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

    body {
      width: 100%;
      background: #f8fafc;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e293b;
      display: flex;
      justify-content: center;
      align-items: center;
      padding: 8px;
    }

    .diagram-svg {
      width: 100%;
      max-width: 600px;
      height: auto;
      display: block;
      overflow: visible;
    }

    /* Ray animation - gentle, smooth motion */
    .ray-line {
      stroke: #d97706;
      stroke-width: 1.5;
      stroke-dasharray: 6 5;
      animation: rayMove 3s linear infinite;
    }

    @keyframes rayMove {
      from {
        stroke-dashoffset: 22;
      }
      to {
        stroke-dashoffset: 0;
      }
    }

    /* Labels & Typography */
    .panel-title {
      font-size: 13px;
      font-weight: 700;
      fill: #0f172a;
    }

    .dist-label {
      font-size: 11px;
      font-weight: 600;
      fill: #0284c7;
    }

    .shadow-label-huge {
      font-size: 12px;
      font-weight: 700;
      fill: #b91c1c;
    }

    .shadow-label-small {
      font-size: 12px;
      font-weight: 700;
      fill: #15803d;
    }

    .dim-line {
      stroke: #94a3b8;
      stroke-width: 1;
    }

    .dist-line {
      stroke: #0284c7;
      stroke-width: 1.5;
    }
  </style>
</head>
<body>

  <svg class="diagram-svg" viewBox="0 0 520 310" xmlns="http://www.w3.org/2000/svg">
    <defs>
      
      <marker id="arrow-blue" markerWidth="6" markerHeight="6" refX="4" refY="3" orient="auto">
        <path d="M0,1 L5,3 L0,5 Z" fill="#0284c7" />
      </marker>
      <marker id="arrow-blue-rev" markerWidth="6" markerHeight="6" refX="1" refY="3" orient="auto">
        <path d="M5,1 L0,3 L5,5 Z" fill="#0284c7" />
      </marker>
      <marker id="arrow-red" markerWidth="6" markerHeight="6" refX="4" refY="3" orient="auto">
        <path d="M0,1 L5,3 L0,5 Z" fill="#b91c1c" />
      </marker>
      <marker id="arrow-red-rev" markerWidth="6" markerHeight="6" refX="1" refY="3" orient="auto">
        <path d="M5,1 L0,3 L5,5 Z" fill="#b91c1c" />
      </marker>
      <marker id="arrow-green" markerWidth="6" markerHeight="6" refX="4" refY="3" orient="auto">
        <path d="M0,1 L5,3 L0,5 Z" fill="#15803d" />
      </marker>
      <marker id="arrow-green-rev" markerWidth="6" markerHeight="6" refX="1" refY="3" orient="auto">
        <path d="M5,1 L0,3 L5,5 Z" fill="#15803d" />
      </marker>

      
      <g id="bear">
        
        <circle cx="-6" cy="-8" r="3" fill="currentColor" />
        <circle cx="6" cy="-8" r="3" fill="currentColor" />
        
        <ellipse cx="0" cy="4" rx="7.5" ry="8" fill="currentColor" />
        <circle cx="-7" cy="3" r="2.5" fill="currentColor" />
        <circle cx="7" cy="3" r="2.5" fill="currentColor" />
        
        <circle cx="0" cy="-4" r="6.5" fill="currentColor" />
        
        <ellipse cx="-4.5" cy="11" rx="3" ry="2" fill="currentColor" />
        <ellipse cx="4.5" cy="11" rx="3" ry="2" fill="currentColor" />
      </g>
    </defs>

    
    <g>
      
      <text x="12" y="20" class="panel-title">Close to Light</text>

      
      <polygon points="50,75 390,15 390,135" fill="#fef08a" opacity="0.4" />
      
      <polygon points="98,75 390,20 390,130" fill="#cbd5e1" opacity="0.45" />

      
      <line x1="50" y1="75" x2="390" y2="20" class="ray-line" />
      <line x1="50" y1="75" x2="390" y2="130" class="ray-line" />
      <line x1="50" y1="75" x2="98" y2="75" class="ray-line" />

      
      <g transform="translate(14, 65)">
        <rect x="0" y="6" width="24" height="8" rx="2" fill="#64748b" />
        <polygon points="22,5 36,0 36,20 22,15" fill="#475569" />
        <ellipse cx="36" cy="10" rx="2" ry="10" fill="#facc15" />
      </g>

      
      <use href="#bear" x="98" y="75" style="color: #16a34a;" />

      
      <line x1="50" y1="102" x2="98" y2="102" class="dist-line" marker-start="url(#arrow-blue-rev)" marker-end="url(#arrow-blue)" />
      <line x1="50" y1="88" x2="50" y2="108" class="dim-line" />
      <line x1="98" y1="88" x2="98" y2="108" class="dim-line" />
      <text x="74" y="117" text-anchor="middle" class="dist-label">10 cm</text>

      
      <rect x="390" y="14" width="8" height="122" fill="#94a3b8" rx="2" />

      
      <g transform="translate(390, 75) scale(3.8)" style="color: #334155;">
        <use href="#bear" />
      </g>

      
      <line x1="410" y1="20" x2="410" y2="130" stroke="#b91c1c" stroke-width="1.5" marker-start="url(#arrow-red-rev)" marker-end="url(#arrow-red)" />
      <line x1="404" y1="20" x2="416" y2="20" stroke="#b91c1c" stroke-width="1" />
      <line x1="404" y1="130" x2="416" y2="130" stroke="#b91c1c" stroke-width="1" />
      <text x="422" y="71" class="shadow-label-huge">Huge Shadow</text>
      <text x="422" y="86" class="shadow-label-huge">(30 cm)</text>
    </g>

    
    <line x1="12" y1="150" x2="508" y2="150" stroke="#e2e8f0" stroke-width="1.5" stroke-dasharray="6 6" />

    
    <g transform="translate(0, 155)">
      
      <text x="12" y="20" class="panel-title">Far from Light</text>

      
      <polygon points="50,75 390,15 390,135" fill="#fef08a" opacity="0.4" />
      
      <polygon points="230,75 390,56 390,94" fill="#cbd5e1" opacity="0.45" />

      
      <line x1="50" y1="75" x2="390" y2="56" class="ray-line" />
      <line x1="50" y1="75" x2="390" y2="94" class="ray-line" />
      <line x1="50" y1="75" x2="230" y2="75" class="ray-line" />

      
      <g transform="translate(14, 65)">
        <rect x="0" y="6" width="24" height="8" rx="2" fill="#64748b" />
        <polygon points="22,5 36,0 36,20 22,15" fill="#475569" />
        <ellipse cx="36" cy="10" rx="2" ry="10" fill="#facc15" />
      </g>

      
      <use href="#bear" x="230" y="75" style="color: #16a34a;" />

      
      <line x1="50" y1="102" x2="230" y2="102" class="dist-line" marker-start="url(#arrow-blue-rev)" marker-end="url(#arrow-blue)" />
      <line x1="50" y1="88" x2="50" y2="108" class="dim-line" />
      <line x1="230" y1="88" x2="230" y2="108" class="dim-line" />
      <text x="140" y="117" text-anchor="middle" class="dist-label">40 cm</text>

      
      <rect x="390" y="14" width="8" height="122" fill="#94a3b8" rx="2" />

      
      <g transform="translate(390, 75) scale(1.35)" style="color: #334155;">
        <use href="#bear" />
      </g>

      
      <line x1="410" y1="56" x2="410" y2="94" stroke="#15803d" stroke-width="1.5" marker-start="url(#arrow-green-rev)" marker-end="url(#arrow-green)" />
      <line x1="404" y1="56" x2="416" y2="56" stroke="#15803d" stroke-width="1" />
      <line x1="404" y1="94" x2="416" y2="94" stroke="#15803d" stroke-width="1" />
      <text x="422" y="71" class="shadow-label-small">Small Shadow</text>
      <text x="422" y="86" class="shadow-label-small">(10 cm)</text>
    </g>
  </svg>

</body>
</html>

Changing the Size of Shadows

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Shadow Experiment: Distance and Size</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;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      width: 100%;
      max-width: 680px;
      margin: 0 auto;
    }
    .panel {
      display: flex;
      flex-direction: column;
      gap: 6px;
      background: #ffffff;
      border-radius: 8px;
      padding: 8px 10px 10px 10px;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
    }
    .panel-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 13px;
      font-weight: 700;
      color: #0f172a;
      padding: 0 2px;
    }
    .badge {
      padding: 3px 9px;
      border-radius: 6px;
      font-size: 12px;
      font-weight: 700;
      letter-spacing: 0.2px;
    }
    .badge-blue {
      background: #e0f2fe;
      color: #0369a1;
      border: 1px solid #bae6fd;
    }
    .badge-gray {
      background: #f1f5f9;
      color: #334155;
      border: 1px solid #cbd5e1;
    }
    .stage {
      position: relative;
      width: 100%;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 6px;
      overflow: hidden;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
    }
    .summary-card {
      background: #0f172a;
      color: #ffffff;
      border-radius: 8px;
      padding: 10px 14px;
      display: flex;
      justify-content: center;
      align-items: center;
      gap: 12px 16px;
      flex-wrap: wrap;
      font-size: 12.5px;
      font-weight: 600;
      text-align: center;
    }
    .summary-item {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      flex: 1 1 auto;
      min-width: 180px;
    }
    .summary-item .arrow {
      color: #94a3b8;
      font-weight: 800;
    }
    .pill {
      display: inline-block;
      padding: 2px 7px;
      border-radius: 4px;
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.4px;
      white-space: nowrap;
    }
    .pill-orange {
      background: #ea580c;
      color: #ffffff;
    }
    .pill-blue {
      background: #0284c7;
      color: #ffffff;
    }
    .divider {
      color: #334155;
      font-weight: 300;
    }
    @media (max-width: 440px) {
      .divider {
        display: none;
      }
      .panel-header {
        font-size: 12px;
      }
      .summary-card {
        padding: 8px 10px;
        gap: 8px;
      }
      .summary-item {
        font-size: 12px;
        width: 100%;
      }
    }
  </style>
</head>
<body>

  
  <div class="panel">
    <div class="panel-header">
      <span>Test 1: Close to Light</span>
      <span class="badge badge-blue">Distance: 15 cm</span>
    </div>
    <div class="stage">
      <svg viewBox="0 0 440 115" preserveAspectRatio="xMidYMid meet">
        <defs>
          <linearGradient id="beam1" x1="0%" y1="0%" x2="100%" y2="0%">
            <stop offset="0%" stop-color="#fef08a" stop-opacity="0.95" />
            <stop offset="100%" stop-color="#fde047" stop-opacity="0.3" />
          </linearGradient>
        </defs>

        
        <line x1="0" y1="96" x2="440" y2="96" stroke="#94a3b8" stroke-width="2" />

        
        <polygon points="32,55 350,6 350,96" fill="url(#beam1)" />

        
        <g transform="translate(6, 43)">
          <rect x="0" y="8" width="18" height="8" rx="2" fill="#334155" />
          <polygon points="18,4 28,0 28,24 18,20" fill="#1e293b" />
          <line x1="28" y1="0" x2="28" y2="24" stroke="#eab308" stroke-width="2.5" />
        </g>

        
        <line x1="34" y1="105" x2="110" y2="105" stroke="#0369a1" stroke-width="2" />
        <path d="M 34,105 L 39,102 L 39,108 Z M 110,105 L 105,102 L 105,108 Z" fill="#0369a1" />
        <text x="72" y="103" font-size="11" font-weight="800" fill="#0369a1" text-anchor="middle">15 cm</text>

        
        <g transform="translate(100, 56)">
          
          <rect x="6" y="0" width="8" height="7" rx="1.5" fill="#ef4444" />
          <rect x="8" y="2" width="4" height="2" fill="#fef08a" />
          <line x1="10" y1="0" x2="10" y2="-3" stroke="#ef4444" stroke-width="1.5" />
          
          <rect x="3" y="8" width="14" height="16" rx="2" fill="#dc2626" />
          
          <rect x="0" y="9" width="2.5" height="12" rx="1" fill="#991b1b" />
          <rect x="17.5" y="9" width="2.5" height="12" rx="1" fill="#991b1b" />
          
          <rect x="5" y="25" width="3.5" height="15" rx="1" fill="#7f1d1d" />
          <rect x="11.5" y="25" width="3.5" height="15" rx="1" fill="#7f1d1d" />
        </g>

        
        <rect x="350" y="0" width="90" height="96" fill="#e2e8f0" />
        <line x1="350" y1="0" x2="350" y2="96" stroke="#64748b" stroke-width="1.5" />

        
        <g stroke="#475569" stroke-width="1.5">
          <line x1="350" y1="6" x2="358" y2="6" />
          <line x1="350" y1="21" x2="355" y2="21" />
          <line x1="350" y1="36" x2="358" y2="36" />
          <line x1="350" y1="51" x2="355" y2="51" />
          <line x1="350" y1="66" x2="358" y2="66" />
          <line x1="350" y1="81" x2="355" y2="81" />
          <line x1="350" y1="96" x2="358" y2="96" />
        </g>

        
        <rect x="351" y="6" width="16" height="90" rx="3" fill="#0f172a" opacity="0.9" />

        
        <rect x="372" y="39" width="58" height="24" rx="5" fill="#dc2626" />
        <text x="401" y="55" font-size="11" font-weight="800" fill="#ffffff" text-anchor="middle">36 cm</text>
      </svg>
    </div>
  </div>

  
  <div class="panel">
    <div class="panel-header">
      <span>Test 2: Further from Light</span>
      <span class="badge badge-gray">Distance: 45 cm</span>
    </div>
    <div class="stage">
      <svg viewBox="0 0 440 115" preserveAspectRatio="xMidYMid meet">
        <defs>
          <linearGradient id="beam2" x1="0%" y1="0%" x2="100%" y2="0%">
            <stop offset="0%" stop-color="#fef08a" stop-opacity="0.95" />
            <stop offset="100%" stop-color="#fde047" stop-opacity="0.3" />
          </linearGradient>
        </defs>

        
        <line x1="0" y1="96" x2="440" y2="96" stroke="#94a3b8" stroke-width="2" />

        
        <polygon points="32,55 350,38 350,96" fill="url(#beam2)" />

        
        <g transform="translate(6, 43)">
          <rect x="0" y="8" width="18" height="8" rx="2" fill="#334155" />
          <polygon points="18,4 28,0 28,24 18,20" fill="#1e293b" />
          <line x1="28" y1="0" x2="28" y2="24" stroke="#eab308" stroke-width="2.5" />
        </g>

        
        <line x1="34" y1="105" x2="230" y2="105" stroke="#334155" stroke-width="2" />
        <path d="M 34,105 L 39,102 L 39,108 Z M 230,105 L 225,102 L 225,108 Z" fill="#334155" />
        <text x="132" y="103" font-size="11" font-weight="800" fill="#1e293b" text-anchor="middle">45 cm</text>

        
        <g transform="translate(220, 56)">
          
          <rect x="6" y="0" width="8" height="7" rx="1.5" fill="#ef4444" />
          <rect x="8" y="2" width="4" height="2" fill="#fef08a" />
          <line x1="10" y1="0" x2="10" y2="-3" stroke="#ef4444" stroke-width="1.5" />
          
          <rect x="3" y="8" width="14" height="16" rx="2" fill="#dc2626" />
          
          <rect x="0" y="9" width="2.5" height="12" rx="1" fill="#991b1b" />
          <rect x="17.5" y="9" width="2.5" height="12" rx="1" fill="#991b1b" />
          
          <rect x="5" y="25" width="3.5" height="15" rx="1" fill="#7f1d1d" />
          <rect x="11.5" y="25" width="3.5" height="15" rx="1" fill="#7f1d1d" />
        </g>

        
        <rect x="350" y="0" width="90" height="96" fill="#e2e8f0" />
        <line x1="350" y1="0" x2="350" y2="96" stroke="#64748b" stroke-width="1.5" />

        
        <g stroke="#475569" stroke-width="1.5">
          <line x1="350" y1="6" x2="358" y2="6" />
          <line x1="350" y1="21" x2="355" y2="21" />
          <line x1="350" y1="36" x2="358" y2="36" />
          <line x1="350" y1="51" x2="355" y2="51" />
          <line x1="350" y1="66" x2="358" y2="66" />
          <line x1="350" y1="81" x2="355" y2="81" />
          <line x1="350" y1="96" x2="358" y2="96" />
        </g>

        
        <rect x="351" y="58" width="16" height="38" rx="3" fill="#0f172a" opacity="0.9" />

        
        <rect x="372" y="65" width="58" height="24" rx="5" fill="#0284c7" />
        <text x="401" y="81" font-size="11" font-weight="800" fill="#ffffff" text-anchor="middle">15 cm</text>
      </svg>
    </div>
  </div>

  
  <div class="summary-card">
    <div class="summary-item">
      <span class="pill pill-orange">Closer to light</span>
      <span class="arrow">→</span>
      <span>Taller shadow</span>
    </div>
    <span class="divider">|</span>
    <div class="summary-item">
      <span class="pill pill-blue">Further from light</span>
      <span class="arrow">→</span>
      <span>Shorter shadow</span>
    </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">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      height: 100%;
      padding: 10px 12px;
      user-select: none;
    }
    .svg-wrap {
      width: 100%;
      flex: 1;
      min-height: 0;
      position: relative;
    }
    svg {
      width: 100%;
      height: 100%;
      display: block;
      overflow: visible;
    }
    .controls {
      width: 100%;
      max-width: 420px;
      display: flex;
      flex-direction: column;
      gap: 4px;
      padding-top: 4px;
    }
    .slider-row {
      display: flex;
      align-items: center;
      gap: 10px;
    }
    .slider-label {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      white-space: nowrap;
    }
    input[type="range"] {
      flex: 1;
      height: 6px;
      border-radius: 3px;
      background: #e2e8f0;
      outline: none;
      -webkit-appearance: none;
      cursor: pointer;
    }
    input[type="range"]::-webkit-slider-thumb {
      -webkit-appearance: none;
      width: 20px;
      height: 20px;
      border-radius: 50%;
      background: #2563eb;
      border: 2px solid #ffffff;
      box-shadow: 0 1px 4px rgba(0,0,0,0.25);
      cursor: pointer;
    }
    input[type="range"]::-moz-range-thumb {
      width: 20px;
      height: 20px;
      border-radius: 50%;
      background: #2563eb;
      border: 2px solid #ffffff;
      box-shadow: 0 1px 4px rgba(0,0,0,0.25);
      cursor: pointer;
    }
    .tag {
      font-size: 11px;
      font-weight: 700;
      letter-spacing: 0.02em;
    }
  </style>
</head>
<body>

  <div class="svg-wrap">
    <svg id="diagram" viewBox="0 0 460 260">
      <defs>
        
        <filter id="glow" x="-20%" y="-20%" width="140%" height="140%">
          <feGaussianBlur stdDeviation="3" result="blur" />
          <feComposite in="SourceGraphic" in2="blur" operator="over" />
        </filter>
      </defs>

      
      <polygon id="lightCone" fill="rgba(254, 240, 138, 0.28)" />

      
      <polygon id="shadowCone" fill="rgba(15, 23, 42, 0.07)" />

      
      <g id="raysGroup"></g>

      
      <rect x="428" y="16" width="16" height="228" rx="4" fill="#cbd5e1" />
      <rect id="wallShadow" x="425" y="60" width="8" height="140" rx="3" fill="#0f172a" />

      
      <g transform="translate(14, 114)">
        
        <rect x="0" y="8" width="28" height="16" rx="3" fill="#475569" />
        <rect x="5" y="11" width="18" height="3" fill="#334155" />
        
        <polygon points="28,4 46,-2 46,34 28,28" fill="#f59e0b" />
        
        <ellipse cx="46" cy="16" rx="3" ry="18" fill="#fbbf24" filter="url(#glow)" />
        <ellipse cx="46" cy="16" rx="1.5" ry="14" fill="#fef08a" />
      </g>

      
      <g id="opaqueObject">
        <rect id="blockRect" width="22" height="74" rx="4" fill="#2563eb" stroke="#1d4ed8" stroke-width="1.5" />
        
        <rect id="blockBevel" width="5" height="74" rx="2" fill="#3b82f6" opacity="0.6" />
      </g>

      
      
      <text x="36" y="96" text-anchor="middle" class="tag" fill="#b45309" font-size="12">Light source</text>

      
      <text x="145" y="32" text-anchor="middle" class="tag" fill="#d97706" font-size="12">Straight light rays</text>
      <path d="M 145,36 L 145,46" stroke="#d97706" stroke-width="1.2" stroke-linecap="round" marker-end="url(#arrow)" />

      
      <text id="objectLabel" y="52" text-anchor="middle" class="tag" fill="#1d4ed8" font-size="12">Opaque object</text>
      <line id="objectPointer" y1="56" y2="70" stroke="#2563eb" stroke-width="1.2" />

      
      <text x="408" y="240" text-anchor="end" class="tag" fill="#0f172a" font-size="13">Shadow on wall</text>
      <path d="M 412,236 L 424,220" stroke="#0f172a" stroke-width="1.2" stroke-linecap="round" />
    </svg>
  </div>

  <div class="controls">
    <div class="slider-row">
      <span class="slider-label">Closer to light</span>
      <input type="range" id="posSlider" min="110" max="340" value="200" aria-label="Object distance">
      <span class="slider-label">Closer to wall</span>
    </div>
  </div>

  <script>
    const slider = document.getElementById('posSlider');
    const raysGroup = document.getElementById('raysGroup');
    const lightCone = document.getElementById('lightCone');
    const shadowCone = document.getElementById('shadowCone');
    const opaqueObject = document.getElementById('opaqueObject');
    const blockRect = document.getElementById('blockRect');
    const blockBevel = document.getElementById('blockBevel');
    const wallShadow = document.getElementById('wallShadow');
    const objectLabel = document.getElementById('objectLabel');
    const objectPointer = document.getElementById('objectPointer');

    const SRC_X = 60;
    const SRC_Y = 130;
    const WALL_X = 428;
    const BLOCK_H = 74;
    const BLOCK_W = 22;
    const RAY_COUNT = 15;
    const SPREAD_Y_MIN = 24;
    const SPREAD_Y_MAX = 236;

    function update() {
      const objX = parseFloat(slider.value);
      const objTop = SRC_Y - BLOCK_H / 2;
      const objBottom = SRC_Y + BLOCK_H / 2;

      // Update block position
      opaqueObject.setAttribute('transform', `translate(${objX - BLOCK_W/2}, ${objTop})`);
      blockRect.setAttribute('x', 0);
      blockRect.setAttribute('y', 0);
      blockBevel.setAttribute('x', 0);
      blockBevel.setAttribute('y', 0);

      // Update label position
      objectLabel.setAttribute('x', objX);
      objectPointer.setAttribute('x1', objX);
      objectPointer.setAttribute('x2', objX);
      objectPointer.setAttribute('y2', objTop - 4);

      // Tangent slopes to block edges
      const frontX = objX - BLOCK_W / 2;
      const slopeTop = (objTop - SRC_Y) / (frontX - SRC_X);
      const slopeBottom = (objBottom - SRC_Y) / (frontX - SRC_X);

      // Shadow projection on wall
      const wallShadowTop = Math.max(16, Math.min(240, SRC_Y + slopeTop * (WALL_X - SRC_X)));
      const wallShadowBottom = Math.max(16, Math.min(240, SRC_Y + slopeBottom * (WALL_X - SRC_X)));
      const shadowH = wallShadowBottom - wallShadowTop;

      wallShadow.setAttribute('y', wallShadowTop);
      wallShadow.setAttribute('height', shadowH);

      // Light Cone
      lightCone.setAttribute('points', `
        ${SRC_X},${SRC_Y}
        ${WALL_X},${SPREAD_Y_MIN}
        ${WALL_X},${SPREAD_Y_MAX}
      `);

      // Shadow Umbra Cone
      shadowCone.setAttribute('points', `
        ${objX + BLOCK_W/2},${objTop}
        ${WALL_X},${wallShadowTop}
        ${WALL_X},${wallShadowBottom}
        ${objX + BLOCK_W/2},${objBottom}
      `);

      // Draw light rays
      let raysHTML = '';
      for (let i = 0; i < RAY_COUNT; i++) {
        const targetY = SPREAD_Y_MIN + (i / (RAY_COUNT - 1)) * (SPREAD_Y_MAX - SPREAD_Y_MIN);
        const raySlope = (targetY - SRC_Y) / (WALL_X - SRC_X);
        const hitBlock = (raySlope >= slopeTop && raySlope <= slopeBottom);

        if (hitBlock) {
          // Ray hits block front and is stopped
          const hitX = frontX;
          const hitY = SRC_Y + raySlope * (hitX - SRC_X);
          raysHTML += `
            <line x1="${SRC_X}" y1="${SRC_Y}" x2="${hitX}" y2="${hitY}"
                  stroke="#eab308" stroke-width="1.8" stroke-dasharray="4,4" opacity="0.9" />
            <circle cx="${hitX}" cy="${hitY}" r="2" fill="#ef4444" />
          `;
        } else {
          // Ray passes through to wall
          raysHTML += `
            <line x1="${SRC_X}" y1="${SRC_Y}" x2="${WALL_X}" y2="${targetY}"
                  stroke="#eab308" stroke-width="1.8" stroke-dasharray="4,4" opacity="0.95" />
            <circle cx="${WALL_X}" cy="${targetY}" r="2" fill="#facc15" />
          `;
        }
      }
      raysGroup.innerHTML = raysHTML;
    }

    slider.addEventListener('input', update);
    update();
  </script>
</body>
</html>

science.ks2.y1.t4.s5

Aligned learning resources

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