<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Plant Cell Adaptations & Meristems</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8fafc;
      color: #0f172a;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 8px;
      gap: 8px;
      user-select: none;
      width: 100%;
      max-width: 620px;
      margin: 0 auto;
    }

    .header-badge {
      font-size: 11px;
      font-weight: 700;
      color: #14532d;
      background: #dcfce7;
      border: 1px solid #86efac;
      padding: 4px 12px;
      border-radius: 999px;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .pulse-dot {
      width: 8px;
      height: 8px;
      background: #16a34a;
      border-radius: 50%;
      box-shadow: 0 0 0 0 rgba(22, 163, 74, 0.7);
      animation: pulse 2s cubic-bezier(0.4, 0, 0.6, 1) infinite;
    }

    @keyframes pulse {
      0% { box-shadow: 0 0 0 0 rgba(22, 163, 74, 0.7); }
      70% { box-shadow: 0 0 0 6px rgba(22, 163, 74, 0); }
      100% { box-shadow: 0 0 0 0 rgba(22, 163, 74, 0); }
    }

    /* Top plant diagram */
    .top-panel {
      width: 100%;
      height: 88px;
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 10px;
      display: flex;
      align-items: center;
      justify-content: space-around;
      padding: 4px 8px;
    }

    .meristem-marker {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 2px;
      font-size: 11px;
      font-weight: 700;
      color: #14532d;
      text-align: center;
    }

    .meristem-tag {
      background: #fef08a;
      border: 1px solid #eab308;
      color: #713f12;
      padding: 1px 6px;
      border-radius: 4px;
      font-size: 9px;
      font-weight: 700;
    }

    /* Bottom cells grid */
    .cells-grid {
      width: 100%;
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 8px;
    }

    .cell-card {
      background: #ffffff;
      border: 2px solid #cbd5e1;
      border-radius: 10px;
      padding: 6px 4px;
      display: flex;
      flex-direction: column;
      align-items: center;
      cursor: pointer;
      transition: border-color 0.5s ease, background-color 0.5s ease;
      min-height: 220px;
      justify-content: space-between;
    }

    .cell-card:hover {
      border-color: #0284c7;
    }

    .cell-card.active {
      border-color: #0284c7;
      background: #f0f9ff;
    }

    .cell-title {
      font-size: 11px;
      font-weight: 800;
      color: #0f172a;
      text-align: center;
      line-height: 1.2;
    }

    .cell-visual {
      width: 100%;
      height: 115px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .cell-desc {
      font-size: 10px;
      font-weight: 600;
      color: #334155;
      text-align: center;
      line-height: 1.2;
      min-height: 38px;
      display: flex;
      align-items: center;
      justify-content: center;
      padding: 0 2px;
    }

    .cell-card.active .cell-desc {
      color: #0369a1;
      font-weight: 700;
    }

    /* Active Details Banner */
    .detail-banner {
      width: 100%;
      background: #ffffff;
      border-left: 4px solid #0284c7;
      border-top: 1px solid #e2e8f0;
      border-right: 1px solid #e2e8f0;
      border-bottom: 1px solid #e2e8f0;
      border-radius: 6px;
      padding: 6px 10px;
      font-size: 11px;
      color: #1e293b;
      line-height: 1.35;
    }
    .detail-banner strong {
      color: #0369a1;
    }

    /* SVG styling */
    svg {
      overflow: visible;
      max-width: 100%;
      height: auto;
    }

    .flow-arrow {
      stroke: #0284c7;
      stroke-dasharray: 4 3;
      animation: flowUp 2s linear infinite;
    }

    @keyframes flowUp {
      from { stroke-dashoffset: 14; }
      to { stroke-dashoffset: 0; }
    }

    /* Mobile Responsive Layout (under 500px) */
    @media (max-width: 500px) {
      body {
        padding: 6px;
        gap: 6px;
      }
      .top-panel {
        height: 80px;
      }
      .cells-grid {
        grid-template-columns: 1fr;
        gap: 6px;
      }
      .cell-card {
        flex-direction: row;
        min-height: 76px;
        padding: 6px 10px;
        justify-content: flex-start;
        gap: 10px;
      }
      .cell-visual {
        width: 70px;
        height: 64px;
        flex-shrink: 0;
      }
      .cell-text-group {
        display: flex;
        flex-direction: column;
        align-items: flex-start;
        text-align: left;
        flex: 1;
      }
      .cell-title {
        text-align: left;
        font-size: 12px;
      }
      .cell-title br {
        display: none;
      }
      .cell-desc {
        text-align: left;
        min-height: unset;
        font-size: 10.5px;
        margin-top: 2px;
      }
    }
  </style>
</head>
<body>

  
  <div class="header-badge">
    <div class="pulse-dot"></div>
    Apical Meristems (Continuous Differentiation)
  </div>

  <div class="top-panel">
    
    <div class="meristem-marker">
      <span>🌿 Shoot Tip</span>
      <span class="meristem-tag">Meristem</span>
    </div>

    
    <svg width="130" height="78" viewBox="0 0 130 78" aria-label="Plant shoot and root meristem diagram">
      
      <line x1="15" y1="42" x2="115" y2="42" stroke="#475569" stroke-width="1.5" stroke-dasharray="3 3" />
      <text x="96" y="38" font-size="9" fill="#334155" font-weight="700">Soil</text>

      
      <path d="M65,42 L65,14" stroke="#22c55e" stroke-width="5" stroke-linecap="round" />
      
      
      <path d="M65,28 Q48,18 42,24 Q52,36 65,30" fill="#16a34a" />
      <path d="M65,24 Q82,14 88,20 Q78,32 65,26" fill="#16a34a" />

      
      <circle cx="65" cy="12" r="7" fill="#fef08a" stroke="#ca8a04" stroke-width="2" />
      <circle cx="65" cy="12" r="2.5" fill="#854d0e" />

      
      <path d="M65,42 L65,68" stroke="#64748b" stroke-width="3.5" stroke-linecap="round" />
      <path d="M65,50 Q52,56 44,60" stroke="#64748b" stroke-width="1.5" stroke-linecap="round" fill="none" />
      <path d="M65,54 Q78,60 86,63" stroke="#64748b" stroke-width="1.5" stroke-linecap="round" fill="none" />

      
      <circle cx="65" cy="69" r="7" fill="#fef08a" stroke="#ca8a04" stroke-width="2" />
      <circle cx="65" cy="69" r="2.5" fill="#854d0e" />
    </svg>

    
    <div class="meristem-marker">
      <span class="meristem-tag">Meristem</span>
      <span>🌱 Root Tip</span>
    </div>
  </div>

  
  <div class="cells-grid">

    
    <div class="cell-card active" onclick="selectCell(0)">
      <div class="cell-visual">
        <svg width="115" height="100" viewBox="0 0 115 100">
          
          <path d="M 12,18 C 12,14 55,14 55,18 L 55,38 C 76,38 78,50 78,56 C 78,62 76,74 55,74 L 55,82 C 55,86 12,86 12,82 Z"
                fill="#f1f5f9" stroke="#475569" stroke-width="2" />
          
          
          <path d="M 18,24 L 49,24 L 49,43 C 71,43 71,53 71,56 C 71,59 71,69 49,69 L 49,76 L 18,76 Z"
                fill="#e0f2fe" stroke="#0284c7" stroke-width="1.2" stroke-dasharray="3 2" />

          
          <ellipse cx="30" cy="40" rx="7" ry="9" fill="#cbd5e1" stroke="#334155" stroke-width="1.2" />
          <circle cx="30" cy="40" r="2.5" fill="#1e293b" />

          
          <g fill="#e11d48" stroke="#9f1239" stroke-width="0.8">
            <ellipse cx="26" cy="64" rx="4.5" ry="2.5" transform="rotate(-15 26 64)" />
            <ellipse cx="42" cy="32" rx="4" ry="2.5" transform="rotate(30 42 32)" />
            <ellipse cx="64" cy="56" rx="4.5" ry="2.5" />
          </g>

          
          <g font-size="8.5" font-weight="800" fill="#0369a1">
            <text x="80" y="47">H₂O →</text>
            <text x="80" y="68">Min →</text>
          </g>
        </svg>
      </div>
      <div class="cell-text-group">
        <div class="cell-title">Root Hair Cell</div>
        <div class="cell-desc">Massive surface area for water & mineral uptake</div>
      </div>
    </div>

    
    <div class="cell-card" onclick="selectCell(1)">
      <div class="cell-visual">
        <svg width="100" height="100" viewBox="0 0 100 100">
          
          <rect x="25" y="8" width="50" height="84" rx="3" fill="#fefce8" stroke="#92400e" stroke-width="2.5" />
          
          
          <rect x="33" y="8" width="34" height="84" fill="#f8fafc" />

          
          <path d="M 25,22 Q 50,30 75,22" stroke="#b45309" stroke-width="3.5" fill="none" stroke-linecap="round" />
          <path d="M 25,42 Q 50,50 75,42" stroke="#b45309" stroke-width="3.5" fill="none" stroke-linecap="round" />
          <path d="M 25,62 Q 50,70 75,62" stroke="#b45309" stroke-width="3.5" fill="none" stroke-linecap="round" />
          <path d="M 25,80 Q 50,88 75,80" stroke="#b45309" stroke-width="3.5" fill="none" stroke-linecap="round" />

          
          <line x1="50" y1="84" x2="50" y2="16" class="flow-arrow" stroke-width="2.5" />
          <polygon points="50,10 46,18 54,18" fill="#0284c7" />
        </svg>
      </div>
      <div class="cell-text-group">
        <div class="cell-title">Xylem Vessel</div>
        <div class="cell-desc">Lignin strengthens walls; hollow lumen allows flow</div>
      </div>
    </div>

    
    <div class="cell-card" onclick="selectCell(2)">
      <div class="cell-visual">
        <svg width="100" height="100" viewBox="0 0 100 100">
          
          <g stroke="#ca8a04" stroke-width="1.8" stroke-linecap="round">
            <line x1="38" y1="3" x2="38" y2="8" />
            <line x1="50" y1="1" x2="50" y2="8" />
            <line x1="62" y1="3" x2="62" y2="8" />
          </g>

          
          <rect x="28" y="10" width="44" height="82" rx="4" fill="#f0fdf4" stroke="#15803d" stroke-width="2.2" />
          
          
          <rect x="36" y="30" width="28" height="46" rx="3" fill="#e0f2fe" opacity="0.75" />

          
          <g fill="#15803d" stroke="#14532d" stroke-width="0.7">
            <ellipse cx="35" cy="18" rx="3.5" ry="2.5" />
            <ellipse cx="44" cy="17" rx="3.5" ry="2.5" />
            <ellipse cx="55" cy="17" rx="3.5" ry="2.5" />
            <ellipse cx="64" cy="19" rx="3.5" ry="2.5" />
            
            <ellipse cx="33" cy="28" rx="3" ry="3.5" />
            <ellipse cx="67" cy="30" rx="3" ry="3.5" />
            <ellipse cx="33" cy="44" rx="3" ry="3.5" />
            <ellipse cx="67" cy="46" rx="3" ry="3.5" />
            <ellipse cx="33" cy="60" rx="3" ry="3.5" />
            <ellipse cx="67" cy="62" rx="3" ry="3.5" />

            <ellipse cx="38" cy="84" rx="3.5" ry="2.5" />
            <ellipse cx="50" cy="85" rx="3.5" ry="2.5" />
            <ellipse cx="62" cy="84" rx="3.5" ry="2.5" />
          </g>

          
          <circle cx="50" cy="64" r="5" fill="#86efac" stroke="#166534" stroke-width="1" />
        </svg>
      </div>
      <div class="cell-text-group">
        <div class="cell-title">Palisade Mesophyll</div>
        <div class="cell-desc">Positioned at top of leaf to absorb maximum light</div>
      </div>
    </div>

  </div>

  
  <div class="detail-banner" id="detail-banner">
    <strong>Root Hair Cell:</strong> Long projection maximizes surface area for rapid absorption of water & minerals. Contains no chloroplasts (underground).
  </div>

  <script>
    const cards = document.querySelectorAll('.cell-card');
    const banner = document.getElementById('detail-banner');
    
    const cellDetails = [
      {
        title: "Root Hair Cell",
        desc: "Long finger-like projection maximizes surface area for rapid water & mineral uptake. Packed with mitochondria for active transport; no chloroplasts."
      },
      {
        title: "Xylem Vessel",
        desc: "Hollow, continuous dead tubes reinforced with waterproof lignin spirals. Transports water and dissolved mineral ions via bulk transpiration pull."
      },
      {
        title: "Palisade Mesophyll",
        desc: "Tall, columnar cells packed with chloroplasts near the upper leaf surface to maximize light absorption for photosynthesis."
      }
    ];

    function selectCell(idx) {
      cards.forEach((c, i) => {
        if (i === idx) {
          c.classList.add('active');
        } else {
          c.classList.remove('active');
        }
      });
      banner.innerHTML = `<strong>${cellDetails[idx].title}:</strong> ${cellDetails[idx].desc}`;
    }
  </script>
</body>
</html>

Cell Differentiation in Developing Organisms

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="1:1">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8fafc;
      color: #1e293b;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
    }

    .diagram-grid {
      width: 100%;
      max-width: 580px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      margin: 0 auto;
    }

    /* Top: Stem cell */
    .stem-panel {
      background: #ffffff;
      border: 2px solid #cbd5e1;
      border-radius: 12px;
      padding: 10px 14px;
      text-align: center;
      box-shadow: 0 2px 4px rgba(0,0,0,0.04);
    }

    .cell-header {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 15px;
      font-weight: 700;
      color: #0f172a;
      margin-bottom: 8px;
    }

    .cell-badge {
      display: inline-block;
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      padding: 2px 8px;
      border-radius: 12px;
      letter-spacing: 0.5px;
    }

    .badge-stem { background: #e0f2fe; color: #0284c7; }
    .badge-rbc { background: #ffe4e6; color: #e11d48; }
    .badge-muscle { background: #ccfbf1; color: #0f766e; }

    /* Genome Strips */
    .genome-strip {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 6px;
      background: #f1f5f9;
      padding: 6px;
      border-radius: 8px;
      border: 1px solid #e2e8f0;
    }

    .gene-box {
      border-radius: 6px;
      padding: 6px 4px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 3px;
      font-size: 12px;
      font-weight: 600;
      transition: all 0.3s ease;
      min-height: 48px;
      text-align: center;
      line-height: 1.1;
    }

    .gene-status {
      font-size: 10px;
      font-weight: 700;
      letter-spacing: 0.3px;
      display: flex;
      align-items: center;
      gap: 2px;
    }

    /* Gene specific colors */
    .g-hemo { background: #ffe4e6; border: 1.5px solid #f43f5e; color: #9f1239; }
    .g-myo  { background: #ccfbf1; border: 1.5px solid #14b8a6; color: #115e59; }
    .g-ker  { background: #fef3c7; border: 1.5px solid #f59e0b; color: #92400e; }
    .g-neu  { background: #ede9fe; border: 1.5px solid #8b5cf6; color: #5b21b6; }

    /* Silenced state */
    .gene-box.silenced {
      background: #f1f5f9 !important;
      border: 1.5px dashed #cbd5e1 !important;
      color: #94a3b8 !important;
      opacity: 0.65;
    }

    /* Active highlighted state */
    .gene-box.active {
      box-shadow: 0 0 0 2px #ffffff, 0 0 0 4px #0284c7;
      font-weight: 700;
      transform: translateY(-1px);
    }

    .gene-box.active.g-hemo {
      box-shadow: 0 0 0 2px #ffffff, 0 0 0 4px #e11d48;
      background: #ffe4e6;
    }

    .gene-box.active.g-myo {
      box-shadow: 0 0 0 2px #ffffff, 0 0 0 4px #0d9488;
      background: #ccfbf1;
    }

    /* Fork Branch Visual */
    .fork-container {
      display: flex;
      justify-content: space-around;
      align-items: center;
      padding: 0 20px;
      height: 24px;
      position: relative;
    }

    .fork-svg {
      width: 100%;
      height: 24px;
    }

    /* Pathways side-by-side */
    .pathways-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 10px;
    }

    .diff-card {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 8px;
      box-shadow: 0 2px 4px rgba(0,0,0,0.03);
    }

    .diff-card.active-rbc {
      border-color: #fecdd3;
    }

    .diff-card.active-muscle {
      border-color: #99f6e4;
    }

    .cell-preview {
      display: flex;
      align-items: center;
      gap: 8px;
      background: #f8fafc;
      padding: 6px 8px;
      border-radius: 8px;
      font-size: 13px;
      font-weight: 600;
    }

    .cell-icon {
      font-size: 20px;
      line-height: 1;
    }

    .cell-function {
      font-size: 11px;
      color: #64748b;
      font-weight: 500;
    }

    .mini-genome {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 4px;
    }

    .mini-gene {
      border-radius: 5px;
      padding: 4px 2px;
      font-size: 10px;
      font-weight: 700;
      text-align: center;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 2px;
    }

    /* Core takeaway banner */
    .takeaway-banner {
      background: #eff6ff;
      border: 1.5px solid #bfdbfe;
      border-radius: 10px;
      padding: 8px 12px;
      font-size: 12px;
      color: #1e40af;
      display: flex;
      align-items: center;
      gap: 8px;
      line-height: 1.35;
    }

    .takeaway-icon {
      font-size: 18px;
      flex-shrink: 0;
    }

    /* Interactive toggle bar */
    .controls {
      display: flex;
      justify-content: center;
      gap: 8px;
      width: 100%;
      max-width: 580px;
      margin-bottom: 6px;
    }

    .btn-tab {
      flex: 1;
      padding: 6px 8px;
      border: 1.5px solid #cbd5e1;
      background: #ffffff;
      border-radius: 8px;
      font-size: 12px;
      font-weight: 700;
      color: #475569;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 4px;
      transition: all 0.2s ease;
    }

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

    @media (max-width: 400px) {
      .pathways-grid {
        grid-template-columns: 1fr;
      }
      .gene-box {
        font-size: 10px;
        min-height: 42px;
      }
      .gene-status {
        font-size: 9px;
      }
    }
  </style>
</head>
<body>

  <div class="controls">
    <button class="btn-tab active" id="btnAll" onclick="setFocus('all')">✦ Overview</button>
    <button class="btn-tab" id="btnRBC" onclick="setFocus('rbc')">🔴 Red Blood Cell</button>
    <button class="btn-tab" id="btnMuscle" onclick="setFocus('muscle')">💪 Muscle Cell</button>
  </div>

  <div class="diagram-grid">
    
    <div class="stem-panel" id="panelStem">
      <div class="cell-header">
        <span>🔬 Unspecialized Stem Cell</span>
        <span class="cell-badge badge-stem">All Genes Present</span>
      </div>
      <div class="genome-strip">
        <div class="gene-box g-hemo">
          <span>Hemoglobin</span>
          <span class="gene-status">🧬 Gene 1</span>
        </div>
        <div class="gene-box g-myo">
          <span>Actin / Myosin</span>
          <span class="gene-status">🧬 Gene 2</span>
        </div>
        <div class="gene-box g-ker">
          <span>Keratin</span>
          <span class="gene-status">🧬 Gene 3</span>
        </div>
        <div class="gene-box g-neu">
          <span>Neurotrans.</span>
          <span class="gene-status">🧬 Gene 4</span>
        </div>
      </div>
    </div>

    
    <div class="fork-container">
      <svg class="fork-svg" viewBox="0 0 400 24" preserveAspectRatio="none">
        <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 L 10 5 L 0 9 z" fill="#94a3b8"/>
          </marker>
        </defs>
        <path d="M 200 0 L 200 6 L 100 6 L 100 20" fill="none" stroke="#94a3b8" stroke-width="2" stroke-dasharray="4 2" marker-end="url(#arrow)"/>
        <path d="M 200 0 L 200 6 L 300 6 L 300 20" fill="none" stroke="#94a3b8" stroke-width="2" stroke-dasharray="4 2" marker-end="url(#arrow)"/>
      </svg>
    </div>

    
    <div class="pathways-grid">
      
      <div class="diff-card active-rbc" id="cardRBC">
        <div class="cell-preview">
          <span class="cell-icon">🔴</span>
          <div>
            <div>Red Blood Cell</div>
            <div class="cell-function">Transports O₂</div>
          </div>
        </div>

        <div class="mini-genome">
          <div class="gene-box mini-gene g-hemo active">
            <span>Hemo</span>
            <span class="gene-status">ON ✓</span>
          </div>
          <div class="gene-box mini-gene silenced">
            <span>Myo</span>
            <span class="gene-status">OFF 🔒</span>
          </div>
          <div class="gene-box mini-gene silenced">
            <span>Ker</span>
            <span class="gene-status">OFF 🔒</span>
          </div>
          <div class="gene-box mini-gene silenced">
            <span>Neu</span>
            <span class="gene-status">OFF 🔒</span>
          </div>
        </div>
      </div>

      
      <div class="diff-card active-muscle" id="cardMuscle">
        <div class="cell-preview">
          <span class="cell-icon">💪</span>
          <div>
            <div>Muscle Cell</div>
            <div class="cell-function">Contracts & Moves</div>
          </div>
        </div>

        <div class="mini-genome">
          <div class="gene-box mini-gene silenced">
            <span>Hemo</span>
            <span class="gene-status">OFF 🔒</span>
          </div>
          <div class="gene-box mini-gene g-myo active">
            <span>Myo</span>
            <span class="gene-status">ON ✓</span>
          </div>
          <div class="gene-box mini-gene silenced">
            <span>Ker</span>
            <span class="gene-status">OFF 🔒</span>
          </div>
          <div class="gene-box mini-gene silenced">
            <span>Neu</span>
            <span class="gene-status">OFF 🔒</span>
          </div>
        </div>
      </div>
    </div>

    
    <div class="takeaway-banner">
      <span class="takeaway-icon">💡</span>
      <div>
        <strong>Key Rule:</strong> Cells keep <em>all</em> DNA. Differentiation switches specific genes <strong>ON</strong> or <strong>OFF</strong>.
      </div>
    </div>
  </div>

  <script>
    function setFocus(mode) {
      const btnAll = document.getElementById('btnAll');
      const btnRBC = document.getElementById('btnRBC');
      const btnMuscle = document.getElementById('btnMuscle');
      const cardRBC = document.getElementById('cardRBC');
      const cardMuscle = document.getElementById('cardMuscle');

      btnAll.classList.remove('active');
      btnRBC.classList.remove('active');
      btnMuscle.classList.remove('active');

      if (mode === 'all') {
        btnAll.classList.add('active');
        cardRBC.style.opacity = '1';
        cardMuscle.style.opacity = '1';
        cardRBC.style.transform = 'none';
        cardMuscle.style.transform = 'none';
      } else if (mode === 'rbc') {
        btnRBC.classList.add('active');
        cardRBC.style.opacity = '1';
        cardMuscle.style.opacity = '0.35';
        cardRBC.style.transform = 'scale(1.02)';
        cardMuscle.style.transform = 'none';
      } else if (mode === 'muscle') {
        btnMuscle.classList.add('active');
        cardRBC.style.opacity = '0.35';
        cardMuscle.style.opacity = '1';
        cardMuscle.style.transform = 'scale(1.02)';
        cardRBC.style.transform = 'none';
      }
    }
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <title>Cell Differentiation</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8fafc;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      padding: 12px;
      min-height: 100%;
      user-select: none;
    }

    .stem-node {
      background: #ffffff;
      border: 2px solid #cbd5e1;
      border-radius: 50px;
      padding: 6px 16px;
      display: flex;
      align-items: center;
      gap: 8px;
      font-size: 13px;
      font-weight: 700;
      box-shadow: 0 2px 6px rgba(0,0,0,0.05);
      z-index: 10;
      cursor: pointer;
      transition: all 0.3s ease;
    }
    .stem-node:hover { border-color: #94a3b8; }
    .stem-node.active { border-color: #64748b; background: #f1f5f9; }

    .stem-icon {
      width: 22px;
      height: 22px;
      border-radius: 50%;
      background: radial-gradient(circle at 35% 35%, #e2e8f0 0%, #94a3b8 80%);
      position: relative;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .stem-nucleus {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      background: #6366f1;
      box-shadow: 0 0 6px #6366f1;
      animation: pulseGlow 2.5s infinite ease-in-out;
    }

    @keyframes pulseGlow {
      0%, 100% { transform: scale(0.9); opacity: 0.8; box-shadow: 0 0 4px #6366f1; }
      50% { transform: scale(1.15); opacity: 1; box-shadow: 0 0 10px #818cf8; }
    }

    .svg-canvas {
      width: 100%;
      max-width: 580px;
      height: 60px;
      overflow: visible;
    }

    .branch-path {
      fill: none;
      stroke: #cbd5e1;
      stroke-width: 2.5;
      stroke-dasharray: 4 4;
      transition: stroke 0.3s ease, stroke-width 0.3s ease;
    }
    .branch-path.active-blue { stroke: #2563eb; stroke-width: 3.5; stroke-dasharray: none; }
    .branch-path.active-red { stroke: #dc2626; stroke-width: 3.5; stroke-dasharray: none; }
    .branch-path.active-green { stroke: #16a34a; stroke-width: 3.5; stroke-dasharray: none; }

    .cards-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 8px;
      width: 100%;
      max-width: 580px;
    }

    .cell-card {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      gap: 6px;
      cursor: pointer;
      transition: border-color 0.3s ease, box-shadow 0.3s ease, background 0.3s ease;
      position: relative;
    }

    .cell-card:hover { border-color: #cbd5e1; }
    .cell-card.active-0 { border-color: #2563eb; box-shadow: 0 4px 12px rgba(37,99,235,0.15); background: #f8faff; }
    .cell-card.active-1 { border-color: #dc2626; box-shadow: 0 4px 12px rgba(220,38,38,0.15); background: #fff8f8; }
    .cell-card.active-2 { border-color: #16a34a; box-shadow: 0 4px 12px rgba(22,163,74,0.15); background: #f8fdf9; }

    .cell-visual {
      width: 54px;
      height: 54px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .card-title {
      font-size: 13px;
      font-weight: 700;
      line-height: 1.2;
    }
    .card-sub {
      font-size: 11px;
      color: #64748b;
      font-weight: 600;
    }

    /* Mini DNA Bar */
    .dna-container {
      width: 100%;
      background: #f1f5f9;
      border-radius: 6px;
      padding: 4px 6px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 4px;
      margin-top: 2px;
    }
    .dna-label {
      font-size: 9px;
      font-weight: 700;
      color: #64748b;
      letter-spacing: 0.5px;
    }
    .gene-bars {
      display: flex;
      gap: 3px;
      align-items: center;
    }
    .gene-band {
      width: 5px;
      height: 12px;
      border-radius: 2px;
      background: #cbd5e1;
      transition: background 0.3s ease, box-shadow 0.3s ease;
    }
    .gene-band.on-blue { background: #2563eb; box-shadow: 0 0 5px #2563eb; }
    .gene-band.on-red { background: #dc2626; box-shadow: 0 0 5px #dc2626; }
    .gene-band.on-green { background: #16a34a; box-shadow: 0 0 5px #16a34a; }

    /* Controls / Stepper */
    .stepper {
      display: flex;
      align-items: center;
      gap: 8px;
      margin-top: 8px;
    }
    .step-btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 4px 10px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      transition: background 0.2s, border-color 0.2s;
    }
    .step-btn:hover { background: #f1f5f9; border-color: #94a3b8; }
    .step-dots {
      display: flex;
      gap: 6px;
    }
    .dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: #cbd5e1;
      cursor: pointer;
      transition: background 0.3s ease;
    }
    .dot.active { background: #2563eb; }

    @media (max-width: 400px) {
      .card-title { font-size: 12px; }
      .card-sub { font-size: 10px; }
      .cell-visual { width: 44px; height: 44px; }
      .dna-container { padding: 3px 4px; }
    }
  </style>
</head>
<body>

  
  <div class="stem-node" id="stemNode" onclick="selectType(3)">
    <div class="stem-icon">
      <div class="stem-nucleus"></div>
    </div>
    <span>Unspecialized Stem Cell</span>
  </div>

  
  <svg class="svg-canvas" viewBox="0 0 300 60" preserveAspectRatio="none">
    <path id="path0" class="branch-path" d="M 150 0 C 150 30, 50 20, 50 60" />
    <path id="path1" class="branch-path" d="M 150 0 C 150 30, 150 30, 150 60" />
    <path id="path2" class="branch-path" d="M 150 0 C 150 30, 250 20, 250 60" />
  </svg>

  
  <div class="cards-grid">
    
    <div class="cell-card" id="card0" onclick="selectType(0)">
      <div class="cell-visual">
        <svg viewBox="0 0 60 60" width="100%" height="100%">
          
          <path d="M 30 25 L 8 10 M 30 25 L 12 32 M 30 25 L 20 4 M 30 25 L 42 12 M 30 25 L 30 48 M 30 48 L 22 56 M 30 48 L 38 56" stroke="#2563eb" stroke-width="2.2" stroke-linecap="round" fill="none"/>
          
          <circle cx="30" cy="25" r="7" fill="#bfdbfe" stroke="#2563eb" stroke-width="1.8"/>
          
          <circle cx="30" cy="25" r="3" fill="#1e3a8a"/>
          
          <circle cx="30" cy="48" r="2.5" fill="#60a5fa"/>
        </svg>
      </div>
      <div>
        <div class="card-title" style="color: #1d4ed8;">Nerve Cell</div>
        <div class="card-sub">Electrical Signaling</div>
      </div>
      <div class="dna-container">
        <span class="dna-label">ACTIVE GENES</span>
        <div class="gene-bars">
          <div class="gene-band on-blue"></div>
          <div class="gene-band"></div>
          <div class="gene-band"></div>
        </div>
      </div>
    </div>

    
    <div class="cell-card" id="card1" onclick="selectType(1)">
      <div class="cell-visual">
        <svg viewBox="0 0 60 60" width="100%" height="100%">
          
          <ellipse cx="30" cy="30" rx="22" ry="16" fill="#ef4444" stroke="#b91c1c" stroke-width="1.8"/>
          <ellipse cx="30" cy="30" rx="12" ry="7" fill="#dc2626" opacity="0.65"/>
          
          <text x="30" y="33" fill="#ffffff" font-size="9" font-weight="bold" text-anchor="middle" font-family="sans-serif">O₂</text>
        </svg>
      </div>
      <div>
        <div class="card-title" style="color: #b91c1c;">Red Blood Cell</div>
        <div class="card-sub">Oxygen Transport</div>
      </div>
      <div class="dna-container">
        <span class="dna-label">ACTIVE GENES</span>
        <div class="gene-bars">
          <div class="gene-band"></div>
          <div class="gene-band on-red"></div>
          <div class="gene-band"></div>
        </div>
      </div>
    </div>

    
    <div class="cell-card" id="card2" onclick="selectType(2)">
      <div class="cell-visual">
        <svg viewBox="0 0 60 60" width="100%" height="100%">
          
          <rect x="8" y="16" width="44" height="28" rx="6" fill="#bbf7d0" stroke="#15803d" stroke-width="1.8"/>
          
          <line x1="16" y1="17" x2="16" y2="43" stroke="#16a34a" stroke-width="1.5" stroke-dasharray="2 2"/>
          <line x1="24" y1="17" x2="24" y2="43" stroke="#16a34a" stroke-width="1.5" stroke-dasharray="2 2"/>
          <line x1="32" y1="17" x2="32" y2="43" stroke="#16a34a" stroke-width="1.5" stroke-dasharray="2 2"/>
          <line x1="40" y1="17" x2="40" y2="43" stroke="#16a34a" stroke-width="1.5" stroke-dasharray="2 2"/>
          
          <ellipse cx="20" cy="22" rx="3.5" ry="2" fill="#14532d"/>
          <ellipse cx="36" cy="38" rx="3.5" ry="2" fill="#14532d"/>
        </svg>
      </div>
      <div>
        <div class="card-title" style="color: #15803d;">Muscle Cell</div>
        <div class="card-sub">Contraction</div>
      </div>
      <div class="dna-container">
        <span class="dna-label">ACTIVE GENES</span>
        <div class="gene-bars">
          <div class="gene-band"></div>
          <div class="gene-band"></div>
          <div class="gene-band on-green"></div>
        </div>
      </div>
    </div>
  </div>

  
  <div class="stepper">
    <button class="step-btn" id="playBtn" onclick="togglePlay()">⏸ Pause</button>
    <div class="step-dots">
      <div class="dot" onclick="selectType(0)"></div>
      <div class="dot" onclick="selectType(1)"></div>
      <div class="dot" onclick="selectType(2)"></div>
      <div class="dot" onclick="selectType(3)"></div>
    </div>
  </div>

  <script>
    let currentIndex = 0;
    let isPlaying = true;
    let timer = null;

    const paths = [document.getElementById('path0'), document.getElementById('path1'), document.getElementById('path2')];
    const cards = [document.getElementById('card0'), document.getElementById('card1'), document.getElementById('card2')];
    const stemNode = document.getElementById('stemNode');
    const dots = document.querySelectorAll('.dot');
    const playBtn = document.getElementById('playBtn');

    const activeClasses = ['active-blue', 'active-red', 'active-green'];

    function renderState(idx) {
      currentIndex = idx;

      // Reset all pathways
      paths.forEach((p, i) => {
        p.className.baseVal = 'branch-path';
      });

      // Reset all cards
      cards.forEach((c, i) => {
        c.className = 'cell-card';
      });

      // Reset stem
      stemNode.classList.remove('active');

      // Reset dots
      dots.forEach((d, i) => {
        d.classList.toggle('active', i === idx);
      });

      if (idx >= 0 && idx <= 2) {
        paths[idx].className.baseVal = 'branch-path ' + activeClasses[idx];
        cards[idx].classList.add('active-' + idx);
      } else {
        // Stem cell overview state
        stemNode.classList.add('active');
        paths.forEach((p, i) => {
          p.className.baseVal = 'branch-path ' + activeClasses[i];
        });
      }
    }

    function selectType(idx) {
      renderState(idx);
    }

    function nextStep() {
      const next = (currentIndex + 1) % 4;
      renderState(next);
    }

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

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

    // Init
    renderState(0);
    startTimer();
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <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;
    }

    .nav-bar {
      display: flex;
      gap: 6px;
      margin-bottom: 8px;
      justify-content: center;
    }

    .nav-btn {
      flex: 1;
      max-width: 130px;
      padding: 6px 4px;
      font-size: 12px;
      font-weight: 600;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #334155;
      border-radius: 6px;
      cursor: pointer;
      text-align: center;
      transition: background 0.15s, color 0.15s, border-color 0.15s;
    }

    .nav-btn.active {
      background: #1e40af;
      color: #ffffff;
      border-color: #1e40af;
      box-shadow: 0 1px 3px rgba(30, 64, 175, 0.3);
    }

    .grid-container {
      display: grid;
      grid-template-columns: 1fr;
      gap: 8px;
    }

    @media (min-width: 580px) {
      .nav-bar { display: none; }
      .grid-container {
        grid-template-columns: repeat(3, 1fr);
      }
      .cell-card {
        display: flex !important;
      }
    }

    .cell-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 8px 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }

    .cell-card.hidden {
      display: none;
    }

    .card-title {
      font-size: 13px;
      font-weight: 700;
      color: #0f172a;
      margin-bottom: 2px;
      text-align: center;
    }

    .svg-box {
      width: 100%;
      height: 165px;
      display: flex;
      justify-content: center;
      align-items: center;
    }

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

    .label-text {
      font-size: 10.5px;
      font-weight: 700;
      fill: #0f172a;
    }

    .sub-label {
      font-size: 9px;
      font-weight: 600;
      fill: #1e40af;
    }

    .leader-line {
      stroke: #64748b;
      stroke-width: 1.2;
      stroke-dasharray: 2, 2;
    }

    .target-dot {
      fill: #1e40af;
    }

    /* Pulse animation for nerve signal */
    @keyframes pulseSignal {
      0% { cx: 48; opacity: 0; }
      20% { opacity: 1; }
      80% { opacity: 1; }
      100% { cx: 168; opacity: 0; }
    }

    .signal-dot {
      animation: pulseSignal 2.4s ease-in-out infinite;
    }
  </style>
</head>
<body>

  
  <div class="nav-bar">
    <button class="nav-btn active" onclick="showCell(0)">Sperm Cell</button>
    <button class="nav-btn" onclick="showCell(1)">Red Blood Cell</button>
    <button class="nav-btn" onclick="showCell(2)">Nerve Cell</button>
  </div>

  <div class="grid-container">
    
    <div class="cell-card" id="card-0">
      <div class="card-title">Sperm Cell</div>
      <div class="svg-box">
        <svg viewBox="0 0 200 160" aria-label="Sperm Cell Diagram">
          
          <line x1="32" y1="26" x2="48" y2="48" class="leader-line" />
          <circle cx="48" cy="48" r="2.5" class="target-dot" />
          <text x="32" y="13" text-anchor="middle" class="label-text">Acrosome</text>
          <text x="32" y="24" text-anchor="middle" class="sub-label">Enzymes</text>

          
          <line x1="145" y1="26" x2="86" y2="68" class="leader-line" />
          <circle cx="86" cy="68" r="2.5" class="target-dot" />
          <text x="145" y="13" text-anchor="middle" class="label-text">Mitochondria</text>
          <text x="145" y="24" text-anchor="middle" class="sub-label">ATP for swimming</text>

          
          <line x1="150" y1="126" x2="142" y2="92" class="leader-line" />
          <circle cx="142" cy="92" r="2.5" class="target-dot" />
          <text x="150" y="140" text-anchor="middle" class="label-text">Flagellum</text>
          <text x="150" y="151" text-anchor="middle" class="sub-label">Tail motion</text>

          
          <path d="M 94 75 Q 120 75 140 95 T 185 105" fill="none" stroke="#60a5fa" stroke-width="3.5" stroke-linecap="round" />

          
          <rect x="74" y="66" width="20" height="18" rx="4" fill="#3b82f6" />
          
          <line x1="79" y1="68" x2="79" y2="82" stroke="#93c5fd" stroke-width="2" />
          <line x1="84" y1="68" x2="84" y2="82" stroke="#93c5fd" stroke-width="2" />
          <line x1="89" y1="68" x2="89" y2="82" stroke="#93c5fd" stroke-width="2" />

          
          <ellipse cx="58" cy="75" rx="18" ry="12" fill="#93c5fd" />
          
          <ellipse cx="60" cy="75" rx="9" ry="7" fill="#1e3a8a" />

          
          <path d="M 40 75 Q 40 64 52 64 L 52 86 Q 40 86 40 75 Z" fill="#2563eb" />
        </svg>
      </div>
    </div>

    
    <div class="cell-card hidden" id="card-1">
      <div class="card-title">Red Blood Cell</div>
      <div class="svg-box">
        <svg viewBox="0 0 200 160" aria-label="Red Blood Cell Diagram">
          
          <line x1="50" y1="26" x2="82" y2="58" class="leader-line" />
          <circle cx="82" cy="58" r="2.5" class="target-dot" />
          <text x="50" y="13" text-anchor="middle" class="label-text">Biconcave Disc</text>
          <text x="50" y="24" text-anchor="middle" class="sub-label">High SA : Vol ratio</text>

          
          <line x1="145" y1="126" x2="105" y2="92" class="leader-line" />
          <circle cx="105" cy="92" r="2.5" class="target-dot" />
          <text x="145" y="140" text-anchor="middle" class="label-text">No Nucleus</text>
          <text x="145" y="151" text-anchor="middle" class="sub-label">Max haemoglobin</text>

          
          <ellipse cx="100" cy="82" rx="55" ry="34" fill="#ef4444" />
          <ellipse cx="100" cy="82" rx="34" ry="19" fill="#dc2626" />
          <ellipse cx="100" cy="82" rx="19" ry="10" fill="#b91c1c" />

          
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UK-GCSE-SCIENCE-BIO-CB-02-02

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