        osc.frequency.setValueAtTime(500, ctx.currentTime);
        osc.frequency.exponentialRampToValueAtTime(1750, ctx.currentTime + 0.07);
        osc.frequency.exponentialRampToValueAtTime(320, ctx.currentTime + 0.16);

        gain.setValueAtTime(0.35, ctx.currentTime);
        gain.exponentialRampToValueAtTime(0.001, ctx.currentTime + 0.18);

        osc.connect(gain);
        gain.connect(ctx.destination);

        osc.start();
        osc.stop(ctx.currentTime + 0.2);
      } catch (e) {
        // Fallback gracefully if Web Audio is blocked
      }
    }

    function setStep(step) {
      currentStep = step;

      // Update Tab Buttons
      const tabs = document.querySelectorAll('.tab-btn');
      tabs.forEach((t, i) => t.classList.toggle('active', i === step));

      // Elements
      const splint = document.getElementById('splintGroup');
      const popBurst = document.getElementById('popBurst');
      const droplets = document.getElementById('droplets');
      const gasContent = document.getElementById('gasContent');
      const flame = document.getElementById('flame');

      if (step === 0) {
        // Step 1: Rest position, trapped gas
        splint.style.transform = 'translate(-40px, 220px) rotate(-15deg)';
        splint.style.opacity = '0.3';
        popBurst.style.opacity = '0';
        droplets.style.opacity = '0';
        gasContent.style.opacity = '1';
        flame.style.opacity = '1';
      } else if (step === 1) {
        // Step 2: Lit splint brought to rim
        splint.style.transform = 'translate(25px, 175px) rotate(-10deg)';
        splint.style.opacity = '1';
        popBurst.style.opacity = '0';
        droplets.style.opacity = '0';
        gasContent.style.opacity = '0.7';
        flame.style.opacity = '1';
      } else if (step === 2) {
        // Step 3: Ignition, Squeaky Pop & Droplets
        splint.style.transform = 'translate(25px, 175px) rotate(-10deg)';
        splint.style.opacity = '1';
        popBurst.style.opacity = '1';
        droplets.style.opacity = '1';
        gasContent.style.opacity = '0.15';
        flame.style.opacity = '0.5';
        playPopSound();
      }

      // Update button text / states
      document.getElementById('prevBtn').disabled = (step === 0);
      document.getElementById('prevBtn').style.opacity = step === 0 ? '0.4' : '1';
      document.getElementById('nextBtn').textContent = step === totalSteps - 1 ? '↺ Restart' : 'Next →';
    }

    function nextStep() {
      if (currentStep >= totalSteps - 1) {
        setStep(0);
      } else {
        setStep(currentStep + 1);
      }
    }

    function prevStep() {
      if (currentStep > 0) {
        setStep(currentStep - 1);
      }
    }

    // Initialize Step 1
    setStep(0);
  </script>
</body>
</html>

UK-GCSE-SCIENCE-CHEM-CC-02

Child standards (1)

Aligned learning resources

Related diagrams