<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
      -webkit-tap-highlight-color: transparent;
    }

    body {
      background-color: #f8fafc;
      color: #1e293b;
      padding: 16px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .main-container {
      width: 100%;
      max-width: 620px;
      display: flex;
      flex-direction: column;
      gap: 16px;
    }

    .flow-grid {
      display: grid;
      grid-template-columns: 1fr auto 1fr;
      align-items: center;
      gap: 12px;
    }

    @media (max-width: 480px) {
      .flow-grid {
        grid-template-columns: 1fr;
        gap: 10px;
      }
      .arrow-col {
        transform: rotate(90deg);
        padding: 4px 0;
      }
    }

    .node-card {
      background: #ffffff;
      border-radius: 14px;
      padding: 14px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      border: 2px solid transparent;
      box-shadow: 0 4px 12px rgba(15, 23, 42, 0.05);
      transition: border-color 0.3s ease, box-shadow 0.3s ease;
    }

    .node-cause {
      border-color: #93c5fd;
      background: linear-gradient(180deg, #ffffff 0%, #eff6ff 100%);
    }

    .node-effect {
      border-color: #86efac;
      background: linear-gradient(180deg, #ffffff 0%, #f0fdf4 100%);
    }

    .tag-badge {
      font-size: 11px;
      font-weight: 800;
      letter-spacing: 0.5px;
      text-transform: uppercase;
      padding: 4px 10px;
      border-radius: 20px;
      margin-bottom: 6px;
    }

    .badge-cause {
      background-color: #dbeafe;
      color: #1d4ed8;
    }

    .badge-effect {
      background-color: #dcfce7;
      color: #15803d;
    }

    .card-title {
      font-size: 15px;
      font-weight: 700;
      color: #0f172a;
      line-height: 1.2;
    }

    .card-subtitle {
      font-size: 13px;
      color: #64748b;
      margin-bottom: 12px;
      font-weight: 500;
    }

    /* Interactive controls in Cause card */
    .selector-group {
      display: flex;
      gap: 6px;
      background: #e2e8f0;
      padding: 3px;
      border-radius: 10px;
      width: 100%;
      max-width: 200px;
    }

    .opt-btn {
      flex: 1;
      border: none;
      background: transparent;
      padding: 8px 6px;
      font-size: 13px;
      font-weight: 600;
      border-radius: 8px;
      color: #475569;
      cursor: pointer;
      transition: background 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
    }

    .opt-btn.active {
      background: #2563eb;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(37, 99, 235, 0.3);
    }

    .vis-box {
      height: 90px;
      width: 100%;
      display: flex;
      align-items: flex-end;
      justify-content: center;
      margin-top: 8px;
      position: relative;
    }

    /* Arrow Connector */
    .arrow-col {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 4px;
    }

    .arrow-svg {
      width: 44px;
      height: 24px;
      filter: drop-shadow(0 2px 4px rgba(37, 99, 235, 0.2));
    }

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

    /* Plant Visualization */
    .plant-stage {
      width: 130px;
      height: 90px;
      display: flex;
      align-items: flex-end;
      justify-content: center;
      position: relative;
    }

    .ruler {
      position: absolute;
      left: 10px;
      bottom: 0;
      height: 80px;
      width: 18px;
      border-right: 2px dashed #cbd5e1;
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      font-size: 10px;
      font-weight: 600;
      color: #94a3b8;
      padding-right: 3px;
      text-align: right;
    }

    .plant-stem {
      width: 6px;
      background: #16a34a;
      border-radius: 3px 3px 0 0;
      transition: height 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
      position: relative;
      margin-left: 14px;
    }

    .pot {
      position: absolute;
      bottom: 0;
      width: 38px;
      height: 18px;
      background: #b45309;
      border-radius: 0 0 6px 6px;
      margin-left: 14px;
    }

    .pot::before {
      content: '';
      position: absolute;
      top: -3px;
      left: -3px;
      width: 44px;
      height: 4px;
      background: #92400e;
      border-radius: 2px;
    }

    .leaves {
      position: absolute;
      top: -10px;
      left: 50%;
      transform: translateX(-50%);
      font-size: 18px;
      line-height: 1;
      transition: transform 0.5s ease;
    }

    .height-readout {
      font-size: 14px;
      font-weight: 700;
      color: #15803d;
      margin-top: 6px;
      background: #dcfce7;
      padding: 3px 10px;
      border-radius: 12px;
      transition: all 0.3s ease;
    }

    /* Question Bubble */
    .question-card {
      background: #ffffff;
      border-radius: 12px;
      padding: 10px 16px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 14px;
      font-weight: 600;
      color: #334155;
      box-shadow: 0 2px 6px rgba(15, 23, 42, 0.04);
      border: 1px dashed #cbd5e1;
      text-align: center;
    }

    .q-icon {
      font-size: 16px;
      display: inline-block;
    }
  </style>
</head>
<body>

  <div class="main-container">
    <div class="flow-grid">
      
      
      <div class="node-card node-cause">
        <span class="tag-badge badge-cause">Cause</span>
        <div class="card-title">Independent Variable</div>
        <div class="card-subtitle">What I Change</div>
        
        <div class="selector-group">
          <button id="btn-0" class="opt-btn active" onclick="setDose(0)">0 mL</button>
          <button id="btn-10" class="opt-btn" onclick="setDose(10)">10 mL</button>
        </div>

        <div class="vis-box">
          <div style="font-size: 32px; filter: drop-shadow(0 2px 4px rgba(0,0,0,0.1));" id="fertilizer-emoji">💧</div>
        </div>
        <div style="font-size: 13px; font-weight: 600; color: #1d4ed8; margin-top: 4px;" id="fertilizer-desc">
          Water Only
        </div>
      </div>

      
      <div class="arrow-col">
        <span class="arrow-label">Affects</span>
        <svg class="arrow-svg" viewBox="0 0 44 24" fill="none">
          <path d="M2 12H34M34 12L24 4M34 12L24 20" stroke="#3b82f6" stroke-width="3.5" stroke-linecap="round" stroke-linejoin="round"/>
        </svg>
      </div>

      
      <div class="node-card node-effect">
        <span class="tag-badge badge-effect">Effect</span>
        <div class="card-title">Dependent Variable</div>
        <div class="card-subtitle">What I Measure</div>
        
        <div class="plant-stage">
          <div class="ruler">
            <span>25cm</span>
            <span>15cm</span>
            <span>5cm</span>
          </div>
          <div class="pot"></div>
          <div id="stem" class="plant-stem" style="height: 24px;">
            <div id="leaves" class="leaves">🌱</div>
          </div>
        </div>

        <div id="height-label" class="height-readout">Height: 8 cm</div>
      </div>

    </div>

    
    <div class="question-card">
      <span class="q-icon">💡</span>
      <span><strong>Core Question:</strong> Does fertilizer change plant height?</span>
    </div>
  </div>

  <script>
    function setDose(amount) {
      const btn0 = document.getElementById('btn-0');
      const btn10 = document.getElementById('btn-10');
      const stem = document.getElementById('stem');
      const leaves = document.getElementById('leaves');
      const heightLabel = document.getElementById('height-label');
      const fertEmoji = document.getElementById('fertilizer-emoji');
      const fertDesc = document.getElementById('fertilizer-desc');

      if (amount === 10) {
        btn0.classList.remove('active');
        btn10.classList.add('active');
        stem.style.height = '62px';
        leaves.textContent = '🌿';
        fertEmoji.textContent = '🧪';
        fertDesc.textContent = '10 mL Fertilizer';
        heightLabel.textContent = 'Height: 22 cm';
        heightLabel.style.backgroundColor = '#bbf7d0';
      } else {
        btn10.classList.remove('active');
        btn0.classList.add('active');
        stem.style.height = '24px';
        leaves.textContent = '🌱';
        fertEmoji.textContent = '💧';
        fertDesc.textContent = '0 mL (Water Only)';
        heightLabel.textContent = 'Height: 8 cm';
        heightLabel.style.backgroundColor = '#dcfce7';
      }
    }
  </script>
</body>
</html>

Identifying Variables: Independent, Dependent, and Controlled

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    }

    body {
      background: #ffffff;
      color: #1e293b;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      min-height: 100%;
      user-select: none;
    }

    /* Section Badges */
    .section-badge {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      font-size: 13px;
      font-weight: 700;
      padding: 4px 10px;
      border-radius: 20px;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }

    .badge-iv {
      background: #e0f2fe;
      color: #0369a1;
      border: 1px solid #bae6fd;
    }

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

    .badge-cv {
      background: #f1f5f9;
      color: #475569;
      border: 1px solid #e2e8f0;
    }

    /* Top: Independent Variable Header */
    .iv-header {
      text-align: center;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
    }

    /* Main Experiment Stage */
    .stage {
      display: grid;
      grid-template-columns: 1fr 1fr auto;
      gap: 8px;
      background: #f8fafc;
      border-radius: 12px;
      padding: 12px 8px 8px 8px;
      position: relative;
      align-items: end;
    }

    /* Plant Columns */
    .plant-col {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-end;
      height: 210px;
      position: relative;
    }

    .condition-pill {
      font-size: 13px;
      font-weight: 600;
      background: #ffffff;
      color: #0284c7;
      padding: 4px 8px;
      border-radius: 12px;
      border: 1.5px solid #0284c7;
      margin-bottom: auto;
      white-space: nowrap;
      box-shadow: 0 1px 3px rgba(0,0,0,0.05);
    }

    /* Plant Artwork */
    .plant-art {
      display: flex;
      flex-direction: column;
      align-items: center;
      width: 100%;
      position: relative;
    }

    .stem {
      width: 6px;
      background: #22c55e;
      border-radius: 3px;
      position: relative;
    }

    .stem-a {
      height: 120px;
    }

    .stem-b {
      height: 48px;
    }

    /* Leaves */
    .leaf {
      position: absolute;
      width: 22px;
      height: 12px;
      background: #16a34a;
      border-radius: 14px 0;
    }

    .leaf.left {
      left: -20px;
      transform: rotate(-25deg);
      border-radius: 0 14px;
    }

    .leaf.right {
      right: -20px;
      transform: rotate(25deg);
    }

    .leaf-top {
      top: 0;
      left: -8px;
      width: 22px;
      height: 12px;
      transform: rotate(-90deg);
      border-radius: 14px 14px 0 0;
    }

    /* Flower */
    .flower {
      position: absolute;
      top: -16px;
      left: 50%;
      transform: translateX(-50%);
      font-size: 20px;
      line-height: 1;
    }

    /* Flower Pot */
    .pot {
      width: 64px;
      height: 44px;
      background: #ea580c;
      clip-path: polygon(0 0, 100% 0, 82% 100%, 18% 100%);
      display: flex;
      align-items: center;
      justify-content: center;
      color: #ffffff;
      font-size: 13px;
      font-weight: 700;
      padding-top: 4px;
    }

    .pot-rim {
      width: 72px;
      height: 8px;
      background: #c2410c;
      border-radius: 3px;
      margin-bottom: -1px;
      z-index: 2;
    }

    /* Dependent Variable / Ruler */
    .dv-col {
      display: flex;
      flex-direction: column;
      align-items: center;
      height: 210px;
      padding-left: 4px;
    }

    .ruler-container {
      display: flex;
      align-items: flex-end;
      height: 100%;
      gap: 4px;
      position: relative;
    }

    .ruler {
      width: 28px;
      height: 160px;
      background: #fef08a;
      border: 1.5px solid #ca8a04;
      border-radius: 4px;
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      padding: 4px 2px;
      font-size: 10px;
      font-weight: 700;
      color: #854d0e;
      position: relative;
    }

    .ruler-mark {
      display: flex;
      justify-content: space-between;
      align-items: center;
      width: 100%;
    }

    .ruler-mark::after {
      content: '';
      width: 8px;
      height: 1px;
      background: #ca8a04;
    }

    /* Height Reference Lines */
    .height-line {
      position: absolute;
      left: -190px;
      right: 28px;
      border-top: 1.5px dashed #16a34a;
      pointer-events: none;
    }

    .line-a {
      bottom: 154px;
    }

    .line-b {
      bottom: 82px;
    }

    .height-tag {
      position: absolute;
      right: 32px;
      font-size: 11px;
      font-weight: 700;
      color: #15803d;
      background: #dcfce7;
      padding: 1px 4px;
      border-radius: 4px;
      transform: translateY(-50%);
      white-space: nowrap;
    }

    /* Bottom: Controlled Variables Box */
    .controlled-box {
      border: 1.5px solid #cbd5e1;
      background: #f8fafc;
      border-radius: 10px;
      padding: 8px 10px;
      display: flex;
      flex-direction: column;
      gap: 6px;
    }

    .controlled-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    .controlled-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 6px;
    }

    .cv-item {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 6px;
      padding: 6px 8px;
      font-size: 13px;
      font-weight: 600;
      color: #334155;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    @media (min-width: 500px) {
      .controlled-grid {
        grid-template-columns: repeat(4, 1fr);
      }
    }
  </style>
</head>
<body>

  
  <div class="iv-header">
    <div class="section-badge badge-iv">Independent Variable (Changed)</div>
  </div>

  
  <div class="stage">
    
    
    <div class="plant-col">
      <div class="condition-pill">☀️ 5 hrs sunlight</div>
      <div class="plant-art">
        <div class="stem stem-a">
          <div class="flower">🌸</div>
          <div class="leaf left" style="top: 25px;"></div>
          <div class="leaf right" style="top: 45px;"></div>
          <div class="leaf left" style="top: 65px;"></div>
          <div class="leaf right" style="top: 85px;"></div>
        </div>
        <div class="pot-rim"></div>
        <div class="pot">Plant A</div>
      </div>
    </div>

    
    <div class="plant-col">
      <div class="condition-pill">⛅ 1 hr sunlight</div>
      <div class="plant-art">
        <div class="stem stem-b">
          <div class="leaf left" style="top: 15px;"></div>
          <div class="leaf right" style="top: 28px;"></div>
        </div>
        <div class="pot-rim"></div>
        <div class="pot">Plant B</div>
      </div>
    </div>

    
    <div class="dv-col">
      <div class="section-badge badge-dv" style="margin-bottom: auto;">Dependent (Measured)</div>
      
      <div class="ruler-container">
        
        <div class="height-line line-a">
          <span class="height-tag">20 cm</span>
        </div>
        <div class="height-line line-b">
          <span class="height-tag">8 cm</span>
        </div>

        
        <div class="ruler">
          <div class="ruler-mark">20</div>
          <div class="ruler-mark">15</div>
          <div class="ruler-mark">10</div>
          <div class="ruler-mark">5</div>
          <div class="ruler-mark">0</div>
        </div>
      </div>
    </div>

  </div>

  
  <div class="controlled-box">
    <div class="controlled-header">
      <span class="section-badge badge-cv">🔒 Controlled Variables (Kept Same)</span>
    </div>
    
    <div class="controlled-grid">
      <div class="cv-item">💧 100 mL water</div>
      <div class="cv-item">🌱 Same soil mix</div>
      <div class="cv-item">🪴 6-inch pot</div>
      <div class="cv-item">🌡️ 21°C room temp</div>
    </div>
  </div>

</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Physics Ramp Experiment</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;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 10px;
      max-width: 720px;
      margin: 0 auto;
    }

    /* Variable Badges Bar */
    .header-tags {
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
      justify-content: flex-start;
      align-items: stretch;
    }
    .var-tag {
      font-size: 12px;
      font-weight: 700;
      padding: 6px 10px;
      border-radius: 6px;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      flex: 1 1 auto;
      min-width: 200px;
    }
    .var-indep { background: #e0f2fe; color: #0369a1; border: 1.5px solid #7dd3fc; }
    .var-dep { background: #dcfce7; color: #15803d; border: 1.5px solid #86efac; }
    .dot {
      display: inline-block;
      width: 8px;
      height: 8px;
      border-radius: 50%;
    }
    .dot-blue { background: #0284c7; }
    .dot-green { background: #16a34a; }

    /* Controlled Variables Pill Bar */
    .controlled-bar {
      display: flex;
      flex-wrap: wrap;
      gap: 6px;
      background: #f8fafc;
      border: 1px solid #cbd5e1;
      border-radius: 8px;
      padding: 8px 10px;
      align-items: center;
      font-size: 12px;
      color: #334155;
    }
    .ctrl-label {
      font-weight: 800;
      color: #0f172a;
      margin-right: 4px;
      font-size: 12px;
    }
    .ctrl-item {
      display: inline-flex;
      align-items: center;
      gap: 5px;
      background: #ffffff;
      padding: 3px 8px;
      border-radius: 4px;
      border: 1px solid #cbd5e1;
      font-weight: 600;
      font-size: 12px;
      color: #334155;
    }
    .ctrl-check { color: #16a34a; font-weight: 800; font-size: 12px; }

    /* SVG Tracks Viewport */
    .track-container {
      width: 100%;
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 8px;
      overflow: hidden;
      position: relative;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
    }

    /* Controls */
    .btn-row {
      display: flex;
      justify-content: center;
      gap: 12px;
      margin-top: 2px;
    }
    .btn {
      background: #0284c7;
      color: #ffffff;
      border: none;
      border-radius: 6px;
      padding: 8px 18px;
      font-size: 13px;
      font-weight: 700;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      transition: background-color 0.15s ease, opacity 0.15s ease;
    }
    .btn:hover { background: #0369a1; }
    .btn:active { background: #075985; }
    .btn-reset { background: #475569; }
    .btn-reset:hover { background: #334155; }
    .btn-reset:active { background: #1e293b; }

    @media (max-width: 480px) {
      body { padding: 6px; gap: 8px; }
      .header-tags { gap: 6px; }
      .var-tag { font-size: 11.5px; padding: 5px 8px; min-width: 100%; }
      .controlled-bar { padding: 6px 8px; font-size: 11px; }
      .ctrl-item { font-size: 11px; padding: 2px 6px; }
      .btn { padding: 7px 14px; font-size: 12px; }
    }
  </style>
</head>
<body>

  
  <div class="header-tags">
    <div class="var-tag var-indep"><span class="dot dot-blue"></span> Independent Variable: Ramp Height (cm)</div>
    <div class="var-tag var-dep"><span class="dot dot-green"></span> Dependent Variable: Distance Rolled (cm)</div>
  </div>

  
  <div class="controlled-bar">
    <span class="ctrl-label">Controlled:</span>
    <span class="ctrl-item"><span class="ctrl-check">✓</span> Same toy car</span>
    <span class="ctrl-item"><span class="ctrl-check">✓</span> Same ramp surface</span>
    <span class="ctrl-item"><span class="ctrl-check">✓</span> Released without pushing</span>
    <span class="ctrl-item"><span class="ctrl-check">✓</span> Same flat floor</span>
  </div>

  
  <div class="track-container">
    <svg viewBox="0 0 620 270" id="simSvg">
      <defs>
        
        <pattern id="floorGrid" width="20" height="20" patternUnits="userSpaceOnUse">
          <path d="M 20 0 L 0 0 0 20" fill="none" stroke="#e2e8f0" stroke-width="1"/>
        </pattern>
        
        <g id="carGraphic">
          
          <rect x="-14" y="-9" width="28" height="9" rx="3" fill="#facc15" stroke="#ca8a04" stroke-width="1.2"/>
          <path d="M -8 -9 L -4 -15 L 6 -15 L 10 -9 Z" fill="#fde047" stroke="#ca8a04" stroke-width="1"/>
          
          <path d="M -5 -9.5 L -2.5 -13.5 L 4.5 -13.5 L 7.5 -9.5 Z" fill="#93c5fd" opacity="0.9"/>
          
          <circle cx="-8" cy="0" r="3.2" fill="#1e293b" stroke="#0f172a" stroke-width="1"/>
          <circle cx="-8" cy="0" r="1" fill="#cbd5e1"/>
          <circle cx="8" cy="0" r="3.2" fill="#1e293b" stroke="#0f172a" stroke-width="1"/>
          <circle cx="8" cy="0" r="1" fill="#cbd5e1"/>
        </g>
      </defs>

      
      <rect x="135" y="0" width="485" height="270" fill="url(#floorGrid)" />

      
      <g transform="translate(0, 0)">
        
        <text x="8" y="32" font-size="12" font-weight="800" fill="#475569">LOW</text>

        
        <line x1="135" y1="64" x2="590" y2="64" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="3,3"/>
        
        
        <path d="M 75 64 L 135 64 L 75 52 Z" fill="#e2e8f0" stroke="#94a3b8" stroke-width="1.2"/>
        <line x1="75" y1="52" x2="135" y2="64" stroke="#475569" stroke-width="2.5" stroke-linecap="round"/>
        
        
        <line x1="68" y1="52" x2="68" y2="64" stroke="#0284c7" stroke-width="2"/>
        <line x1="63" y1="52" x2="73" y2="52" stroke="#0284c7" stroke-width="1.5"/>
        <line x1="63" y1="64" x2="73" y2="64" stroke="#0284c7" stroke-width="1.5"/>
        <text x="58" y="61" font-size="12" font-weight="800" fill="#0284c7" text-anchor="end">10 cm</text>

        
        <g id="res1" opacity="0">
          <line x1="135" y1="67" x2="267" y2="67" stroke="#16a34a" stroke-width="2"/>
          <line x1="135" y1="62" x2="135" y2="72" stroke="#16a34a" stroke-width="1.5"/>
          <line x1="267" y1="62" x2="267" y2="72" stroke="#16a34a" stroke-width="1.5"/>
          
          <rect x="237" y="16" width="60" height="20" rx="4" fill="#dcfce7" stroke="#16a34a" stroke-width="1.5"/>
          <text x="267" y="30.5" font-size="12" font-weight="800" fill="#15803d" text-anchor="middle">120 cm</text>
        </g>

        
        <g id="car1" transform="translate(88, 55) rotate(11.3)">
          <use href="#carGraphic"/>
        </g>
      </g>

      
      <g transform="translate(0, 78)">
        
        <text x="8" y="30" font-size="12" font-weight="800" fill="#475569">MED</text>

        
        <line x1="135" y1="64" x2="590" y2="64" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="3,3"/>
        
        
        <path d="M 75 64 L 135 64 L 75 40 Z" fill="#e2e8f0" stroke="#94a3b8" stroke-width="1.2"/>
        <line x1="75" y1="40" x2="135" y2="64" stroke="#475569" stroke-width="2.5" stroke-linecap="round"/>
        
        
        <line x1="68" y1="40" x2="68" y2="64" stroke="#0284c7" stroke-width="2"/>
        <line x1="63" y1="40" x2="73" y2="40" stroke="#0284c7" stroke-width="1.5"/>
        <line x1="63" y1="64" x2="73" y2="64" stroke="#0284c7" stroke-width="1.5"/>
        <text x="58" y="55" font-size="12" font-weight="800" fill="#0284c7" text-anchor="end">20 cm</text>

        
        <g id="res2" opacity="0">
          <line x1="135" y1="67" x2="399" y2="67" stroke="#16a34a" stroke-width="2"/>
          <line x1="135" y1="62" x2="135" y2="72" stroke="#16a34a" stroke-width="1.5"/>
          <line x1="399" y1="62" x2="399" y2="72" stroke="#16a34a" stroke-width="1.5"/>
          
          <rect x="369" y="16" width="60" height="20" rx="4" fill="#dcfce7" stroke="#16a34a" stroke-width="1.5"/>
          <text x="399" y="30.5" font-size="12" font-weight="800" fill="#15803d" text-anchor="middle">240 cm</text>
        </g>

        
        <g id="car2" transform="translate(88, 46) rotate(21.8)">
          <use href="#carGraphic"/>
        </g>
      </g>

      
      <g transform="translate(0, 156)">
        
        <text x="8" y="26" font-size="12" font-weight="800" fill="#475569">HIGH</text>

        
        <line x1="135" y1="64" x2="590" y2="64" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="3,3"/>
        
        
        <path d="M 75 64 L 135 64 L 75 28 Z" fill="#e2e8f0" stroke="#94a3b8" stroke-width="1.2"/>
        <line x1="75" y1="28" x2="135" y2="64" stroke="#475569" stroke-width="2.5" stroke-linecap="round"/>
        
        
        <line x1="68" y1="28" x2="68" y2="64" stroke="#0284c7" stroke-width="2"/>
        <line x1="63" y1="28" x2="73" y2="28" stroke="#0284c7" stroke-width="1.5"/>
        <line x1="63" y1="64" x2="73" y2="64" stroke="#0284c7" stroke-width="1.5"/>
        <text x="58" y="49" font-size="12" font-weight="800" fill="#0284c7" text-anchor="end">30 cm</text>

        
        <g id="res3" opacity="0">
          <line x1="135" y1="67" x2="520" y2="67" stroke="#16a34a" stroke-width="2"/>
          <line x1="135" y1="62" x2="135" y2="72" stroke="#16a34a" stroke-width="1.5"/>
          <line x1="520" y1="62" x2="520" y2="72" stroke="#16a34a" stroke-width="1.5"/>
          
          <rect x="490" y="16" width="60" height="20" rx="4" fill="#dcfce7" stroke="#16a34a" stroke-width="1.5"/>
          <text x="520" y="30.5" font-size="12" font-weight="800" fill="#15803d" text-anchor="middle">350 cm</text>
        </g>

        
        <g id="car3" transform="translate(88, 37) rotate(31.0)">
          <use href="#carGraphic"/>
        </g>
      </g>

      
      <g transform="translate(0, 252)">
        <line x1="135" y1="0" x2="575" y2="0" stroke="#334155" stroke-width="2" />
        
        
        <line x1="135" y1="0" x2="135" y2="-7" stroke="#334155" stroke-width="2" />
        <text x="135" y="-10" font-size="12" font-weight="800" fill="#0f172a" text-anchor="middle">0 cm</text>

        <line x1="190" y1="0" x2="190" y2="-4" stroke="#64748b" stroke-width="1.2" />

        <line x1="245" y1="0" x2="245" y2="-7" stroke="#334155" stroke-width="2" />
        <text x="245" y="-10" font-size="12" font-weight="800" fill="#0f172a" text-anchor="middle">100 cm</text>

        <line x1="300" y1="0" x2="300" y2="-4" stroke="#64748b" stroke-width="1.2" />

        <line x1="355" y1="0" x2="355" y2="-7" stroke="#334155" stroke-width="2" />
        <text x="355" y="-10" font-size="12" font-weight="800" fill="#0f172a" text-anchor="middle">200 cm</text>

        <line x1="410" y1="0" x2="410" y2="-4" stroke="#64748b" stroke-width="1.2" />

        <line x1="465" y1="0" x2="465" y2="-7" stroke="#334155" stroke-width="2" />
        <text x="465" y="-10" font-size="12" font-weight="800" fill="#0f172a" text-anchor="middle">300 cm</text>

        <line x1="520" y1="0" x2="520" y2="-4" stroke="#64748b" stroke-width="1.2" />

        <line x1="575" y1="0" x2="575" y2="-7" stroke="#334155" stroke-width="2" />
        <text x="575" y="-10" font-size="12" font-weight="800" fill="#0f172a" text-anchor="middle">400 cm</text>
      </g>
    </svg>
  </div>

  
  <div class="btn-row">
    <button class="btn" id="rollBtn">▶ Release Cars</button>
    <button class="btn btn-reset" id="resetBtn">↺ Reset</button>
  </div>

  <script>
    const car1 = document.getElementById('car1');
    const car2 = document.getElementById('car2');
    const car3 = document.getElementById('car3');
    const res1 = document.getElementById('res1');
    const res2 = document.getElementById('res2');
    const res3 = document.getElementById('res3');

    let animId = null;
    let startTime = null;

    const initialConfigs = {
      car1: { x: 88, y: 55, rot: 11.3 },
      car2: { x: 88, y: 46, rot: 21.8 },
      car3: { x: 88, y: 37, rot: 31.0 }
    };

    function resetSimulation() {
      if (animId) {
        cancelAnimationFrame(animId);
        animId = null;
      }
      startTime = null;
      car1.setAttribute('transform', `translate(${initialConfigs.car1.x}, ${initialConfigs.car1.y}) rotate(${initialConfigs.car1.rot})`);
      car2.setAttribute('transform', `translate(${initialConfigs.car2.x}, ${initialConfigs.car2.y}) rotate(${initialConfigs.car2.rot})`);
      car3.setAttribute('transform', `translate(${initialConfigs.car3.x}, ${initialConfigs.car3.y}) rotate(${initialConfigs.car3.rot})`);
      res1.setAttribute('opacity', '0');
      res2.setAttribute('opacity', '0');
      res3.setAttribute('opacity', '0');
    }

    function easeInQuad(t) { return t * t; }
    function easeOutQuad(t) { return t * (2 - t); }
    function clamp(val, min, max) { return Math.min(Math.max(val, min), max); }

    function animate(timestamp) {
      if (!startTime) startTime = timestamp;
      const elapsed = (timestamp - startTime) / 1000;

      // === CAR 1 (Low: 10cm -> 120cm rolled, target x = 267) ===
      const tRamp1 = 0.50;
      const tRoll1 = 0.80;
      if (elapsed < tRamp1) {
        const p = easeInQuad(clamp(elapsed / tRamp1, 0, 1));
        const x = 88 + (135 - 88) * p;
        const y = 55 + (64 - 55) * p;
        const rot = 11.3 * (1 - p);
        car1.setAttribute('transform', `translate(${x}, ${y}) rotate(${rot})`);
      } else {
        const p = easeOutQuad(clamp((elapsed - tRamp1) / tRoll1, 0, 1));
        const x = 135 + (267 - 135) * p;
        car1.setAttribute('transform', `translate(${x}, 64) rotate(0)`);
      }
      res1.setAttribute('opacity', elapsed >= (tRamp1 + tRoll1) ? '1' : '0');

      // === CAR 2 (Med: 20cm -> 240cm rolled, target x = 399) ===
      const tRamp2 = 0.42;
      const tRoll2 = 1.10;
      if (elapsed < tRamp2) {
        const p = easeInQuad(clamp(elapsed / tRamp2, 0, 1));
        const x = 88 + (135 - 88) * p;
        const y = 46 + (64 - 46) * p;
        const rot = 21.8 * (1 - p);
        car2.setAttribute('transform', `translate(${x}, ${y}) rotate(${rot})`);
      } else {
        const p = easeOutQuad(clamp((elapsed - tRamp2) / tRoll2, 0, 1));
        const x = 135 + (399 - 135) * p;
        car2.setAttribute('transform', `translate(${x}, 64) rotate(0)`);
      }
      res2.setAttribute('opacity', elapsed >= (tRamp2 + tRoll2) ? '1' : '0');

      // === CAR 3 (High: 30cm -> 350cm rolled, target x = 520) ===
      const tRamp3 = 0.35;
      const tRoll3 = 1.40;
      if (elapsed < tRamp3) {
        const p = easeInQuad(clamp(elapsed / tRamp3, 0, 1));
        const x = 88 + (135 - 88) * p;
        const y = 37 + (64 - 37) * p;
        const rot = 31.0 * (1 - p);
        car3.setAttribute('transform', `translate(${x}, ${y}) rotate(${rot})`);
      } else {
        const p = easeOutQuad(clamp((elapsed - tRamp3) / tRoll3, 0, 1));
        const x = 135 + (520 - 135) * p;
        car3.setAttribute('transform', `translate(${x}, 64) rotate(0)`);
      }
      res3.setAttribute('opacity', elapsed >= (tRamp3 + tRoll3) ? '1' : '0');

      if (elapsed < 1.85) {
        animId = requestAnimationFrame(animate);
      }
    }

    function startSimulation() {
      resetSimulation();
      animId = requestAnimationFrame(animate);
    }

    document.getElementById('rollBtn').addEventListener('click', startSimulation);
    document.getElementById('resetBtn').addEventListener('click', resetSimulation);

    // Initial smooth demonstration
    setTimeout(startSimulation, 400);
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      -webkit-tap-highlight-color: transparent;
    }

    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #f8fafc;
      color: #1e2945;
      padding: 16px 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
      user-select: none;
    }

    .cards-row {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
      width: 100%;
      max-width: 540px;
    }

    .var-card {
      background: #ffffff;
      border-radius: 14px;
      padding: 12px 6px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      cursor: pointer;
      transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
      position: relative;
      border: 2px solid transparent;
      box-shadow: 0 2px 6px rgba(30, 41, 69, 0.06);
    }

    .var-card:hover {
      box-shadow: 0 4px 12px rgba(30, 41, 69, 0.1);
    }

    .var-card:active {
      transform: scale(0.97);
    }

    /* Independent - Blue */
    .card-independent {
      background: #eff6ff;
      border-color: #bfdbfe;
    }
    .card-independent.active {
      border-color: #2563eb;
      box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.2);
    }
    .card-independent .tag {
      background: #2563eb;
      color: #ffffff;
    }

    /* Dependent - Green */
    .card-dependent {
      background: #f0fdf4;
      border-color: #bbf7d0;
    }
    .card-dependent.active {
      border-color: #16a34a;
      box-shadow: 0 0 0 3px rgba(22, 163, 74, 0.2);
    }
    .card-dependent .tag {
      background: #16a34a;
      color: #ffffff;
    }

    /* Controlled - Amber/Gold */
    .card-controlled {
      background: #fffbeb;
      border-color: #fde68a;
    }
    .card-controlled.active {
      border-color: #d97706;
      box-shadow: 0 0 0 3px rgba(217, 119, 6, 0.2);
    }
    .card-controlled .tag {
      background: #d97706;
      color: #ffffff;
    }

    .tag {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      padding: 3px 6px;
      border-radius: 6px;
      margin-bottom: 8px;
    }

    .icon-box {
      font-size: 32px;
      line-height: 1;
      height: 44px;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-bottom: 8px;
      transition: transform 0.3s ease;
    }

    .card-title {
      font-size: 13px;
      font-weight: 800;
      color: #1e2945;
      margin-bottom: 4px;
      line-height: 1.2;
    }

    .card-caption {
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      line-height: 1.3;
    }

    .card-caption b {
      color: #1e2945;
    }

    /* Converging Flow Connector */
    .connector-wrap {
      width: 100%;
      max-width: 540px;
      height: 36px;
      position: relative;
      display: flex;
      justify-content: center;
    }

    .connector-wrap svg {
      width: 100%;
      height: 100%;
    }

    /* Badge */
    .result-badge {
      background: #ffffff;
      border: 2px solid #6366f1;
      border-radius: 999px;
      padding: 8px 18px;
      display: flex;
      align-items: center;
      gap: 8px;
      box-shadow: 0 3px 10px rgba(99, 102, 241, 0.15);
      cursor: pointer;
      transition: transform 0.2s ease, background 0.2s ease, box-shadow 0.2s ease;
    }

    .result-badge:hover {
      box-shadow: 0 5px 14px rgba(99, 102, 241, 0.25);
    }

    .result-badge:active {
      transform: scale(0.97);
    }

    .badge-icon {
      font-size: 18px;
    }

    .badge-text {
      font-size: 14px;
      font-weight: 800;
      color: #1e2945;
      letter-spacing: 0.2px;
    }

    .badge-sub {
      color: #6366f1;
    }

    /* Interactive Icon Animations */
    .anim-twist {
      animation: twist 0.6s ease-in-out;
    }
    @keyframes twist {
      0% { transform: rotate(0deg); }
      30% { transform: rotate(-25deg); }
      70% { transform: rotate(25deg); }
      100% { transform: rotate(0deg); }
    }

    .anim-measure {
      animation: measure 0.6s ease-in-out;
    }
    @keyframes measure {
      0% { transform: translateY(0); }
      50% { transform: translateY(-4px); }
      100% { transform: translateY(0); }
    }

    .anim-lock {
      animation: lock 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
    }
    @keyframes lock {
      0% { transform: scale(1); }
      50% { transform: scale(1.2) rotate(-6deg); }
      100% { transform: scale(1) rotate(0); }
    }

    @media (max-width: 380px) {
      .tag {
        font-size: 9.5px;
        padding: 2px 4px;
      }
      .icon-box {
        font-size: 26px;
        height: 36px;
      }
      .card-title {
        font-size: 12px;
      }
      .card-caption {
        font-size: 11px;
      }
      .badge-text {
        font-size: 12.5px;
      }
    }
  </style>
</head>
<body>

  
  <div class="cards-row">
    
    <div class="var-card card-independent active" id="card1" onclick="focusCard(0)">
      <div class="tag">Change</div>
      <div class="icon-box" id="icon1">🎛️</div>
      <div class="card-title">Independent</div>
      <div class="card-caption">The <b>ONE</b> thing<br>I change</div>
    </div>

    
    <div class="var-card card-dependent active" id="card2" onclick="focusCard(1)">
      <div class="tag">Measure</div>
      <div class="icon-box" id="icon2">📊</div>
      <div class="card-title">Dependent</div>
      <div class="card-caption">The <b>DATA</b><br>I measure</div>
    </div>

    
    <div class="var-card card-controlled active" id="card3" onclick="focusCard(2)">
      <div class="tag">Same</div>
      <div class="icon-box" id="icon3">🔒</div>
      <div class="card-title">Controlled</div>
      <div class="card-caption">Everything<br><b>KEPT SAME</b></div>
    </div>
  </div>

  
  <div class="connector-wrap">
    <svg viewBox="0 0 300 36" fill="none" preserveAspectRatio="none">
      <path d="M 50 2 L 150 26" stroke="#94a3b8" stroke-width="2" stroke-dasharray="3 3" />
      <path d="M 150 2 L 150 26" stroke="#94a3b8" stroke-width="2" stroke-dasharray="3 3" />
      <path d="M 250 2 L 150 26" stroke="#94a3b8" stroke-width="2" stroke-dasharray="3 3" />
      <circle cx="150" cy="27" r="3.5" fill="#6366f1" />
    </svg>
  </div>

  
  <div class="result-badge" id="fairTestBadge" onclick="pulseAll()">
    <span class="badge-icon">⚖️</span>
    <span class="badge-text">Fair Test <span class="badge-sub">= Reliable Data</span></span>
  </div>

  <script>
    function playTone(freq, dur = 0.2) {
      try {
        const ctx = new (window.AudioContext || window.webkitAudioContext)();
        const osc = ctx.createOscillator();
        const gain = ctx.createGain();
        osc.frequency.value = freq;
        osc.connect(gain);
        gain.connect(ctx.destination);
        gain.gain.setValueAtTime(0.12, ctx.currentTime);
        gain.gain.exponentialRampToValueAtTime(0.001, ctx.currentTime + dur);
        osc.start();
        osc.stop(ctx.currentTime + dur);
      } catch (e) {}
    }

    const animClasses = ['anim-twist', 'anim-measure', 'anim-lock'];
    const freqs = [350, 440, 520];

    function focusCard(index) {
      playTone(freqs[index], 0.25);
      const icon = document.getElementById('icon' + (index + 1));
      const anim = animClasses[index];
      
      icon.classList.remove(anim);
      void icon.offsetWidth;
      icon.classList.add(anim);
    }

    function pulseAll() {
      [0, 1, 2].forEach((idx) => {
        setTimeout(() => focusCard(idx), idx * 120);
      });
    }
  </script>
</body>
</html>

OGS.7.SEP.2

Aligned learning resources

Related diagrams