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

    body {
      width: 100%;
      min-height: 100%;
      background: #f8fafc;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 8px;
    }

    .container {
      width: 100%;
      max-width: 680px;
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
    }

    @media (max-width: 520px) {
      .container {
        grid-template-columns: 1fr;
        max-width: 340px;
        gap: 12px;
      }
    }

    .panel {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px 8px 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      transition: border-color 0.2s ease, box-shadow 0.2s ease;
    }

    .panel:hover {
      border-color: #cbd5e1;
      box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
    }

    .panel-header {
      width: 100%;
      display: flex;
      align-items: center;
      gap: 8px;
      margin-bottom: 4px;
      padding: 0 4px;
    }

    .badge {
      width: 22px;
      height: 22px;
      border-radius: 6px;
      background: #f1f5f9;
      color: #475569;
      font-size: 11px;
      font-weight: 700;
      display: flex;
      align-items: center;
      justify-content: center;
      flex-shrink: 0;
    }

    .panel-title {
      font-size: 12.5px;
      font-weight: 700;
      color: #1e2945;
      line-height: 1.2;
    }

    .panel-svg {
      width: 100%;
      height: auto;
      max-height: 155px;
      display: block;
      margin: 2px 0 8px;
    }

    .status-tag {
      font-size: 10.5px;
      font-weight: 700;
      padding: 4px 10px;
      border-radius: 9999px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      text-align: center;
      line-height: 1.2;
      width: fit-content;
    }

    .status-neutral {
      background: #eff6ff;
      color: #2563eb;
      border: 1px solid #dbeafe;
    }

    .status-success {
      background: #dcfce7;
      color: #15803d;
      border: 1px solid #bbf7d0;
    }

    .status-error {
      background: #fee2e2;
      color: #b91c1c;
      border: 1px solid #fecaca;
    }

    /* SVG shapes & typography */
    .enzyme-shape {
      fill: #eff6ff;
      stroke: #3b82f6;
      stroke-width: 2;
      stroke-linejoin: round;
    }

    .substrate-match {
      fill: #ecfdf5;
      stroke: #10b981;
      stroke-width: 2;
      stroke-linejoin: round;
    }

    .substrate-mismatch {
      fill: #fef2f2;
      stroke: #ef4444;
      stroke-width: 2;
      stroke-linejoin: round;
    }

    .arrow-guide {
      stroke: #94a3b8;
      stroke-width: 1.75;
      stroke-dasharray: 3 3;
      fill: none;
      marker-end: url(#arrowhead);
    }

    .svg-label-blue {
      font-size: 9.5px;
      font-weight: 700;
      fill: #2563eb;
      text-anchor: middle;
      font-family: inherit;
    }

    .svg-label-green {
      font-size: 9px;
      font-weight: 700;
      fill: #059669;
      text-anchor: middle;
      font-family: inherit;
    }

    .svg-label-red {
      font-size: 9px;
      font-weight: 700;
      fill: #dc2626;
      text-anchor: middle;
      font-family: inherit;
    }
  </style>
</head>
<body>

  <div class="container">
    
    <div class="panel">
      <div class="panel-header">
        <div class="badge">A</div>
        <div class="panel-title">Shape Recognition</div>
      </div>
      
      <svg class="panel-svg" viewBox="0 0 170 150" xmlns="http://www.w3.org/2000/svg">
        <defs>
          <marker id="arrowhead" markerWidth="5" markerHeight="5" refX="3.5" refY="2.5" orient="auto">
            <polygon points="0 0, 5 2.5, 0 5" fill="#94a3b8" />
          </marker>
        </defs>

        
        <path class="substrate-match" d="
          M 24,14
          h 122
          a 6,6 0 0 1 6,6
          v 18
          h -26
          L 110,54
          L 94,38
          h -18
          v 16
          h -32
          v -16
          h -26
          v -18
          a 6,6 0 0 1 6,-6
          Z
        " />
        <text x="85" y="29" class="svg-label-green">Matching Substrate</text>

        
        <line x1="85" y1="58" x2="85" y2="72" class="arrow-guide" />

        
        <path class="enzyme-shape" d="
          M 18,78
          h 26
          v 16
          h 32
          v -16
          h 18
          l 16,16
          l 16,-16
          h 26
          a 6,6 0 0 1 6,6
          v 48
          a 6,6 0 0 1 -6,6
          h -134
          a 6,6 0 0 1 -6,-6
          v -48
          a 6,6 0 0 1 6,-6
          Z
        " />
        <text x="85" y="118" class="svg-label-blue">Rigid Active Site</text>
      </svg>

      <span class="status-tag status-neutral">Rigid Active Site</span>
    </div>

    
    <div class="panel">
      <div class="panel-header">
        <div class="badge">B</div>
        <div class="panel-title">Perfect Fit</div>
      </div>

      <svg class="panel-svg" viewBox="0 0 170 150" xmlns="http://www.w3.org/2000/svg">
        
        <path class="enzyme-shape" d="
          M 18,78
          h 26
          v 16
          h 32
          v -16
          h 18
          l 16,16
          l 16,-16
          h 26
          a 6,6 0 0 1 6,6
          v 48
          a 6,6 0 0 1 -6,6
          h -134
          a 6,6 0 0 1 -6,-6
          v -48
          a 6,6 0 0 1 6,-6
          Z
        " />

        
        <path class="substrate-match" d="
          M 24,54
          h 122
          a 6,6 0 0 1 6,6
          v 18
          h -26
          L 110,94
          L 94,78
          h -18
          v 16
          h -32
          v -16
          h -26
          v -18
          a 6,6 0 0 1 6,-6
          Z
        " />
        
        <text x="85" y="69" class="svg-label-green">Substrate Docked</text>
        <text x="85" y="118" class="svg-label-blue">Zero Shape Change</text>
      </svg>

      <span class="status-tag status-success">✓ Matching Substrate (Fits)</span>
    </div>

    
    <div class="panel">
      <div class="panel-header">
        <div class="badge">C</div>
        <div class="panel-title">Shape Mismatch</div>
      </div>

      <svg class="panel-svg" viewBox="0 0 170 150" xmlns="http://www.w3.org/2000/svg">
        
        <path class="substrate-mismatch" d="
          M 24,14
          h 122
          a 6,6 0 0 1 6,6
          v 12
          c 0,16 -24,16 -32,2
          c -8,14 -28,14 -36,0
          c -8,14 -28,14 -36,0
          c -8,14 -24,14 -30,0
          v -14
          a 6,6 0 0 1 6,-6
          Z
        " />
        <text x="85" y="28" class="svg-label-red">Non-matching Substrate</text>

        
        <g stroke="#ef4444" stroke-width="2" stroke-linecap="round">
          <line x1="50" y1="56" x2="60" y2="66" />
          <line x1="60" y1="56" x2="50" y2="66" />
          <line x1="110" y1="56" x2="120" y2="66" />
          <line x1="120" y1="56" x2="110" y2="66" />
        </g>

        
        <path class="enzyme-shape" d="
          M 18,78
          h 26
          v 16
          h 32
          v -16
          h 18
          l 16,16
          l 16,-16
          h 26
          a 6,6 0 0 1 6,6
          v 48
          a 6,6 0 0 1 -6,6
          h -134
          a 6,6 0 0 1 -6,-6
          v -48
          a 6,6 0 0 1 6,-6
          Z
        " />
        <text x="85" y="118" class="svg-label-blue">Rigid Active Site</text>
      </svg>

      <span class="status-tag status-error">✗ Non-matching (No Reaction)</span>
    </div>
  </div>

</body>
</html>

Enzyme Structure and the Active Site Model

<!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;
      gap: 10px;
      user-select: none;
    }

    /* Stepper Controls */
    .controls {
      display: flex;
      align-items: center;
      gap: 8px;
      width: 100%;
      max-width: 540px;
      justify-content: center;
      flex-wrap: wrap;
    }

    .step-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      padding: 6px 14px;
      font-size: 13px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      transition: all 0.25s ease;
    }

    .step-btn.active {
      background: #22b7ff;
      color: #ffffff;
      border-color: #0ea5e9;
      box-shadow: 0 2px 8px rgba(34, 183, 255, 0.3);
    }

    .play-btn {
      background: #1e2945;
      color: #ffffff;
      border: none;
      border-radius: 50%;
      width: 32px;
      height: 32px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 13px;
      cursor: pointer;
      transition: opacity 0.2s;
    }
    .play-btn:active { opacity: 0.8; }

    /* Comparison Area */
    .diagram-stage {
      width: 100%;
      max-width: 540px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .model-row {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 12px;
      display: flex;
      flex-direction: column;
      position: relative;
    }

    .row-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 2px;
    }

    .model-title {
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
    }

    .model-tag {
      font-size: 11px;
      font-weight: 600;
      padding: 2px 8px;
      border-radius: 10px;
      background: #f1f5f9;
      color: #64748b;
    }

    .model-tag.highlight {
      background: #e0f2fe;
      color: #0284c7;
    }

    .svg-container {
      width: 100%;
      height: 120px;
    }

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

    /* SVG Transitions */
    .smooth {
      transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1),
                  opacity 0.5s ease,
                  d 0.6s cubic-bezier(0.4, 0, 0.2, 1),
                  fill 0.4s ease,
                  stroke 0.4s ease;
    }

    .strain-pulse {
      animation: pulseGlow 1.2s infinite alternate ease-in-out;
    }

    @keyframes pulseGlow {
      from { stroke: #f59e0b; filter: drop-shadow(0 0 2px #f59e0b); }
      to { stroke: #d97706; filter: drop-shadow(0 0 6px #f59e0b); }
    }
  </style>
</head>
<body>

  
  <div class="controls">
    <button id="playToggle" class="play-btn" aria-label="Play/Pause">⏸</button>
    <button class="step-btn active" data-step="0">1. Initial contact</button>
    <button class="step-btn" data-step="1">2. Clamping</button>
    <button class="step-btn" data-step="2">3. Bond strain</button>
  </div>

  <div class="diagram-stage">
    
    <div class="model-row">
      <div class="row-header">
        <span class="model-title">Lock-and-Key</span>
        <span class="model-tag">Static Shape</span>
      </div>
      <div class="svg-container">
        <svg viewBox="0 0 400 120">
          <defs>
            <linearGradient id="lkEnzymeGrad" x1="0%" y1="0%" x2="0%" y2="100%">
              <stop offset="0%" stop-color="#93c5fd" />
              <stop offset="100%" stop-color="#60a5fa" />
            </linearGradient>
            <linearGradient id="subGrad" x1="0%" y1="0%" x2="0%" y2="100%">
              <stop offset="0%" stop-color="#fdba74" />
              <stop offset="100%" stop-color="#fb923c" />
            </linearGradient>
          </defs>

          
          <g id="lk-enzyme">
            <path d="M 40,110 L 360,110 Q 370,110 370,100 L 370,55 Q 370,45 360,45 L 260,45 L 260,80 L 140,80 L 140,45 L 40,45 Q 30,45 30,55 L 30,100 Q 30,110 40,110 Z" 
                  fill="url(#lkEnzymeGrad)" stroke="#3b82f6" stroke-width="2" />
            <text x="50" y="98" fill="#1e2945" font-size="12" font-weight="700">Enzyme</text>
            <text x="200" y="74" fill="#1e40af" font-size="11" font-weight="600" text-anchor="middle">Rigid Active Site</text>
          </g>

          
          <g id="lk-substrate" class="smooth" transform="translate(0, -32)">
            <rect x="144" y="44" width="112" height="32" rx="4" fill="url(#subGrad)" stroke="#ea580c" stroke-width="2" />
            
            <line x1="200" y1="45" x2="200" y2="75" stroke="#c2410c" stroke-width="2.5" stroke-dasharray="2 2" />
            <text x="200" y="38" fill="#9a3412" font-size="11" font-weight="700" text-anchor="middle">Substrate</text>
          </g>
        </svg>
      </div>
    </div>

    
    <div class="model-row">
      <div class="row-header">
        <span class="model-title">Induced-Fit</span>
        <span class="model-tag highlight">Conformational Change</span>
      </div>
      <div class="svg-container">
        <svg viewBox="0 0 400 120">
          <defs>
            <linearGradient id="ifEnzymeGrad" x1="0%" y1="0%" x2="0%" y2="100%">
              <stop offset="0%" stop-color="#7dd3fc" />
              <stop offset="100%" stop-color="#22b7ff" />
            </linearGradient>
            
            <filter id="amberGlow" x="-20%" y="-20%" width="140%" height="140%">
              <feDropShadow dx="0" dy="0" stdDeviation="3" flood-color="#f59e0b" flood-opacity="0.9" />
            </filter>
          </defs>

          
          <rect x="30" y="75" width="340" height="35" rx="8" fill="url(#ifEnzymeGrad)" stroke="#0284c7" stroke-width="2" />
          <text x="50" y="98" fill="#1e2945" font-size="12" font-weight="700">Enzyme</text>

          
          <path id="if-left-lobe" class="smooth" 
                d="M 30,80 L 30,45 Q 30,35 40,35 L 125,35 Q 135,35 135,45 L 135,80 Z" 
                fill="url(#ifEnzymeGrad)" stroke="#0284c7" stroke-width="2" />

          
          <path id="if-right-lobe" class="smooth" 
                d="M 265,80 L 265,45 Q 265,35 275,35 L 360,35 Q 370,35 370,45 L 370,80 Z" 
                fill="url(#ifEnzymeGrad)" stroke="#0284c7" stroke-width="2" />

          
          <g id="clamp-arrows" class="smooth" opacity="0">
            
            <path d="M 105,58 L 128,58 M 122,52 L 128,58 L 122,64" stroke="#0369a1" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round" />
            
            <path d="M 295,58 L 272,58 M 278,52 L 272,58 L 278,64" stroke="#0369a1" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round" />
          </g>

          
          <g id="if-substrate" class="smooth" transform="translate(0, -32)">
            
            <path id="if-sub-left" class="smooth" d="M 144,44 L 199,44 L 199,76 L 144,76 Z" rx="3" fill="url(#subGrad)" stroke="#ea580c" stroke-width="2" />
            
            <path id="if-sub-right" class="smooth" d="M 201,44 L 256,44 L 256,76 L 201,76 Z" rx="3" fill="url(#subGrad)" stroke="#ea580c" stroke-width="2" />
            
            
            <line id="if-bond" class="smooth" x1="200" y1="43" x2="200" y2="77" stroke="#c2410c" stroke-width="2.5" stroke-dasharray="2 2" />

            
            <g id="strain-indicator" class="smooth" opacity="0">
              <circle cx="200" cy="60" r="11" fill="none" stroke="#f59e0b" stroke-width="3" filter="url(#amberGlow)" class="strain-pulse" />
              <path d="M 197,54 L 202,59 L 198,61 L 203,66" stroke="#ffffff" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" />
              <text x="200" y="24" fill="#b45309" font-size="11" font-weight="800" text-anchor="middle" filter="url(#amberGlow)">⚡ Bond Strain</text>
            </g>
            <text id="if-sub-label" class="smooth" x="200" y="38" fill="#9a3412" font-size="11" font-weight="700" text-anchor="middle">Substrate</text>
          </g>
        </svg>
      </div>
    </div>
  </div>

  <script>
    const steps = [
      {
        // Step 0: Initial contact
        lkSubY: -30,
        ifSubY: -30,
        leftLobeShift: 0,
        rightLobeShift: 0,
        arrows: 0,
        strain: 0,
        distortSub: false
      },
      {
        // Step 1: Clamping / Binding
        lkSubY: 4,
        ifSubY: 4,
        leftLobeShift: 14,
        rightLobeShift: -14,
        arrows: 1,
        strain: 0,
        distortSub: false
      },
      {
        // Step 2: Transition State / Bond strain
        lkSubY: 4,
        ifSubY: 4,
        leftLobeShift: 17,
        rightLobeShift: -17,
        arrows: 0,
        strain: 1,
        distortSub: true
      }
    ];

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

    // Elements
    const lkSub = document.getElementById('lk-substrate');
    const ifSub = document.getElementById('if-substrate');
    const ifLeftLobe = document.getElementById('if-left-lobe');
    const ifRightLobe = document.getElementById('if-right-lobe');
    const clampArrows = document.getElementById('clamp-arrows');
    const strainIndicator = document.getElementById('strain-indicator');
    const subLabel = document.getElementById('if-sub-label');
    const ifSubLeft = document.getElementById('if-sub-left');
    const ifSubRight = document.getElementById('if-sub-right');
    const playBtn = document.getElementById('playToggle');
    const stepButtons = document.querySelectorAll('.step-btn');

    function applyStep(index) {
      currentStep = index;
      const s = steps[index];

      // Update buttons
      stepButtons.forEach((btn, idx) => {
        btn.classList.toggle('active', idx === index);
      });

      // Lock and Key
      lkSub.style.transform = `translate(0px, ${s.lkSubY}px)`;

      // Induced Fit Substrate
      ifSub.style.transform = `translate(0px, ${s.ifSubY}px)`;

      // Induced Fit Lobes (Clamping inward)
      ifLeftLobe.style.transform = `translate(${s.leftLobeShift}px, 0px)`;
      ifRightLobe.style.transform = `translate(${s.rightLobeShift}px, 0px)`;

      // Clamping arrows
      clampArrows.style.opacity = s.arrows;

      // Bond Strain / Transition State
      strainIndicator.style.opacity = s.strain;
      subLabel.style.opacity = s.strain ? 0 : 1;

      if (s.distortSub) {
        // Bend substrate slightly under strain
        ifSubLeft.setAttribute('transform', 'rotate(-3 199 76)');
        ifSubRight.setAttribute('transform', 'rotate(3 201 76)');
      } else {
        ifSubLeft.setAttribute('transform', 'rotate(0 199 76)');
        ifSubRight.setAttribute('transform', 'rotate(0 201 76)');
      }
    }

    function nextStep() {
      const next = (currentStep + 1) % steps.length;
      applyStep(next);
    }

    function startAutoPlay() {
      if (timer) clearInterval(timer);
      timer = setInterval(nextStep, 3200);
      playBtn.textContent = '⏸';
      isPlaying = true;
    }

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

    // Step button clicks
    stepButtons.forEach(btn => {
      btn.addEventListener('click', () => {
        const stepIdx = parseInt(btn.getAttribute('data-step'), 10);
        applyStep(stepIdx);
        stopAutoPlay();
      });
    });

    // Play/Pause button
    playBtn.addEventListener('click', () => {
      if (isPlaying) {
        stopAutoPlay();
      } else {
        nextStep();
        startAutoPlay();
      }
    });

    // Initialize
    applyStep(0);
    startAutoPlay();
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Enzyme and Active Site Model</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    
    :root {
      --primary: #22b7ff;
      --primary-dark: #0098e6;
      --text: #1e2945;
      --muted: #64748b;
      --bg: #f8f9fa;
      --card-bg: #ffffff;
      --border: #e6e6e6;
      --enzyme: #e0f2fe;
      --enzyme-stroke: #0284c7;
      --sub-a: #fbbf24;
      --sub-a-stroke: #d97706;
      --sub-b: #38bdf8;
      --sub-b-stroke: #0284c7;
    }

    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: var(--bg);
      color: var(--text);
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 10px 12px;
      gap: 10px;
      user-select: none;
      -webkit-user-select: none;
      overflow-x: hidden;
    }

    /* Top Controls Bar */
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      width: 100%;
      max-width: 480px;
    }

    .step-btn {
      flex: 1;
      padding: 8px 6px;
      font-size: 13px;
      font-weight: 600;
      color: var(--muted);
      background: var(--card-bg);
      border: 1px solid var(--border);
      border-radius: 8px;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      transition: background 0.2s ease, color 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
      box-shadow: 0 1px 2px rgba(0,0,0,0.04);
    }

    .step-btn.active {
      color: #ffffff;
      background: var(--primary-dark);
      border-color: var(--primary-dark);
      box-shadow: 0 2px 6px rgba(0, 152, 230, 0.35);
    }

    .play-btn {
      width: 36px;
      height: 36px;
      flex-shrink: 0;
      padding: 0;
      border-radius: 8px;
      background: var(--card-bg);
      border: 1px solid var(--border);
      color: var(--text);
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 14px;
      transition: background 0.2s ease, border-color 0.2s ease;
      box-shadow: 0 1px 2px rgba(0,0,0,0.04);
    }

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

    /* Diagram Stage Area (Frameless) */
    .stage-card {
      width: 100%;
      max-width: 500px;
      display: flex;
      flex-direction: column;
      align-items: center;
      position: relative;
    }

    .svg-container {
      width: 100%;
      height: auto;
      aspect-ratio: 500 / 290;
      display: block;
    }

    /* Animated Substrate Groups */
    #substrateGroup {
      transition: transform 0.65s cubic-bezier(0.34, 1.2, 0.64, 1);
      transform-origin: 250px 105px;
    }

    #productA {
      transition: transform 0.65s cubic-bezier(0.34, 1.2, 0.64, 1);
      transform-origin: 220px 120px;
    }

    #productB {
      transition: transform 0.65s cubic-bezier(0.34, 1.2, 0.64, 1);
      transform-origin: 280px 120px;
    }

    /* Step States */
    .state-1 #substrateGroup {
      transform: translate(0px, -45px);
    }
    .state-1 #productA {
      transform: translate(0px, 0px);
    }
    .state-1 #productB {
      transform: translate(0px, 0px);
    }

    .state-2 #substrateGroup {
      transform: translate(0px, 32px);
    }
    .state-2 #productA {
      transform: translate(0px, 0px);
    }
    .state-2 #productB {
      transform: translate(0px, 0px);
    }

    .state-3 #substrateGroup {
      transform: translate(0px, 0px);
    }
    .state-3 #productA {
      transform: translate(-45px, -50px) rotate(-14deg);
    }
    .state-3 #productB {
      transform: translate(45px, -50px) rotate(14deg);
    }

    /* Labels & Annotations */
    .diagram-label {
      font-size: 13px;
      font-weight: 700;
      fill: var(--text);
    }

    .tag-bubble {
      opacity: 0;
      transition: opacity 0.35s ease;
      pointer-events: none;
    }

    .state-1 .tag-step1,
    .state-2 .tag-step2,
    .state-3 .tag-step3 {
      opacity: 1;
    }

    .dashed-arrow {
      stroke: var(--primary-dark);
      stroke-width: 2;
      stroke-dasharray: 4, 4;
      fill: none;
    }

    @media (max-width: 380px) {
      .step-btn {
        font-size: 11px;
        padding: 7px 4px;
      }
      .play-btn {
        width: 32px;
        height: 32px;
      }
    }
  </style>
</head>
<body class="state-1">

  
  <div class="controls">
    <button class="step-btn active" id="btn1" onclick="setStep(1)">1. Binding</button>
    <button class="step-btn" id="btn2" onclick="setStep(2)">2. Complex</button>
    <button class="step-btn" id="btn3" onclick="setStep(3)">3. Release</button>
    <button class="play-btn" id="playBtn" onclick="togglePlay()" title="Toggle auto-play">⏸</button>
  </div>

  
  <div class="stage-card">
    <svg class="svg-container" viewBox="0 0 500 290">
      <defs>
        
        <linearGradient id="enzymeGrad" x1="0" y1="0" x2="0" y2="1">
          <stop offset="0%" stop-color="#f0f9ff" />
          <stop offset="100%" stop-color="#bae6fd" />
        </linearGradient>
        <linearGradient id="subAGrad" x1="0" y1="0" x2="1" y2="1">
          <stop offset="0%" stop-color="#fde68a" />
          <stop offset="100%" stop-color="#f59e0b" />
        </linearGradient>
        <linearGradient id="subBGrad" x1="0" y1="0" x2="1" y2="1">
          <stop offset="0%" stop-color="#7dd3fc" />
          <stop offset="100%" stop-color="#0284c7" />
        </linearGradient>
        
        
        <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 L 8 5 L 0 9 z" fill="#0284c7" />
        </marker>
      </defs>

      
      <g class="tag-bubble tag-step1">
        <path class="dashed-arrow" d="M 250 82 L 250 120" marker-end="url(#arrow)"/>
      </g>

      
      <g id="substrateGroup">
        
        <g id="productA">
          <path d="M 215 105 
                   C 195 105, 185 115, 185 130 
                   C 185 145, 195 152, 215 152 
                   L 246 152 
                   C 248 135, 248 122, 246 105 Z" 
                fill="url(#subAGrad)" stroke="var(--sub-a-stroke)" stroke-width="2.5" stroke-linejoin="round"/>
        </g>

        
        <g id="productB">
          <path d="M 254 105 
                   C 252 122, 252 135, 254 152 
                   L 285 152 
                   C 305 152, 315 145, 315 130 
                   C 315 115, 305 105, 285 105 Z" 
                fill="url(#subBGrad)" stroke="var(--sub-b-stroke)" stroke-width="2.5" stroke-linejoin="round"/>
        </g>
      </g>

      
      <path d="M 90 200 
               C 90 145, 140 145, 175 145
               C 180 145, 182 155, 182 165
               C 182 188, 198 190, 244 190
               C 248 190, 250 178, 250 175
               C 250 178, 252 190, 256 190
               C 302 190, 318 188, 318 165
               C 318 155, 320 145, 325 145
               C 360 145, 410 145, 410 200
               C 410 270, 360 280, 250 280
               C 140 280, 90 270, 90 200 Z" 
            fill="url(#enzymeGrad)" 
            stroke="var(--enzyme-stroke)" 
            stroke-width="3" 
            stroke-linejoin="round" />

      
      <g class="tag-bubble tag-step1">
        <rect x="202" y="24" width="96" height="26" rx="6" fill="#ffffff" stroke="var(--border)" stroke-width="1.5"/>
        <text x="250" y="42" text-anchor="middle" class="diagram-label">Substrate</text>

        <rect x="195" y="202" width="110" height="26" rx="6" fill="#ffffff" stroke="var(--primary)" stroke-width="1.5"/>
        <text x="250" y="220" text-anchor="middle" class="diagram-label" fill="#0284c7">Active Site</text>

        <text x="250" y="260" text-anchor="middle" class="diagram-label" fill="var(--muted)">Enzyme</text>
      </g>

      
      <g class="tag-bubble tag-step2">
        <rect x="135" y="30" width="230" height="30" rx="8" fill="#ffffff" stroke="var(--primary)" stroke-width="2"/>
        <text x="250" y="51" text-anchor="middle" class="diagram-label" fill="#0284c7">Enzyme-Substrate Complex</text>
        
        <text x="250" y="260" text-anchor="middle" class="diagram-label" fill="var(--muted)">Enzyme</text>
      </g>

      
      <g class="tag-bubble tag-step3">
        <rect x="205" y="20" width="90" height="26" rx="6" fill="#ffffff" stroke="var(--border)" stroke-width="1.5"/>
        <text x="250" y="38" text-anchor="middle" class="diagram-label">Products</text>

        <rect x="170" y="244" width="160" height="26" rx="6" fill="#ffffff" stroke="var(--border)" stroke-width="1.5"/>
        <text x="250" y="262" text-anchor="middle" class="diagram-label" fill="var(--muted)">Unchanged Enzyme</text>
      </g>
    </svg>
  </div>

  <script>
    let currentStep = 1;
    let isPlaying = true;
    let timer = null;

    function setStep(step) {
      currentStep = step;
      document.body.className = 'state-' + step;
      
      for (let i = 1; i <= 3; i++) {
        const btn = document.getElementById('btn' + i);
        if (btn) {
          btn.classList.toggle('active', i === step);
        }
      }
    }

    function nextStep() {
      const next = currentStep >= 3 ? 1 : currentStep + 1;
      setStep(next);
    }

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

    function startTimer() {
      clearInterval(timer);
      timer = setInterval(() => {
        if (isPlaying) {
          nextStep();
        }
      }, 3200);
    }

    startTimer();
  </script>
</body>
</html>

112.43(b)(11)(B)

Aligned learning resources

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