<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      width: 100%;
      background: #ffffff;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e293b;
      user-select: none;
      padding: 8px;
    }
    .diagram-container {
      display: flex;
      flex-direction: column;
      gap: 10px;
      max-width: 580px;
      margin: 0 auto;
    }
    .section-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      flex-wrap: wrap;
      gap: 6px;
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    .section-title {
      font-size: 13px;
      font-weight: 800;
      color: #0f172a;
      letter-spacing: -0.2px;
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    .controls {
      display: flex;
      gap: 4px;
      align-items: center;
      flex-wrap: wrap;
    }
    .btn-step {
      background: #f8fafc;
      border: 1px solid #94a3b8;
      border-radius: 4px;
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      font-size: 11px;
      font-weight: 700;
      cursor: pointer;
      color: #334155;
      transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease;
    }
    .btn-step.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }
    .stage-svg {
      width: 100%;
      height: auto;
      display: block;
    }
    .legend-item {
      display: inline-flex;
      align-items: center;
      font-size: 11px;
      font-weight: 700;
      padding: 2px 7px;
      border-radius: 4px;
      cursor: pointer;
      border: 1px solid transparent;
      transition: opacity 0.2s ease, border-color 0.2s ease;
    }
    .legend-d { color: #b91c1c; background: #fee2e2; border-color: #fca5a5; }
    .legend-e { color: #b45309; background: #fef3c7; border-color: #fcd34d; }
    .legend-a { color: #15803d; background: #dcfce7; border-color: #86efac; }
    .legend-b { color: #1d4ed8; background: #dbeafe; border-color: #93c5fd; }
    .dimmed { opacity: 0.18; }
    .highlight { stroke-width: 3.5px !important; }
  </style>
</head>
<body>

<div class="diagram-container">
  
  <div class="panel-block">
    <div class="section-header">
      <span class="section-title">1. CDK Activation Mechanism</span>
      <div class="controls">
        <button class="btn-step active" id="btn1" onclick="setStep(0)">1. Inactive</button>
        <button class="btn-step" id="btn2" onclick="setStep(1)">2. +Cyclin</button>
        <button class="btn-step" id="btn3" onclick="setStep(2)">3. +Phosphate</button>
        <button class="btn-step" id="btn4" onclick="setStep(3)">4. Active (ON)</button>
      </div>
    </div>

    <svg class="stage-svg" viewBox="0 0 420 108" id="cdkSvg">
      
      <text id="statusDesc" x="210" y="13" text-anchor="middle" font-size="11" font-weight="600" fill="#475569">Inactive catalytic subunit alone (active site blocked)</text>

      
      <g id="targetGroup" transform="translate(305, 34)" style="transition: all 0.35s ease;">
        <rect id="targetRect" x="0" y="6" width="95" height="38" rx="6" fill="#f1f5f9" stroke="#475569" stroke-width="1.8"/>
        <text id="targetText" x="42" y="30" text-anchor="middle" font-size="12" font-weight="800" fill="#1e293b">Target OFF</text>
        
        <g id="targetPBadge" opacity="0" transform="translate(86, 25)" style="transition: opacity 0.35s ease;">
          <circle cx="0" cy="0" r="9" fill="#eab308" stroke="#a16207" stroke-width="1.5"/>
          <text x="0" y="3.5" text-anchor="middle" font-size="10" font-weight="800" fill="#713f12">P</text>
        </g>
      </g>

      
      <g id="transferArrow" opacity="0" style="transition: opacity 0.35s ease;">
        <path d="M 268,48 C 285,42 295,44 304,48" fill="none" stroke="#ca8a04" stroke-width="2" stroke-dasharray="3,2"/>
        <polygon points="306,48 299,44 300,51" fill="#ca8a04"/>
      </g>

      
      <g id="atpGroup" transform="translate(222, 38)" opacity="0" style="transition: all 0.35s ease;">
        <rect id="atpRect" x="0" y="4" width="42" height="22" rx="4" fill="#ffedd5" stroke="#ea580c" stroke-width="1.5"/>
        <text id="atpText" x="21" y="19" text-anchor="middle" font-size="11" font-weight="800" fill="#9a3412">ATP</text>
      </g>

      
      <g id="cdkGroup" transform="translate(112, 60)" style="transition: transform 0.35s ease;">
        
        <path id="cdkBase" d="M -30,0 A 30,30 0 1,0 0,-30 L 0,-13 A 13,13 0 0,1 -13,0 Z" fill="#64748b" stroke="#334155" stroke-width="2"/>
        
        <text x="-12" y="14" text-anchor="middle" font-size="11" font-weight="800" fill="#ffffff" letter-spacing="0.5px">CDK</text>
      </g>

      
      <g id="cyclinGroup" transform="translate(24, 25)" style="transition: transform 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);">
        <path d="M 0,0 L 22,0 A 13,13 0 0,0 35,13 L 35,33 L 0,33 Z" fill="#16a34a" stroke="#14532d" stroke-width="1.8"/>
        <text x="16" y="20" text-anchor="middle" font-size="10" font-weight="800" fill="#ffffff">Cyclin</text>
      </g>

      
      <g id="cakPGroup" transform="translate(138, 20)" opacity="0" style="transition: opacity 0.35s ease, transform 0.35s ease;">
        <polygon points="10,0 13,7 20,7 15,12 17,19 10,14 3,19 5,12 0,7 7,7" fill="#eab308" stroke="#a16207" stroke-width="1.2"/>
        <text x="10" y="12.5" text-anchor="middle" font-size="8.5" font-weight="900" fill="#713f12">P</text>
      </g>

      
      <g id="activeCleft" transform="translate(152, 54)" opacity="0" style="transition: opacity 0.35s ease;">
        <circle cx="0" cy="0" r="6.5" fill="#38bdf8" stroke="#0284c7" stroke-width="1.2"/>
        <text x="0" y="3" text-anchor="middle" font-size="9" font-weight="900" fill="#0369a1">✦</text>
      </g>
    </svg>
  </div>

  
  <div class="panel-block">
    <div class="section-header">
      <span class="section-title">2. Cyclin Waves Across Cell Cycle</span>
      <div class="controls">
        <span class="legend-item legend-d" onclick="filterWave('D')">D (G₁)</span>
        <span class="legend-item legend-e" onclick="filterWave('E')">E (G₁/S)</span>
        <span class="legend-item legend-a" onclick="filterWave('A')">A (S/G₂)</span>
        <span class="legend-item legend-b" onclick="filterWave('B')">B (M)</span>
      </div>
    </div>

    <svg class="stage-svg" viewBox="0 0 420 112" id="waveSvg">
      
      <rect x="35" y="6" width="115" height="84" fill="#f8fafc"/>
      <rect x="150" y="6" width="105" height="84" fill="#f1f5f9"/>
      <rect x="255" y="6" width="85" height="84" fill="#f8fafc"/>
      <rect x="340" y="6" width="70" height="84" fill="#f1f5f9"/>

      
      <line x1="150" y1="6" x2="150" y2="90" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>
      <line x1="255" y1="6" x2="255" y2="90" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>
      <line x1="340" y1="6" x2="340" y2="90" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3,3"/>

      
      <text x="92" y="19" text-anchor="middle" font-size="11" font-weight="800" fill="#475569">G₁ Phase</text>
      <text x="202" y="19" text-anchor="middle" font-size="11" font-weight="800" fill="#475569">S Phase</text>
      <text x="297" y="19" text-anchor="middle" font-size="11" font-weight="800" fill="#475569">G₂ Phase</text>
      <text x="375" y="19" text-anchor="middle" font-size="11" font-weight="800" fill="#475569">M</text>

      
      <line x1="35" y1="90" x2="410" y2="90" stroke="#64748b" stroke-width="1.5"/>
      <line x1="35" y1="6" x2="35" y2="90" stroke="#64748b" stroke-width="1.5"/>
      
      
      <text x="14" y="52" text-anchor="middle" font-size="9" font-weight="700" fill="#64748b" transform="rotate(-90 14 52)">Level</text>
      <text x="408" y="102" text-anchor="end" font-size="9.5" font-weight="700" fill="#64748b">Time →</text>

      
      <path id="waveD" d="M 35,90 Q 55,38 95,38 Q 130,38 160,78 L 410,88" fill="none" stroke="#dc2626" stroke-width="2.5" stroke-linecap="round"/>

      
      <path id="waveE" d="M 35,90 L 85,88 Q 140,26 150,26 Q 165,26 200,88 L 410,90" fill="none" stroke="#d97706" stroke-width="2.5" stroke-linecap="round"/>

      
      <path id="waveA" d="M 35,90 L 150,90 Q 220,80 285,28 Q 320,28 345,82 L 360,90 L 410,90" fill="none" stroke="#16a34a" stroke-width="2.5" stroke-linecap="round"/>

      
      <path id="waveB" d="M 35,90 L 255,90 Q 315,75 358,24 L 372,30 L 382,90 L 410,90" fill="none" stroke="#2563eb" stroke-width="2.5" stroke-linecap="round"/>

      
      <g transform="translate(382, 45)">
        <text x="0" y="0" font-size="11" fill="#dc2626" text-anchor="middle">⚡</text>
        <text x="0" y="10" font-size="8.5" font-weight="800" fill="#b91c1c" text-anchor="middle">Ub</text>
      </g>
    </svg>
  </div>
</div>

<script>
  let curStep = 0;
  let activeFilter = null;

  const stepDescriptions = [
    "1. Inactive CDK alone (T-loop blocks active catalytic site)",
    "2. Cyclin binds CDK, causing partial conformational change",
    "3. CAK kinase adds activating Phosphate (P), fully exposing active site",
    "4. Active CDK-Cyclin transfers phosphate from ATP to target protein (ON)"
  ];

  function setStep(s) {
    curStep = s;
    for (let i = 0; i < 4; i++) {
      document.getElementById('btn' + (i + 1)).classList.toggle('active', i === s);
    }

    const desc = document.getElementById('statusDesc');
    const cyclin = document.getElementById('cyclinGroup');
    const cak = document.getElementById('cakPGroup');
    const cleft = document.getElementById('activeCleft');
    const atp = document.getElementById('atpGroup');
    const atpText = document.getElementById('atpText');
    const atpRect = document.getElementById('atpRect');
    const targetRect = document.getElementById('targetRect');
    const targetText = document.getElementById('targetText');
    const targetPBadge = document.getElementById('targetPBadge');
    const arrow = document.getElementById('transferArrow');

    desc.textContent = stepDescriptions[s];

    if (s === 0) {
      cyclin.setAttribute('transform', 'translate(24, 25)');
      cak.setAttribute('opacity', '0');
      cleft.setAttribute('opacity', '0');
      atp.setAttribute('opacity', '0');
      arrow.setAttribute('opacity', '0');
      
      targetRect.setAttribute('fill', '#f1f5f9');
      targetRect.setAttribute('stroke', '#475569');
      targetText.setAttribute('fill', '#1e293b');
      targetText.textContent = 'Target OFF';
      targetPBadge.setAttribute('opacity', '0');
    } else if (s === 1) {
      // Cyclin docked precisely into CDK cleft
      cyclin.setAttribute('transform', 'translate(99, 27)');
      cak.setAttribute('opacity', '0');
      cleft.setAttribute('opacity', '0');
      atp.setAttribute('opacity', '0');
      arrow.setAttribute('opacity', '0');

      targetRect.setAttribute('fill', '#f1f5f9');
      targetRect.setAttribute('stroke', '#475569');
      targetText.setAttribute('fill', '#1e293b');
      targetText.textContent = 'Target OFF';
      targetPBadge.setAttribute('opacity', '0');
    } else if (s === 2) {
      // Activating phosphate added & ATP loaded
      cyclin.setAttribute('transform', 'translate(99, 27)');
      cak.setAttribute('opacity', '1');
      cleft.setAttribute('opacity', '1');
      atp.setAttribute('opacity', '1');
      atpText.textContent = 'ATP';
      atpRect.setAttribute('fill', '#ffedd5');
      atpRect.setAttribute('stroke', '#ea580c');
      arrow.setAttribute('opacity', '0');

      targetRect.setAttribute('fill', '#f1f5f9');
      targetRect.setAttribute('stroke', '#475569');
      targetText.setAttribute('fill', '#1e293b');
      targetText.textContent = 'Target OFF';
      targetPBadge.setAttribute('opacity', '0');
    } else if (s === 3) {
      // Fully active kinase transferring phosphate
      cyclin.setAttribute('transform', 'translate(99, 27)');
      cak.setAttribute('opacity', '1');
      cleft.setAttribute('opacity', '1');
      atp.setAttribute('opacity', '1');
      atpText.textContent = 'ADP';
      atpRect.setAttribute('fill', '#e2e8f0');
      atpRect.setAttribute('stroke', '#64748b');
      arrow.setAttribute('opacity', '1');

      targetRect.setAttribute('fill', '#dcfce7');
      targetRect.setAttribute('stroke', '#16a34a');
      targetText.setAttribute('fill', '#14532d');
      targetText.textContent = 'Target ON';
      targetPBadge.setAttribute('opacity', '1');
    }
  }

  function filterWave(type) {
    const waves = ['D', 'E', 'A', 'B'];
    if (activeFilter === type) {
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      waves.forEach(w => {
        const el = document.getElementById('wave' + w);
        el.classList.remove('dimmed', 'highlight');
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        if (w === type) {
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        } else {
          el.classList.add('dimmed');
          el.classList.remove('highlight');
        }
      });
    }
  }

  // Auto-advance step calmly
  let timer = setInterval(() => {
    setStep((curStep + 1) % 4);
  }, 4000);

  // Pause on user interaction
  document.querySelectorAll('.btn-step, .legend-item').forEach(btn => {
    btn.addEventListener('click', () => clearInterval(timer));
  });
</script>
</body>
</html>

Eukaryotic Cell Cycle Phases and Checkpoint Regulation

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>G1 Checkpoint Regulation</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      width: 100%;
      min-height: 100%;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: transparent;
      color: #1e293b;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 10px 8px;
    }

    /* Pathway Selector Buttons */
    .controls {
      display: flex;
      gap: 10px;
      margin-bottom: 12px;
      width: 100%;
      max-width: 440px;
    }
    .toggle-btn {
      flex: 1;
      padding: 9px 12px;
      font-size: 13px;
      font-weight: 700;
      border: 1.5px solid #cbd5e1;
      border-radius: 8px;
      background: #ffffff;
      color: #475569;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: background 0.3s ease, border-color 0.3s ease, color 0.3s ease, box-shadow 0.3s ease;
      -webkit-tap-highlight-color: transparent;
    }
    .toggle-btn:hover {
      background: #f8fafc;
    }
    .toggle-btn.active-a {
      background: #ecfdf5;
      border-color: #10b981;
      color: #065f46;
      box-shadow: 0 0 0 1.5px #10b981;
    }
    .toggle-btn.active-b {
      background: #fef2f2;
      border-color: #ef4444;
      color: #991b1b;
      box-shadow: 0 0 0 1.5px #ef4444;
    }

    /* Diagram Canvas */
    .stage {
      width: 100%;
      max-width: 440px;
      margin: 0 auto;
    }

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

    /* Molecular Node Styling & Transitions */
    .node, .cascade-item, .path-line, .status-group {
      transition: opacity 0.45s ease, transform 0.45s ease, fill 0.45s ease, stroke 0.45s ease;
    }
    
    text {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      user-select: none;
    }

    .flow-line {
      stroke-dasharray: 6 4;
      animation: smoothDash 3s linear infinite;
    }
    @keyframes smoothDash {
      to { stroke-dashoffset: -20; }
    }

    /* Mobile adjustments */
    @media (max-width: 380px) {
      .toggle-btn {
        font-size: 12px;
        padding: 8px 6px;
        gap: 4px;
      }
    }
  </style>
</head>
<body>

  <div class="controls">
    <button id="btnA" class="toggle-btn active-a" onclick="setMode('A')" aria-pressed="true">
      <span>✦</span> Path A: Normal (Growth)
    </button>
    <button id="btnB" class="toggle-btn" onclick="setMode('B')" aria-pressed="false">
      <span>⚡</span> Path B: DNA Damage
    </button>
  </div>

  <div class="stage">
    <svg viewBox="0 0 420 380" aria-label="G1 Checkpoint Regulation Diagram">
      <defs>
        
        <marker id="arrow-green" markerWidth="7" markerHeight="7" refX="6" refY="3.5" orient="auto">
          <polygon points="0 0, 7 3.5, 0 7" fill="#10b981" />
        </marker>
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          <polygon points="0 0, 7 3.5, 0 7" fill="#ef4444" />
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        </marker>
        
        <marker id="bar-red" markerWidth="8" markerHeight="8" refX="4" refY="4" orient="auto">
          <line x1="4" y1="0.5" x2="4" y2="7.5" stroke="#ef4444" stroke-width="3" stroke-linecap="round" />
        </marker>
      </defs>

      
      
      
      <g id="mitogenGroup" class="node" transform="translate(65, 42)">
        <rect x="-55" y="-22" width="110" height="44" rx="10" fill="#ecfdf5" stroke="#10b981" stroke-width="2"/>
        <text y="-2" text-anchor="middle" font-size="13" font-weight="700" fill="#047857">Mitogen</text>
        <text y="14" text-anchor="middle" font-size="11" font-weight="600" fill="#059669">(Growth Factor)</text>
      </g>

      
      <line id="lineA1" class="flow-line path-line" x1="120" y1="42" x2="218" y2="42" stroke="#10b981" stroke-width="2.5" marker-end="url(#arrow-green)" />

      
      <g id="damageGroup" class="node" transform="translate(65, 42)" style="opacity: 0; pointer-events: none;">
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        <text y="-2" text-anchor="middle" font-size="12.5" font-weight="700" fill="#b91c1c">Double-Strand</text>
        <text y="14" text-anchor="middle" font-size="12" font-weight="700" fill="#dc2626">DNA Break</text>
      </g>

      
      <g id="damageCascade" style="opacity: 0; pointer-events: none; transition: opacity 0.45s ease;">
        
        <line x1="65" y1="64" x2="65" y2="92" stroke="#ef4444" stroke-width="2" marker-end="url(#arrow-red)" />
        
        
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        <text x="65" y="183" text-anchor="middle" font-size="9.5" font-weight="600" fill="#b91c1c">Phosphorylated</text>

        
        <line x1="65" y1="188" x2="65" y2="212" stroke="#ef4444" stroke-width="2" marker-end="url(#arrow-red)" />
        
        
        <rect x="15" y="214" width="100" height="36" rx="8" fill="#ef4444" stroke="#b91c1c" stroke-width="2"/>
        <text x="65" y="232" text-anchor="middle" font-size="13" font-weight="800" fill="#ffffff">p21 Protein</text>
        <text x="65" y="244" text-anchor="middle" font-size="10" font-weight="600" fill="#fee2e2">CDK Inhibitor</text>

        
        <path d="M 115 232 L 305 232 L 305 73" fill="none" stroke="#ef4444" stroke-width="2.5" stroke-dasharray="4 3" marker-end="url(#bar-red)" />
      </g>

      

      
      <g id="cdkComplex" class="node" transform="translate(305, 42)">
        <rect id="cdkBg" x="-80" y="-24" width="160" height="48" rx="10" fill="#eff6ff" stroke="#3b82f6" stroke-width="2.2"/>
        <text id="cdkText" y="-3" text-anchor="middle" font-size="13" font-weight="700" fill="#1d4ed8">Cyclin D • CDK4/6</text>
        <text id="cdkSub" y="14" text-anchor="middle" font-size="11.5" font-weight="700" fill="#2563eb">ACTIVE (Kinase ON)</text>
      </g>

      
      <line id="cdkToRb" class="flow-line path-line" x1="305" y1="66" x2="305" y2="128" stroke="#2563eb" stroke-width="2.5" marker-end="url(#arrow-blue)" />

      
      <text id="phosLabel" x="312" y="100" font-size="11" font-weight="700" fill="#2563eb" text-anchor="start" style="transition: opacity 0.45s ease;">+ Phosphate (P)</text>

      
      <g id="switchRegion" transform="translate(305, 172)">
        
        
        <g id="statusBadge" class="status-group" transform="translate(0, -32)">
          <rect id="statusBg" x="-85" y="-12" width="170" height="24" rx="12" fill="#ecfdf5" stroke="#10b981" stroke-width="1.5"/>
          <text id="bindStatus" y="4.5" text-anchor="middle" font-size="12" font-weight="700" fill="#047857">🔓 Rb releases E2F</text>
        </g>

        
        <line id="rbE2fLink" x1="-38" y1="6" x2="38" y2="6" stroke="#cbd5e1" stroke-width="2" stroke-dasharray="3 3" style="transition: all 0.45s ease;" />

        
        <g id="rbNode" class="node" transform="translate(-54, 6)">
          <rect x="-28" y="-18" width="56" height="36" rx="8" fill="#f8fafc" stroke="#475569" stroke-width="2"/>
          <text y="5" text-anchor="middle" font-size="13" font-weight="800" fill="#1e293b">Rb</text>
          
          <g id="pTag" style="transition: opacity 0.45s ease, transform 0.45s ease; opacity: 1;">
            <circle cx="22" cy="-14" r="9.5" fill="#f59e0b" stroke="#b45309" stroke-width="1.5"/>
            <text x="22" y="-10" text-anchor="middle" font-size="10" font-weight="900" fill="#ffffff">P</text>
          </g>
        </g>

        
        <g id="e2fNode" class="node" transform="translate(54, 6)">
          <polygon points="0,-20 34,0 0,20 -34,0" fill="#dbeafe" stroke="#2563eb" stroke-width="2"/>
          <text y="4.5" text-anchor="middle" font-size="12.5" font-weight="800" fill="#1d4ed8">E2F</text>
        </g>
      </g>

      
      <line id="e2fToGene" class="flow-line path-line" x1="305" y1="210" x2="305" y2="280" stroke="#10b981" stroke-width="2.5" marker-end="url(#arrow-green)" />

      
      <g id="outcomeGroup" class="node" transform="translate(210, 328)">
        <rect id="outcomeBox" x="-195" y="-24" width="390" height="48" rx="10" fill="#ecfdf5" stroke="#10b981" stroke-width="2"/>
        <text id="outcomeTitle" x="0" y="-3" text-anchor="middle" font-size="13.5" font-weight="800" fill="#065f46">
          S-Phase Genes Active (Polymerases / TK)
        </text>
        <text id="outcomeSub" x="0" y="14" text-anchor="middle" font-size="12" font-weight="700" fill="#047857">
          Cell commits to S Phase (DNA Replication)
        </text>
      </g>

    </svg>
  </div>

  <script>
    function setMode(mode) {
      const btnA = document.getElementById('btnA');
      const btnB = document.getElementById('btnB');
      const mitogen = document.getElementById('mitogenGroup');
      const damage = document.getElementById('damageGroup');
      const damageCascade = document.getElementById('damageCascade');
      const lineA1 = document.getElementById('lineA1');
      const cdkBg = document.getElementById('cdkBg');
      const cdkText = document.getElementById('cdkText');
      const cdkSub = document.getElementById('cdkSub');
      const cdkToRb = document.getElementById('cdkToRb');
      const phosLabel = document.getElementById('phosLabel');
      const pTag = document.getElementById('pTag');
      const rbNode = document.getElementById('rbNode');
      const e2fNode = document.getElementById('e2fNode');
      const rbE2fLink = document.getElementById('rbE2fLink');
      const statusBg = document.getElementById('statusBg');
      const bindStatus = document.getElementById('bindStatus');
      const e2fToGene = document.getElementById('e2fToGene');
      const outcomeBox = document.getElementById('outcomeBox');
      const outcomeTitle = document.getElementById('outcomeTitle');
      const outcomeSub = document.getElementById('outcomeSub');

      if (mode === 'A') {
        // Path A: Normal Mitogenic Growth
        btnA.className = 'toggle-btn active-a';
        btnB.className = 'toggle-btn';
        btnA.setAttribute('aria-pressed', 'true');
        btnB.setAttribute('aria-pressed', 'false');

        mitogen.style.opacity = '1';
        damage.style.opacity = '0';
        damageCascade.style.opacity = '0';
        lineA1.style.opacity = '1';

        // CDK Active
        cdkBg.setAttribute('fill', '#eff6ff');
        cdkBg.setAttribute('stroke', '#3b82f6');
        cdkText.setAttribute('fill', '#1d4ed8');
        cdkSub.textContent = 'ACTIVE (Kinase ON)';
        cdkSub.setAttribute('fill', '#2563eb');

        // CDK phosphorylates Rb
        cdkToRb.setAttribute('stroke', '#2563eb');
        cdkToRb.setAttribute('marker-end', 'url(#arrow-blue)');
        cdkToRb.classList.add('flow-line');
        cdkToRb.style.opacity = '1';
        phosLabel.style.opacity = '1';

        // Rb phosphorylated & separates from E2F
        pTag.style.opacity = '1';
        pTag.style.transform = 'scale(1)';
        rbNode.setAttribute('transform', 'translate(-54, 6)');
        e2fNode.setAttribute('transform', 'translate(54, 6)');
        rbE2fLink.setAttribute('x1', '-26');
        rbE2fLink.setAttribute('x2', '20');
        rbE2fLink.style.opacity = '0.2';
        
        statusBg.setAttribute('fill', '#ecfdf5');
        statusBg.setAttribute('stroke', '#10b981');
        bindStatus.setAttribute('fill', '#047857');
        bindStatus.textContent = '🔓 Rb releases E2F (Active)';

        // E2F triggers transcription
        e2fToGene.style.opacity = '1';
        e2fToGene.setAttribute('stroke', '#10b981');
        e2fToGene.setAttribute('marker-end', 'url(#arrow-green)');
        e2fToGene.classList.add('flow-line');

        outcomeBox.setAttribute('fill', '#ecfdf5');
        outcomeBox.setAttribute('stroke', '#10b981');
        outcomeTitle.setAttribute('fill', '#065f46');
        outcomeTitle.textContent = 'S-Phase Genes Active (Polymerases / TK)';
        outcomeSub.setAttribute('fill', '#047857');
        outcomeSub.textContent = 'Cell commits to S Phase (DNA Replication)';

      } else {
        // Path B: DNA Damage Checkpoint Arrest
        btnB.className = 'toggle-btn active-b';
        btnA.className = 'toggle-btn';
        btnA.setAttribute('aria-pressed', 'false');
        btnB.setAttribute('aria-pressed', 'true');

        mitogen.style.opacity = '0';
        damage.style.opacity = '1';
        damageCascade.style.opacity = '1';
        lineA1.style.opacity = '0';

        // CDK Blocked by p21
        cdkBg.setAttribute('fill', '#f8fafc');
        cdkBg.setAttribute('stroke', '#94a3b8');
        cdkText.setAttribute('fill', '#64748b');
        cdkSub.textContent = 'BLOCKED by p21';
        cdkSub.setAttribute('fill', '#dc2626');

        // No Phosphorylation
        cdkToRb.setAttribute('stroke', '#cbd5e1');
        cdkToRb.setAttribute('marker-end', 'url(#arrow-gray)');
        cdkToRb.classList.remove('flow-line');
        cdkToRb.style.opacity = '0.35';
        phosLabel.style.opacity = '0.2';

        // Rb remains unphosphorylated & tightly binds E2F
        pTag.style.opacity = '0';
        pTag.style.transform = 'scale(0.5)';
        rbNode.setAttribute('transform', 'translate(-26, 6)');
        e2fNode.setAttribute('transform', 'translate(26, 6)');
        rbE2fLink.setAttribute('x1', '0');
        rbE2fLink.setAttribute('x2', '0');
        rbE2fLink.style.opacity = '0.8';

        statusBg.setAttribute('fill', '#fef2f2');
        statusBg.setAttribute('stroke', '#ef4444');
        bindStatus.setAttribute('fill', '#991b1b');
        bindStatus.textContent = '🔒 Rb bound to E2F (Inhibited)';

        // E2F Inactive
        e2fToGene.style.opacity = '0.25';
        e2fToGene.setAttribute('stroke', '#94a3b8');
        e2fToGene.setAttribute('marker-end', 'url(#arrow-gray)');
        e2fToGene.classList.remove('flow-line');

        outcomeBox.setAttribute('fill', '#fef2f2');
        outcomeBox.setAttribute('stroke', '#ef4444');
        outcomeTitle.setAttribute('fill', '#991b1b');
        outcomeTitle.textContent = 'S-Phase Genes Repressed';
        outcomeSub.setAttribute('fill', '#b91c1c');
        outcomeSub.textContent = 'Cell Halts at G1 Checkpoint (DNA Repair / Apoptosis)';
      }
    }

    // Initialize in Path A
    setMode('A');
  </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>Cell Cycle Checkpoints</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: transparent;
      color: #0f172a;
      padding: 6px 8px;
      display: flex;
      flex-direction: column;
      gap: 6px;
      user-select: none;
      max-width: 680px;
      margin: 0 auto;
    }
    
    .nav-bar {
      display: flex;
      justify-content: center;
      gap: 10px;
      padding-bottom: 2px;
    }

    .tab-btn {
      background: #ffffff;
      border: 1.5px solid #cbd5e1;
      color: #475569;
      padding: 5px 14px;
      border-radius: 999px;
      font-size: 12px;
      font-weight: 700;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      transition: background-color 0.2s, border-color 0.2s, color 0.2s;
    }

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

    .tab-btn.active-wait {
      background: #fef2f2;
      border-color: #ef4444;
      color: #b91c1c;
    }

    .tab-btn.active-pass {
      background: #ecfdf5;
      border-color: #10b981;
      color: #047857;
    }

    .checkpoint-section {
      display: flex;
      flex-direction: column;
      gap: 2px;
    }

    .header-row {
      display: flex;
      justify-content: space-between;
      align-items: center;
      padding: 2px 2px 3px 2px;
      border-bottom: 1px solid #e2e8f0;
    }

    .title {
      font-size: 12px;
      font-weight: 700;
      letter-spacing: 0.2px;
      color: #334155;
      display: flex;
      align-items: center;
      gap: 5px;
    }

    .badge {
      font-size: 10px;
      font-weight: 700;
      padding: 2px 7px;
      border-radius: 6px;
      text-transform: uppercase;
      letter-spacing: 0.4px;
    }

    .badge-wait {
      background: #fee2e2;
      color: #991b1b;
    }

    .badge-go {
      background: #dcfce7;
      color: #166534;
    }

    .diagram-svg {
      width: 100%;
      height: auto;
      max-height: 120px;
      display: block;
    }

    text {
      font-family: system-ui, -apple-system, sans-serif;
      font-size: 11px;
      font-weight: 600;
      fill: #0f172a;
    }

    .sub-text {
      font-size: 10px;
      font-weight: 500;
      fill: #64748b;
    }
  </style>
</head>
<body>

  <div class="nav-bar">
    <button id="btnWait" class="tab-btn active-wait" onclick="setState('wait')">
      <span>✋</span> <span>1. Checkpoint Active</span>
    </button>
    <button id="btnPass" class="tab-btn" onclick="setState('pass')">
      <span>▶</span> <span>2. Checkpoint Cleared</span>
    </button>
  </div>

  
  <div class="checkpoint-section">
    <div class="header-row">
      <span class="title">🔬 G₂ / M Checkpoint</span>
      <span id="g2Badge" class="badge badge-wait">DNA Check</span>
    </div>
    
    <svg id="svgG2" class="diagram-svg" viewBox="0 0 450 94">
      <defs>
        <marker id="arrow" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="5" markerHeight="5" orient="auto-start-reverse">
          <path d="M 0 1 L 10 5 L 0 9 z" fill="#94a3b8" />
        </marker>
        <marker id="arrow-green" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="5" markerHeight="5" orient="auto-start-reverse">
          <path d="M 0 1 L 10 5 L 0 9 z" fill="#10b981" />
        </marker>
        <filter id="subtle-shadow" x="-5%" y="-5%" width="110%" height="110%">
          <feDropShadow dx="0" dy="1" stdDeviation="1" flood-opacity="0.06"/>
        </filter>
      </defs>

      
      <g id="g2Regulator" transform="translate(52, 42)">
        <rect id="regBox" x="-46" y="-23" width="92" height="46" rx="6" fill="#fef2f2" stroke="#f87171" stroke-width="1.5" filter="url(#subtle-shadow)"/>
        <text id="regTitle" x="0" y="-3" text-anchor="middle" font-size="12" font-weight="700" fill="#dc2626">Wee1</text>
        <text id="regAction" x="0" y="13" text-anchor="middle" font-size="10.5" font-weight="600" fill="#991b1b">+ Inhibitory Ⓟ</text>
      </g>

      
      <path id="g2Arrow1" d="M 104 42 L 152 42" stroke="#f87171" stroke-width="2" stroke-dasharray="4,3" marker-end="url(#arrow)"/>

      
      <g id="g2Complex" transform="translate(225, 42)">
        
        <circle cx="-23" cy="-2" r="25" fill="#e0e7ff" stroke="#6366f1" stroke-width="1.8"/>
        <text x="-23" y="2" text-anchor="middle" font-size="10" font-weight="700" fill="#3730a3">Cyclin B</text>
        
        <circle cx="23" cy="-2" r="25" fill="#cffafe" stroke="#06b6d4" stroke-width="1.8"/>
        <text x="23" y="2" text-anchor="middle" font-size="10" font-weight="700" fill="#155e75">CDK1</text>
        
        
        <g id="phosphateGroup" transform="translate(23, -29)">
          <circle cx="0" cy="0" r="11" fill="#ef4444" stroke="#ffffff" stroke-width="1.5"/>
          <text x="0" y="4" text-anchor="middle" fill="#ffffff" font-size="11" font-weight="800">Ⓟ</text>
        </g>
        
        <text id="mpfStatus" x="0" y="37" text-anchor="middle" font-size="11" font-weight="700" fill="#dc2626">Inactive MPF</text>
      </g>

      
      <path id="g2Arrow2" d="M 292 42 L 334 42" stroke="#cbd5e1" stroke-width="2" marker-end="url(#arrow)"/>

      
      <g id="g2Outcome" transform="translate(390, 42)">
        <rect id="outBox" x="-52" y="-26" width="104" height="52" rx="6" fill="#f8fafc" stroke="#cbd5e1" stroke-width="1.5" filter="url(#subtle-shadow)"/>
        <text id="outIcon" x="0" y="-8" text-anchor="middle" font-size="13">⏸</text>
        <text id="outText1" x="0" y="8" text-anchor="middle" font-size="11" font-weight="700" fill="#64748b">G₂ Arrest</text>
        <text id="outText2" x="0" y="20" text-anchor="middle" font-size="9.5" fill="#94a3b8">Repairing DNA</text>
      </g>
    </svg>
  </div>

  
  <div class="checkpoint-section">
    <div class="header-row">
      <span class="title">⚡ Spindle Assembly Checkpoint (SAC)</span>
      <span id="sacBadge" class="badge badge-wait">Alignment Check</span>
    </div>

    <svg id="svgSAC" class="diagram-svg" viewBox="0 0 450 94">
      
      <g id="sacKineto" transform="translate(52, 42)">
        <rect id="kinBox" x="-46" y="-25" width="92" height="50" rx="6" fill="#fef2f2" stroke="#f87171" stroke-width="1.5" filter="url(#subtle-shadow)"/>
        <text id="kinIcon" x="0" y="-8" text-anchor="middle" font-size="13">⚠️</text>
        <text id="kinText1" x="0" y="7" text-anchor="middle" font-size="11" font-weight="700" fill="#dc2626">Unattached</text>
        <text id="kinText2" x="0" y="19" text-anchor="middle" font-size="10" font-weight="600" fill="#991b1b">Mad2 Signal</text>
      </g>

      
      <path id="sacArrow1" d="M 104 42 L 146 42" stroke="#ef4444" stroke-width="2" marker-end="url(#arrow)"/>
      <text id="sacInhibitLabel" x="125" y="34" text-anchor="middle" font-size="12" fill="#ef4444">⛔</text>

      
      <g id="sacAPC" transform="translate(190, 42)">
        <rect id="apcBox" x="-38" y="-24" width="76" height="48" rx="6" fill="#f1f5f9" stroke="#94a3b8" stroke-width="1.5" filter="url(#subtle-shadow)"/>
        <text x="0" y="-3" text-anchor="middle" font-size="11.5" font-weight="700" fill="#334155">APC/C</text>
        <text id="apcStatus" x="0" y="13" text-anchor="middle" font-size="9.5" font-weight="700" fill="#dc2626">BLOCKED</text>
      </g>

      
      <g id="sacEnzyme" transform="translate(305, 42)">
        
        <rect id="secBox" x="-44" y="-24" width="88" height="22" rx="4" fill="#fee2e2" stroke="#f87171" stroke-width="1.2"/>
        <text id="secText" x="0" y="-9" text-anchor="middle" font-size="10" font-weight="700" fill="#b91c1c">Securin (Bound)</text>
        
        <rect id="sepBox" x="-44" y="2" width="88" height="22" rx="4" fill="#f1f5f9" stroke="#94a3b8" stroke-width="1.2"/>
        <text id="sepText" x="0" y="17" text-anchor="middle" font-size="10" font-weight="700" fill="#64748b">Separase (Off)</text>
      </g>

      
      <path id="sacArrow2" d="M 353 42 L 382 42" stroke="#cbd5e1" stroke-width="2" marker-end="url(#arrow)"/>

      
      <g id="sacChromatid" transform="translate(412, 42)">
        <circle id="chromBg" cx="0" cy="-4" r="22" fill="#f8fafc" stroke="#cbd5e1" stroke-width="1.5" filter="url(#subtle-shadow)"/>
        <text id="chromIcon" x="0" y="2" text-anchor="middle" font-size="15">🔒</text>
        <text id="chromLabel" x="0" y="32" text-anchor="middle" font-size="9.5" font-weight="700" fill="#64748b">Cohesin Intact</text>
      </g>
    </svg>
  </div>

  <script>
    function setState(mode) {
      const btnWait = document.getElementById('btnWait');
      const btnPass = document.getElementById('btnPass');
      
      if (mode === 'wait') {
        btnWait.className = 'tab-btn active-wait';
        btnPass.className = 'tab-btn';
        renderWait();
      } else {
        btnWait.className = 'tab-btn';
        btnPass.className = 'tab-btn active-pass';
        renderPass();
      }
    }

    function renderWait() {
      // --- G2/M Update ---
      document.getElementById('g2Badge').className = 'badge badge-wait';
      document.getElementById('g2Badge').textContent = 'WAIT (DNA INCOMPLETE)';
      
      document.getElementById('regBox').setAttribute('fill', '#fef2f2');
      document.getElementById('regBox').setAttribute('stroke', '#f87171');
      document.getElementById('regTitle').textContent = 'Wee1';
      document.getElementById('regTitle').setAttribute('fill', '#dc2626');
      document.getElementById('regAction').textContent = '+ Inhibitory Ⓟ';
      document.getElementById('regAction').setAttribute('fill', '#991b1b');
      
      document.getElementById('g2Arrow1').setAttribute('stroke', '#f87171');
      document.getElementById('phosphateGroup').setAttribute('display', 'block');
      
      document.getElementById('mpfStatus').textContent = 'Inactive MPF';
      document.getElementById('mpfStatus').setAttribute('fill', '#dc2626');
      
      document.getElementById('g2Arrow2').setAttribute('stroke', '#cbd5e1');
      document.getElementById('g2Arrow2').setAttribute('marker-end', 'url(#arrow)');
      
      document.getElementById('outBox').setAttribute('fill', '#f8fafc');
      document.getElementById('outBox').setAttribute('stroke', '#cbd5e1');
      document.getElementById('outIcon').textContent = '⏸';
      document.getElementById('outText1').textContent = 'G₂ Arrest';
      document.getElementById('outText1').setAttribute('fill', '#64748b');
      document.getElementById('outText2').textContent = 'Repairing DNA';

      // --- SAC Update ---
      document.getElementById('sacBadge').className = 'badge badge-wait';
      document.getElementById('sacBadge').textContent = 'WAIT (NO TENSION)';

      document.getElementById('kinBox').setAttribute('fill', '#fef2f2');
      document.getElementById('kinBox').setAttribute('stroke', '#f87171');
      document.getElementById('kinIcon').textContent = '⚠️';
      document.getElementById('kinText1').textContent = 'Unattached';
      document.getElementById('kinText1').setAttribute('fill', '#dc2626');
      document.getElementById('kinText2').textContent = 'Mad2 Signal';

      document.getElementById('sacArrow1').setAttribute('stroke', '#ef4444');
      document.getElementById('sacInhibitLabel').textContent = '⛔';

      document.getElementById('apcBox').setAttribute('fill', '#f1f5f9');
      document.getElementById('apcBox').setAttribute('stroke', '#94a3b8');
      document.getElementById('apcStatus').textContent = 'BLOCKED';
      document.getElementById('apcStatus').setAttribute('fill', '#dc2626');

      document.getElementById('secBox').setAttribute('fill', '#fee2e2');
      document.getElementById('secBox').setAttribute('stroke', '#f87171');
      document.getElementById('secText').textContent = 'Securin (Bound)';
      document.getElementById('secText').setAttribute('fill', '#b91c1c');

      document.getElementById('sepBox').setAttribute('fill', '#f1f5f9');
      document.getElementById('sepBox').setAttribute('stroke', '#94a3b8');
      document.getElementById('sepText').textContent = 'Separase (Off)';
      document.getElementById('sepText').setAttribute('fill', '#64748b');

      document.getElementById('chromBg').setAttribute('fill', '#f8fafc');
      document.getElementById('chromBg').setAttribute('stroke', '#cbd5e1');
      document.getElementById('chromIcon').textContent = '🔒';
      document.getElementById('chromLabel').textContent = 'Cohesin Intact';
      document.getElementById('chromLabel').setAttribute('fill', '#64748b');
    }

    function renderPass() {
      // --- G2/M Update ---
      document.getElementById('g2Badge').className = 'badge badge-go';
      document.getElementById('g2Badge').textContent = 'PASSED (100% REPLICATED)';
      
      document.getElementById('regBox').setAttribute('fill', '#ecfdf5');
      document.getElementById('regBox').setAttribute('stroke', '#34d399');
      document.getElementById('regTitle').textContent = 'Cdc25';
      document.getElementById('regTitle').setAttribute('fill', '#059669');
      document.getElementById('regAction').textContent = 'Removes Ⓟ';
      document.getElementById('regAction').setAttribute('fill', '#065f46');
      
      document.getElementById('g2Arrow1').setAttribute('stroke', '#10b981');
      document.getElementById('phosphateGroup').setAttribute('display', 'none');
      
      document.getElementById('mpfStatus').textContent = 'Active MPF ⚡';
      document.getElementById('mpfStatus').setAttribute('fill', '#059669');
      
      document.getElementById('g2Arrow2').setAttribute('stroke', '#10b981');
      document.getElementById('g2Arrow2').setAttribute('marker-end', 'url(#arrow-green)');
      
      document.getElementById('outBox').setAttribute('fill', '#ecfdf5');
      document.getElementById('outBox').setAttribute('stroke', '#34d399');
      document.getElementById('outIcon').textContent = '✓';
      document.getElementById('outText1').textContent = 'Mitosis Entry';
      document.getElementById('outText1').setAttribute('fill', '#059669');
      document.getElementById('outText2').textContent = 'Envelope Breakdown';

      // --- SAC Update ---
      document.getElementById('sacBadge').className = 'badge badge-go';
      document.getElementById('sacBadge').textContent = 'PASSED (BIPOLAR TENSION)';

      document.getElementById('kinBox').setAttribute('fill', '#ecfdf5');
      document.getElementById('kinBox').setAttribute('stroke', '#34d399');
      document.getElementById('kinIcon').textContent = '✓';
      document.getElementById('kinText1').textContent = 'All Attached';
      document.getElementById('kinText1').setAttribute('fill', '#059669');
      document.getElementById('kinText2').textContent = 'Mad2 Silenced';

      document.getElementById('sacArrow1').setAttribute('stroke', '#10b981');
      document.getElementById('sacInhibitLabel').textContent = '➔';

      document.getElementById('apcBox').setAttribute('fill', '#ecfdf5');
      document.getElementById('apcBox').setAttribute('stroke', '#34d399');
      document.getElementById('apcStatus').textContent = 'ACTIVE';
      document.getElementById('apcStatus').setAttribute('fill', '#059669');

      document.getElementById('secBox').setAttribute('fill', '#f1f5f9');
      document.getElementById('secBox').setAttribute('stroke', '#cbd5e1');
      document.getElementById('secText').textContent = 'Securin (Degraded)';
      document.getElementById('secText').setAttribute('fill', '#94a3b8');

      document.getElementById('sepBox').setAttribute('fill', '#ecfdf5');
      document.getElementById('sepBox').setAttribute('stroke', '#34d399');
      document.getElementById('sepText').textContent = 'Separase (Active ✂)';
      document.getElementById('sepText').setAttribute('fill', '#059669');

      document.getElementById('chromBg').setAttribute('fill', '#ecfdf5');
      document.getElementById('chromBg').setAttribute('stroke', '#34d399');
      document.getElementById('chromIcon').textContent = '✂';
      document.getElementById('chromLabel').textContent = 'Anaphase Split';
      document.getElementById('chromLabel').setAttribute('fill', '#059669');
    }

    // Initialize in Wait mode
    renderWait();
  </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">
  <title>Eukaryotic Cell Cycle & Checkpoints</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: #0f172a;
      width: 100%;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 8px 10px;
      user-select: none;
    }

    .nav-bar {
      display: flex;
      flex-wrap: wrap;
      gap: 4px;
      justify-content: center;
      width: 100%;
      max-width: 500px;
      margin-bottom: 4px;
    }

    .pill-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 16px;
      padding: 4px 9px;
      font-size: 12px;
      font-weight: 600;
      color: #334155;
      cursor: pointer;
      transition: background 0.15s, color 0.15s, border-color 0.15s;
    }

    .pill-btn:hover {
      background: #e2e8f0;
      color: #0f172a;
    }

    .pill-btn.active {
      background: #0f172a;
      color: #ffffff;
      border-color: #0f172a;
    }

    .diagram-area {
      position: relative;
      width: 100%;
      max-width: 420px;
      aspect-ratio: 500 / 400;
      margin: 0 auto;
    }

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

    .sector {
      cursor: pointer;
      transition: opacity 0.2s ease, filter 0.2s ease;
    }

    .sector:hover {
      filter: brightness(1.05);
    }

    .sector.dimmed {
      opacity: 0.22;
    }

    .checkpoint-node {
      cursor: pointer;
      transition: opacity 0.2s ease, filter 0.2s ease;
    }

    .checkpoint-node:hover {
      filter: brightness(1.15);
    }

    .checkpoint-node.dimmed {
      opacity: 0.2;
    }

    .center-hub {
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      width: 118px;
      height: 118px;
      border-radius: 50%;
      background: #ffffff;
      box-shadow: 0 2px 10px rgba(0, 0, 0, 0.08);
      border: 2px solid #e2e8f0;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      text-align: center;
      pointer-events: none;
      padding: 4px;
    }

    .hub-badge {
      font-size: 19px;
      font-weight: 800;
      line-height: 1.1;
      color: #0284c7;
    }

    .hub-title {
      font-size: 12px;
      font-weight: 700;
      color: #0f172a;
      margin-top: 2px;
      line-height: 1.2;
    }

    .hub-dna {
      display: inline-block;
      margin-top: 3px;
      font-size: 10.5px;
      font-weight: 700;
      padding: 1px 6px;
      border-radius: 8px;
      background: #f1f5f9;
      color: #334155;
    }

    /* Pedagogical Card */
    .info-card {
      width: 100%;
      max-width: 460px;
      margin-top: 4px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 8px 12px;
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 6px 10px;
      font-size: 12.5px;
    }

    .info-item {
      display: flex;
      flex-direction: column;
    }

    .info-label {
      font-size: 10.5px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #475569;
      margin-bottom: 2px;
    }

    .info-val {
      font-weight: 600;
      color: #0f172a;
      line-height: 1.3;
    }

    .span-2 {
      grid-column: span 2;
    }

    .status-pill {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      font-size: 12px;
      font-weight: 700;
      color: #0f172a;
    }

    .status-dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: #0284c7;
      flex-shrink: 0;
    }

    @media (max-width: 400px) {
      .pill-btn {
        font-size: 11px;
        padding: 3px 7px;
      }
      .info-card {
        grid-template-columns: 1fr;
        padding: 7px 10px;
      }
      .span-2 {
        grid-column: span 1;
      }
      .center-hub {
        width: 104px;
        height: 104px;
      }
      .hub-badge {
        font-size: 17px;
      }
      .hub-title {
        font-size: 11px;
      }
    }
  </style>
</head>
<body>

  
  <div class="nav-bar">
    <button class="pill-btn active" data-target="g1">G₁ Phase</button>
    <button class="pill-btn" data-target="s">S Phase</button>
    <button class="pill-btn" data-target="g2">G₂ Phase</button>
    <button class="pill-btn" data-target="m">M Phase</button>
    <button class="pill-btn" data-target="g0">G₀ Resting</button>
    <button class="pill-btn" data-target="cp1">G₁/S Gate</button>
    <button class="pill-btn" data-target="cp2">G₂/M Gate</button>
    <button class="pill-btn" data-target="cp3">SAC Gate</button>
  </div>

  
  <div class="diagram-area">
    <svg viewBox="0 0 500 400" id="cycleSvg">
      <defs>
        <marker id="arrowG0" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1 L 10 5 L 0 9 z" fill="#475569"/>
        </marker>
        <filter id="badgeShadow" x="-20%" y="-20%" width="140%" height="140%">
          <feDropShadow dx="0" dy="1.5" stdDeviation="2" flood-opacity="0.25"/>
        </filter>
      </defs>

      
      <path id="interphaseArc" d="" fill="none" stroke="#64748b" stroke-width="2.5" stroke-dasharray="4 3"/>
      <text x="250" y="24" text-anchor="middle" fill="#334155" font-size="12" font-weight="700" letter-spacing="1">INTERPHASE (~90% OF DURATION)</text>

      
      <g id="g0Group" class="sector" onclick="selectItem('g0')">
        <path d="M 370 175 C 410 175, 410 120, 425 105" fill="none" stroke="#475569" stroke-width="2.5" stroke-dasharray="4 3" marker-end="url(#arrowG0)"/>
        <rect x="355" y="62" width="135" height="42" rx="8" fill="#f8fafc" stroke="#64748b" stroke-width="1.5"/>
        <text x="422" y="80" text-anchor="middle" font-size="12" font-weight="700" fill="#0f172a">G₀ Phase</text>
        <text x="422" y="94" text-anchor="middle" font-size="10" font-weight="600" fill="#334155">Quiescence / Exit</text>
      </g>

      
      <g id="sectorsGroup"></g>

      
      <g id="checkpointsGroup"></g>
    </svg>

    
    <div class="center-hub" id="centerHub">
      <span class="hub-badge" id="hubSymbol">G₁</span>
      <span class="hub-title" id="hubTitle">Growth Phase</span>
      <span class="hub-dna" id="hubDna">DNA: 2C</span>
    </div>
  </div>

  
  <div class="info-card">
    <div class="info-item">
      <div class="info-label">Active Focus</div>
      <div class="status-pill">
        <span class="status-dot" id="dotColor"></span>
        <span id="cardName">G₁ Phase (Gap 1)</span>
      </div>
    </div>
    <div class="info-item">
      <div class="info-label">Cellular Activity</div>
      <div class="info-val" id="cardMission">Cell growth, organelle replication</div>
    </div>
    <div class="info-item span-2">
      <div class="info-label">Key Molecular Criteria / Gate Check</div>
      <div class="info-val" id="cardCriteria">Adequate cell size, nutrients, energy, and undamaged DNA template.</div>
    </div>
  </div>

  <script>
    const CX = 250;
    const CY = 200;
    const R_OUTER = 155;
    const R_INNER = 95;

    // Angle definitions (0 deg is top, clockwise)
    const phases = {
      g1: {
        id: 'g1',
        title: 'G₁ Phase',
        subtitle: 'Presynthetic Growth',
        symbol: 'G₁',
        dna: '2C (Diploid)',
        color: '#0284c7',
        fill: '#38bdf8',
        startDeg: 0,
        endDeg: 144,
        mission: 'Cell growth & protein synthesis',
        criteria: 'Evaluates size, nutrient reserves, growth signals, and DNA integrity before committing to divide.',
        midDeg: 72
      },
      s: {
        id: 's',
        title: 'S Phase',
        subtitle: 'DNA Synthesis',
        symbol: 'S',
        dna: '2C → 4C',
        color: '#0d9488',
        fill: '#2dd4bf',
        startDeg: 144,
        endDeg: 270,
        mission: 'DNA Replication & centrosome duplication',
        criteria: 'Faithfully copies every chromosome exactly once; sister chromatids linked by cohesin.',
        midDeg: 207
      },
      g2: {
        id: 'g2',
        title: 'G₂ Phase',
        subtitle: 'Premitotic Gap',
        symbol: 'G₂',
        dna: '4C (Replicated)',
        color: '#4f46e5',
        fill: '#818cf8',
        startDeg: 270,
        endDeg: 324,
        mission: 'Final prep & tubulin synthesis',
        criteria: 'Rapid growth, energy storage, enzyme synthesis needed for chromosome segregation.',
        midDeg: 297
      },
      m: {
        id: 'm',
        title: 'M Phase',
        subtitle: 'Mitosis & Cytokinesis',
        symbol: 'M',
        dna: '4C → 2C',
        color: '#ea580c',
        fill: '#fb923c',
        startDeg: 324,
        endDeg: 360,
        mission: 'Nuclear & cytoplasmic division',
        criteria: 'Prophase, Metaphase, Anaphase, Telophase followed by physical cleavage into 2 daughter cells.',
        midDeg: 342
      },
      g0: {
        id: 'g0',
        title: 'G₀ Phase',
        subtitle: 'Quiescence / Resting',
        symbol: 'G₀',
        dna: '2C (Non-dividing)',
        color: '#334155',
        fill: '#94a3b8',
        mission: 'Metabolic maintenance / differentiated function',
        criteria: 'Reversible exit (e.g., hepatocytes upon injury) or terminal differentiation (e.g., mature neurons).'
      }
    };

    const checkpoints = {
      cp1: {
        id: 'cp1',
        name: 'G₁ / Restriction Point',
        deg: 134,
        color: '#d97706',
        symbol: 'CP₁',
        phase: 'g1',
        title: 'G₁ Checkpoint (Restriction)',
        dna: '2C Gate',
        mission: 'Point of no return for division',
        criteria: 'Checks cell size, nutrients, and DNA damage. Passes to S-phase or halts into G₀.'
      },
      cp2: {
        id: 'cp2',
        name: 'G₂/M Transition Checkpoint',
        deg: 324,
        color: '#dc2626',
        symbol: 'CP₂',
        phase: 'g2',
        title: 'G₂/M DNA Gate',
        dna: '4C Gate',
        mission: 'Replication completion check',
        criteria: 'Halts mitosis if DNA replication is incomplete or DNA damage is detected, activating repair enzymes.'
      },
      cp3: {
        id: 'cp3',
        name: 'Spindle Assembly Checkpoint (SAC)',
        deg: 342,
        color: '#db2777',
        symbol: 'SAC',
        phase: 'm',
        title: 'Spindle Checkpoint (Metaphase)',
        dna: '4C → 2C Gate',
        mission: 'Chromosome alignment verification',
        criteria: 'Ensures all sister chromatids are properly attached to bipolar spindle microtubules before anaphase.'
      }
    };

    let activeId = 'g1';

    function polarToCartesian(cx, cy, r, deg) {
      const rad = ((deg - 90) * Math.PI) / 180.0;
      return {
        x: cx + r * Math.cos(rad),
        y: cy + r * Math.sin(rad)
      };
    }

    function describeDonutSector(cx, cy, rIn, rOut, startDeg, endDeg) {
      const p1 = polarToCartesian(cx, cy, rOut, startDeg);
      const p2 = polarToCartesian(cx, cy, rOut, endDeg);
      const p3 = polarToCartesian(cx, cy, rIn, endDeg);
      const p4 = polarToCartesian(cx, cy, rIn, startDeg);

      const largeArc = endDeg - startDeg <= 180 ? '0' : '1';

      return [
        `M ${p1.x} ${p1.y}`,
        `A ${rOut} ${rOut} 0 ${largeArc} 1 ${p2.x} ${p2.y}`,
        `L ${p3.x} ${p3.y}`,
        `A ${rIn} ${rIn} 0 ${largeArc} 0 ${p4.x} ${p4.y}`,
        'Z'
      ].join(' ');
    }

    function initSVG() {
      const sectorsGroup = document.getElementById('sectorsGroup');
      const checkpointsGroup = document.getElementById('checkpointsGroup');

      // Interphase outer arc (from 0 to 324 deg, radius 170)
      const arcP1 = polarToCartesian(CX, CY, 170, 2);
      const arcP2 = polarToCartesian(CX, CY, 170, 322);
      document.getElementById('interphaseArc').setAttribute('d', `M ${arcP1.x} ${arcP1.y} A 170 170 0 1 1 ${arcP2.x} ${arcP2.y}`);

      // Render 4 main phase sectors
      ['g1', 's', 'g2', 'm'].forEach(key => {
        const p = phases[key];
        const pathData = describeDonutSector(CX, CY, R_INNER, R_OUTER, p.startDeg, p.endDeg);

        const g = document.createElementNS('http://www.w3.org/2000/svg', 'g');
        g.setAttribute('class', 'sector');
        g.setAttribute('id', `sector-${key}`);
        g.onclick = () => selectItem(key);

        const path = document.createElementNS('http://www.w3.org/2000/svg', 'path');
        path.setAttribute('d', pathData);
        path.setAttribute('fill', p.fill);
        path.setAttribute('stroke', '#ffffff');
        path.setAttribute('stroke-width', '3');

        // Sector label with high contrast dark slate text
        const labelPos = polarToCartesian(CX, CY, (R_INNER + R_OUTER) / 2, p.midDeg);
        const text = document.createElementNS('http://www.w3.org/2000/svg', 'text');
        text.setAttribute('x', labelPos.x);
        text.setAttribute('y', labelPos.y + 6);
        text.setAttribute('text-anchor', 'middle');
        text.setAttribute('fill', '#0f172a');
        text.setAttribute('font-size', '16');
        text.setAttribute('font-weight', '800');
        text.style.pointerEvents = 'none';
        text.textContent = p.symbol;

        g.appendChild(path);
        g.appendChild(text);
        sectorsGroup.appendChild(g);
      });

      // Render 3 Checkpoints
      Object.keys(checkpoints).forEach(k => {
        const cp = checkpoints[k];
        const pos = polarToCartesian(CX, CY, (R_INNER + R_OUTER) / 2, cp.deg);

        const g = document.createElementNS('http://www.w3.org/2000/svg', 'g');
        g.setAttribute('class', 'checkpoint-node');
        g.setAttribute('id', `node-${k}`);
        g.setAttribute('transform', `translate(${pos.x}, ${pos.y})`);
        g.onclick = (e) => {
          e.stopPropagation();
          selectItem(k);
        };

        const poly = document.createElementNS('http://www.w3.org/2000/svg', 'polygon');
        poly.setAttribute('points', '0,-14 13,-4 13,8 0,16 -13,8 -13,-4');
        poly.setAttribute('fill', cp.color);
        poly.setAttribute('stroke', '#ffffff');
        poly.setAttribute('stroke-width', '2');
        poly.setAttribute('filter', 'url(#badgeShadow)');

        const text = document.createElementNS('http://www.w3.org/2000/svg', 'text');
        text.setAttribute('x', '0');
        text.setAttribute('y', '3.5');
        text.setAttribute('text-anchor', 'middle');
        text.setAttribute('fill', '#ffffff');
        text.setAttribute('font-size', '9');
        text.setAttribute('font-weight', '800');
        text.textContent = cp.symbol;

        g.appendChild(poly);
        g.appendChild(text);
        checkpointsGroup.appendChild(g);
      });
    }

    function selectItem(id) {
      activeId = id;

      // Update pills
      document.querySelectorAll('.pill-btn').forEach(b => {
        b.classList.toggle('active', b.dataset.target === id);
      });

      const isCheckpoint = id.startsWith('cp');
      const data = isCheckpoint ? checkpoints[id] : phases[id];

      // Update center hub
      document.getElementById('hubSymbol').textContent = data.symbol;
      document.getElementById('hubSymbol').style.color = data.color;
      document.getElementById('hubTitle').textContent = isCheckpoint ? data.name.split(' ')[0] : data.title;
      document.getElementById('hubDna').textContent = isCheckpoint ? data.dna : `DNA: ${data.dna}`;

      // Update banner card
      document.getElementById('dotColor').style.background = data.color;
      document.getElementById('cardName').textContent = isCheckpoint ? data.name : `${data.title} (${data.subtitle || ''})`;
      document.getElementById('cardMission').textContent = data.mission;
      document.getElementById('cardCriteria').textContent = data.criteria;

      // Dimming logic
      ['g1', 's', 'g2', 'm'].forEach(k => {
        const sector = document.getElementById(`sector-${k}`);
        if (!sector) return;
        if (isCheckpoint) {
          sector.classList.toggle('dimmed', checkpoints[id].phase !== k);
        } else {
          sector.classList.toggle('dimmed', id !== 'g0' && id !== k);
        }
      });

      const g0El = document.getElementById('g0Group');
      if (g0El) {
        g0El.classList.toggle('dimmed', id !== 'g0');
      }

      Object.keys(checkpoints).forEach(k => {
        const node = document.getElementById(`node-${k}`);
        if (!node) return;
        node.classList.toggle('dimmed', isCheckpoint && k !== id);
      });
    }

    // Bind navigation buttons
    document.querySelectorAll('.pill-btn').forEach(btn => {
      btn.addEventListener('click', () => {
        selectItem(btn.dataset.target);
      });
    });

    initSVG();
    selectItem('g1');
  </script>
</body>
</html>

OGS.11.LS.CB.5

Aligned learning resources

Related diagrams