<!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>Natural Light Sources</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    html, body {
      width: 100%;
      height: 100%;
      background: #f8fafc;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      justify-content: center;
      padding: 10px;
    }
    .grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      grid-template-rows: 1fr 1fr;
      gap: 10px;
      width: 100%;
      height: 100%;
      max-width: 600px;
      max-height: 440px;
      margin: 0 auto;
    }
    .source-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      text-align: center;
      transition: box-shadow 0.2s ease, border-color 0.2s ease;
      position: relative;
      overflow: hidden;
    }
    .source-card:active,
    .source-card.active {
      border-color: #22b7ff;
      box-shadow: 0 0 0 2px rgba(34, 183, 255, 0.3);
    }
    .visual-box {
      flex: 1;
      width: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      min-height: 60px;
    }
    .info {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 2px;
      width: 100%;
    }
    .title {
      font-size: 15px;
      font-weight: 700;
      color: #1e2945;
      line-height: 1.2;
    }
    .subtitle {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      line-height: 1.2;
    }

    /* 1. Sun Graphic */
    .sun-core {
      width: 44px;
      height: 44px;
      border-radius: 50%;
      background: radial-gradient(circle, #fff7ed 10%, #facc15 50%, #ea580c 100%);
      box-shadow: 0 0 16px #f59e0b, 0 0 32px rgba(245, 158, 11, 0.4);
      animation: sunGlow 3s ease-in-out infinite alternate;
    }
    @keyframes sunGlow {
      0% { box-shadow: 0 0 12px #f59e0b, 0 0 20px rgba(245, 158, 11, 0.3); }
      100% { box-shadow: 0 0 22px #f59e0b, 0 0 40px rgba(245, 158, 11, 0.6); }
    }

    /* 2. Stars Graphic */
    .sky-box {
      width: 100%;
      height: 100%;
      max-height: 72px;
      background: radial-gradient(ellipse at center, #1e1b4b 0%, #0f172a 100%);
      border-radius: 8px;
      position: relative;
      overflow: hidden;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .star {
      position: absolute;
      background: #ffffff;
      border-radius: 50%;
      animation: twinkle 2.5s infinite ease-in-out;
    }
    .star-1 { top: 22%; left: 24%; width: 4px; height: 4px; box-shadow: 0 0 6px #fff; animation-delay: 0s; }
    .star-2 { top: 60%; left: 30%; width: 3px; height: 3px; box-shadow: 0 0 4px #fff; animation-delay: 0.8s; }
    .star-3 { top: 30%; left: 75%; width: 5px; height: 5px; box-shadow: 0 0 8px #93c5fd; animation-delay: 1.4s; }
    .star-4 { top: 68%; left: 70%; width: 3px; height: 3px; box-shadow: 0 0 4px #fff; animation-delay: 0.4s; }
    .star-5 { top: 45%; left: 50%; width: 6px; height: 6px; box-shadow: 0 0 10px #fff; animation-delay: 1.8s; }
    @keyframes twinkle {
      0%, 100% { opacity: 0.25; transform: scale(0.8); }
      50% { opacity: 1; transform: scale(1.25); }
    }

    /* 3. Firefly Graphic */
    .firefly-svg {
      width: 64px;
      height: 64px;
    }
    .abdomen-glow {
      animation: bioGlow 2.4s ease-in-out infinite;
      transform-origin: center;
    }
    @keyframes bioGlow {
      0%, 100% { opacity: 0.3; filter: drop-shadow(0 0 2px #84cc16); }
      50% { opacity: 1; filter: drop-shadow(0 0 10px #a3e635) drop-shadow(0 0 16px #bef264); }
    }

    /* 4. Lightning Graphic */
    .lightning-svg {
      width: 68px;
      height: 68px;
    }
    .bolt-path {
      animation: flash 3s infinite;
    }
    @keyframes flash {
      0%, 82%, 94%, 100% { opacity: 0.15; filter: none; }
      84%, 90% { opacity: 1; filter: drop-shadow(0 0 8px #38bdf8) drop-shadow(0 0 14px #60a5fa); }
    }

    @media (max-width: 380px) {
      .title { font-size: 14px; }
      .subtitle { font-size: 11px; }
      .grid { gap: 6px; }
      .source-card { padding: 6px 8px; }
    }
  </style>
</head>
<body>

  <div class="grid">
    
    <div class="source-card">
      <div class="visual-box">
        <div class="sun-core"></div>
      </div>
      <div class="info">
        <span class="title">The Sun</span>
        <span class="subtitle">Giant glowing star</span>
      </div>
    </div>

    
    <div class="source-card">
      <div class="visual-box">
        <div class="sky-box">
          <div class="star star-1"></div>
          <div class="star star-2"></div>
          <div class="star star-3"></div>
          <div class="star star-4"></div>
          <div class="star star-5"></div>
        </div>
      </div>
      <div class="info">
        <span class="title">Distant Stars</span>
        <span class="subtitle">Twinkling night sky</span>
      </div>
    </div>

    
    <div class="source-card">
      <div class="visual-box">
        <svg class="firefly-svg" viewBox="0 0 100 100">
          
          <ellipse cx="40" cy="42" rx="22" ry="10" transform="rotate(-30 40 42)" fill="#94a3b8" opacity="0.6"/>
          <ellipse cx="60" cy="42" rx="22" ry="10" transform="rotate(30 60 42)" fill="#94a3b8" opacity="0.6"/>
          
          <circle cx="50" cy="28" r="7" fill="#334155"/>
          <ellipse cx="50" cy="44" rx="9" ry="11" fill="#1e293b"/>
          
          <ellipse class="abdomen-glow" cx="50" cy="66" rx="11" ry="15" fill="#bef264"/>
          
          <path d="M 47 22 Q 40 12 36 14" stroke="#475569" stroke-width="2" fill="none" stroke-linecap="round"/>
          <path d="M 53 22 Q 60 12 64 14" stroke="#475569" stroke-width="2" fill="none" stroke-linecap="round"/>
        </svg>
      </div>
      <div class="info">
        <span class="title">Firefly</span>
        <span class="subtitle">Living glow</span>
      </div>
    </div>

    
    <div class="source-card">
      <div class="visual-box">
        <svg class="lightning-svg" viewBox="0 0 100 100">
          
          <path d="M 28 42 A 12 12 0 0 1 48 30 A 16 16 0 0 1 74 34 A 12 12 0 0 1 76 52 L 28 52 Z" fill="#64748b"/>
          
          <polygon class="bolt-path" points="52,44 38,62 48,62 42,84 64,58 54,58" fill="#e0f2fe"/>
        </svg>
      </div>
      <div class="info">
        <span class="title">Lightning</span>
        <span class="subtitle">Electric flash</span>
      </div>
    </div>
  </div>

</body>
</html>

Light Sources: Objects That Give Off Their Own Light

<!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, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #f8f9fa;
      color: #1e2945;
      min-height: 100%;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 12px;
    }

    .grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 10px;
      width: 100%;
      max-width: 520px;
    }

    .source-card {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 14px 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      text-align: center;
      cursor: pointer;
      user-select: none;
      transition: border-color 0.25s ease, box-shadow 0.25s ease, background-color 0.25s ease;
      position: relative;
      min-height: 140px;
    }

    .source-card:active {
      opacity: 0.9;
    }

    .source-card.active {
      border-color: #22b7ff;
      background: #f0f9ff;
      box-shadow: 0 4px 14px rgba(34, 183, 255, 0.18);
    }

    .icon-wrap {
      position: relative;
      width: 54px;
      height: 54px;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-bottom: 6px;
    }

    .glow {
      position: absolute;
      width: 44px;
      height: 44px;
      border-radius: 50%;
      background: radial-gradient(circle, rgba(254, 240, 138, 0.9) 0%, rgba(254, 240, 138, 0) 70%);
      opacity: 0.8;
      transition: transform 0.3s ease, opacity 0.3s ease;
    }

    .source-card.active .glow {
      transform: scale(1.3);
      opacity: 1;
      background: radial-gradient(circle, rgba(186, 230, 253, 0.9) 0%, rgba(186, 230, 253, 0) 70%);
    }

    .icon {
      font-size: 32px;
      position: relative;
      z-index: 1;
    }

    .name {
      font-size: 15px;
      font-weight: 700;
      color: #1e2945;
      margin-bottom: 4px;
    }

    .energy-badge {
      display: inline-flex;
      align-items: center;
      gap: 4px;
      font-size: 13px;
      font-weight: 600;
      color: #0284c7;
      background: #e0f2fe;
      padding: 4px 8px;
      border-radius: 6px;
      opacity: 0.25;
      transition: opacity 0.25s ease, transform 0.25s ease;
      transform: translateY(2px);
    }

    .source-card.active .energy-badge {
      opacity: 1;
      transform: translateY(0);
    }

    .hint {
      margin-top: 10px;
      font-size: 13px;
      color: #64748b;
      font-weight: 500;
      text-align: center;
    }
  </style>
</head>
<body>

  <div class="grid">
    
    <div class="source-card active" onclick="toggleCard(this)">
      <div class="icon-wrap">
        <div class="glow"></div>
        <div class="icon">🔦</div>
      </div>
      <div class="name">Flashlight</div>
      <div class="energy-badge">🔋 Battery</div>
    </div>

    
    <div class="source-card active" onclick="toggleCard(this)">
      <div class="icon-wrap">
        <div class="glow"></div>
        <div class="icon">💡</div>
      </div>
      <div class="name">Desk Lamp</div>
      <div class="energy-badge">🔌 Mains Outlet</div>
    </div>

    
    <div class="source-card active" onclick="toggleCard(this)">
      <div class="icon-wrap">
        <div class="glow"></div>
        <div class="icon">📱</div>
      </div>
      <div class="name">Phone Screen</div>
      <div class="energy-badge">🔋 Battery</div>
    </div>

    
    <div class="source-card active" onclick="toggleCard(this)">
      <div class="icon-wrap">
        <div class="glow"></div>
        <div class="icon">🕯️</div>
      </div>
      <div class="name">Candle</div>
      <div class="energy-badge">🔥 Burning Wax</div>
    </div>
  </div>

  <div class="hint">Tap any light to inspect its energy source</div>

  <script>
    function toggleCard(el) {
      el.classList.toggle('active');
    }
  </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;
    }
    body {
      background-color: #0f172a;
      color: #f8fafc;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      user-select: none;
    }
    .status-bar {
      display: flex;
      flex-wrap: wrap;
      justify-content: center;
      gap: 8px;
      width: 100%;
      max-width: 480px;
      margin-bottom: 6px;
    }
    .badge {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      background: rgba(255, 255, 255, 0.08);
      border: 1px solid rgba(255, 255, 255, 0.15);
      border-radius: 8px;
      padding: 5px 10px;
      font-size: 13px;
      font-weight: 600;
    }
    .tag-source {
      color: #4ade80;
      border-color: rgba(74, 222, 128, 0.4);
      background: rgba(74, 222, 128, 0.12);
    }
    .tag-not-source {
      color: #f87171;
      border-color: rgba(248, 113, 113, 0.4);
      background: rgba(248, 113, 113, 0.12);
    }
    .diagram-area {
      width: 100%;
      max-width: 480px;
      position: relative;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }
    .ray-sun {
      stroke: #fbbf24;
      stroke-width: 3.5;
      stroke-dasharray: 8 6;
      animation: flowSun 1.2s linear infinite;
    }
    .ray-moon {
      stroke: #e2e8f0;
      stroke-width: 3.5;
      stroke-dasharray: 8 6;
      animation: flowMoon 1.2s linear infinite;
    }
    @keyframes flowSun {
      from { stroke-dashoffset: 28; }
      to { stroke-dashoffset: 0; }
    }
    @keyframes flowMoon {
      from { stroke-dashoffset: 28; }
      to { stroke-dashoffset: 0; }
    }
    .glow-sun {
      animation: pulseGlow 2.5s ease-in-out infinite alternate;
    }
    @keyframes pulseGlow {
      from { opacity: 0.4; }
      to { opacity: 0.85; }
    }
    .controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      width: 100%;
      max-width: 480px;
      margin-top: 6px;
    }
    .step-btn {
      background: rgba(255, 255, 255, 0.08);
      color: #94a3b8;
      border: 1px solid rgba(255, 255, 255, 0.15);
      border-radius: 6px;
      padding: 6px 12px;
      font-size: 13px;
      font-weight: 500;
      cursor: pointer;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
    }
    .step-btn.active {
      background: #38bdf8;
      color: #0f172a;
      border-color: #38bdf8;
      font-weight: 700;
    }
    .play-btn {
      background: rgba(255, 255, 255, 0.12);
      color: #f8fafc;
      border: 1px solid rgba(255, 255, 255, 0.2);
      border-radius: 6px;
      padding: 6px 10px;
      font-size: 13px;
      cursor: pointer;
    }
    .label-text {
      fill: #f8fafc;
      font-size: 13px;
      font-weight: 700;
      text-anchor: middle;
      font-family: inherit;
    }
    .sub-text {
      fill: #94a3b8;
      font-size: 11px;
      font-weight: 500;
      text-anchor: middle;
      font-family: inherit;
    }
  </style>
</head>
<body>

  
  <div class="status-bar">
    <div class="badge tag-source">
      <span>☀️ Sun: Makes Light</span>
      <span>✓</span>
    </div>
    <div class="badge tag-not-source">
      <span>🌑 Moon: Bounces Light</span>
      <span>✗</span>
    </div>
  </div>

  
  <div class="diagram-area">
    <svg viewBox="0 0 460 250">
      <defs>
        
        <radialGradient id="sunGlow" cx="50%" cy="50%" r="50%">
          <stop offset="0%" stop-color="#fbbf24" stop-opacity="0.9" />
          <stop offset="60%" stop-color="#f59e0b" stop-opacity="0.3" />
          <stop offset="100%" stop-color="#f59e0b" stop-opacity="0" />
        </radialGradient>
        
        <radialGradient id="sunCore" cx="40%" cy="40%" r="60%">
          <stop offset="0%" stop-color="#fffbeb" />
          <stop offset="35%" stop-color="#fde047" />
          <stop offset="85%" stop-color="#f59e0b" />
          <stop offset="100%" stop-color="#d97706" />
        </radialGradient>
        
        <radialGradient id="moonGrad" cx="35%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#e2e8f0" />
          <stop offset="60%" stop-color="#94a3b8" />
          <stop offset="100%" stop-color="#475569" />
        </radialGradient>
        
        <radialGradient id="earthGrad" cx="40%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#60a5fa" />
          <stop offset="50%" stop-color="#2563eb" />
          <stop offset="100%" stop-color="#1e3a8a" />
        </radialGradient>
        
        <marker id="arrowSun" markerWidth="8" markerHeight="8" refX="5" refY="4" orient="auto">
          <polygon points="0 1, 6 4, 0 7" fill="#fbbf24" />
        </marker>
        <marker id="arrowMoon" markerWidth="8" markerHeight="8" refX="5" refY="4" orient="auto">
          <polygon points="0 1, 6 4, 0 7" fill="#e2e8f0" />
        </marker>
      </defs>

      
      <circle cx="45" cy="30" r="1" fill="#fff" opacity="0.4" />
      <circle cx="160" cy="180" r="1.5" fill="#fff" opacity="0.5" />
      <circle cx="270" cy="35" r="1" fill="#fff" opacity="0.3" />
      <circle cx="340" cy="40" r="1.5" fill="#fff" opacity="0.6" />
      <circle cx="430" cy="110" r="1" fill="#fff" opacity="0.4" />

      
      <g id="step1Group">
        <line x1="88" y1="130" x2="200" y2="78" class="ray-sun" marker-end="url(#arrowSun)" />
      </g>

      
      <g id="step2Group">
        <line x1="230" y1="78" x2="350" y2="152" class="ray-moon" marker-end="url(#arrowMoon)" />
      </g>

      
      <g id="sunElement">
        <circle cx="60" cy="140" r="48" fill="url(#sunGlow)" class="glow-sun" />
        <circle cx="60" cy="140" r="30" fill="url(#sunCore)" />
        <text x="60" y="194" class="label-text">SUN</text>
        <text x="60" y="210" class="sub-text">Light Source</text>
      </g>

      
      <g id="moonElement">
        <circle cx="218" cy="65" r="22" fill="url(#moonGrad)" stroke="#cbd5e1" stroke-width="1" />
        
        <circle cx="212" cy="60" r="3.5" fill="#64748b" opacity="0.6" />
        <circle cx="225" cy="70" r="2.5" fill="#64748b" opacity="0.6" />
        <circle cx="224" cy="58" r="1.8" fill="#64748b" opacity="0.6" />
        <text x="218" y="108" class="label-text">MOON</text>
        <text x="218" y="124" class="sub-text">Reflector</text>
      </g>

      
      <g id="earthElement">
        <circle cx="390" cy="175" r="34" fill="url(#earthGrad)" stroke="#93c5fd" stroke-width="1" />
        
        <path d="M375,160 Q385,155 395,165 Q390,180 380,182 Z" fill="#22c55e" opacity="0.85" />
        <path d="M400,175 Q412,170 415,185 Q405,192 398,185 Z" fill="#22c55e" opacity="0.85" />
        
        
        <circle cx="358" cy="158" r="14" fill="#0f172a" stroke="#38bdf8" stroke-width="1.5" />
        <text x="358" y="163" text-anchor="middle" font-size="15">👁️</text>

        <text x="390" y="226" class="label-text">EARTH</text>
        <text x="390" y="242" class="sub-text">Observer Sees Moon</text>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <button id="btnAll" class="step-btn active">All Flow</button>
    <button id="btnStep1" class="step-btn">1. Sun Emits</button>
    <button id="btnStep2" class="step-btn">2. Moon Bounces</button>
    <button id="playBtn" class="play-btn" aria-label="Toggle Animation">⏸</button>
  </div>

  <script>
    const raySun = document.querySelector('.ray-sun');
    const rayMoon = document.querySelector('.ray-moon');
    const step1Group = document.getElementById('step1Group');
    const step2Group = document.getElementById('step2Group');
    const btnAll = document.getElementById('btnAll');
    const btnStep1 = document.getElementById('btnStep1');
    const btnStep2 = document.getElementById('btnStep2');
    const playBtn = document.getElementById('playBtn');

    let currentMode = 'all';
    let isPlaying = true;
    let autoInterval = null;

    function setMode(mode) {
      currentMode = mode;
      btnAll.classList.toggle('active', mode === 'all');
      btnStep1.classList.toggle('active', mode === 'step1');
      btnStep2.classList.toggle('active', mode === 'step2');

      if (mode === 'all') {
        step1Group.style.opacity = '1';
        step2Group.style.opacity = '1';
      } else if (mode === 'step1') {
        step1Group.style.opacity = '1';
        step2Group.style.opacity = '0.15';
      } else if (mode === 'step2') {
        step1Group.style.opacity = '0.25';
        step2Group.style.opacity = '1';
      }
    }

    btnAll.addEventListener('click', () => { stopAuto(); setMode('all'); });
    btnStep1.addEventListener('click', () => { stopAuto(); setMode('step1'); });
    btnStep2.addEventListener('click', () => { stopAuto(); setMode('step2'); });

    function togglePlay() {
      isPlaying = !isPlaying;
      playBtn.textContent = isPlaying ? '⏸' : '▶';
      if (isPlaying) {
        raySun.style.animationPlayState = 'running';
        rayMoon.style.animationPlayState = 'running';
        startAuto();
      } else {
        raySun.style.animationPlayState = 'paused';
        rayMoon.style.animationPlayState = 'paused';
        stopAuto();
      }
    }

    playBtn.addEventListener('click', togglePlay);

    function startAuto() {
      stopAuto();
      let stepIndex = 0;
      const sequence = ['all', 'step1', 'step2'];
      autoInterval = setInterval(() => {
        stepIndex = (stepIndex + 1) % sequence.length;
        setMode(sequence[stepIndex]);
      }, 3500);
    }

    function stopAuto() {
      if (autoInterval) {
        clearInterval(autoInterval);
        autoInterval = null;
      }
    }

    // Start auto cycle slowly to let learner observe
    startAuto();
  </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; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #f8f9fa;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 12px;
      user-select: none;
      min-height: 100%;
    }

    .controls {
      display: flex;
      align-items: center;
      gap: 10px;
      margin-bottom: 12px;
      z-index: 10;
    }

    .toggle-btn {
      appearance: none;
      border: 2px solid #22b7ff;
      background: #ffffff;
      color: #1e2945;
      padding: 8px 16px;
      border-radius: 24px;
      font-size: 14px;
      font-weight: 700;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 8px;
      transition: background 0.3s ease, border-color 0.3s ease, color 0.3s ease;
    }

    .toggle-btn.on {
      background: #fef08a;
      border-color: #eab308;
      color: #713f12;
    }

    .scene {
      position: relative;
      width: 100%;
      max-width: 440px;
      height: 330px;
      background: #0f172a;
      border-radius: 16px;
      overflow: hidden;
      transition: background 0.5s ease;
    }

    .scene-svg {
      position: absolute;
      inset: 0;
      width: 100%;
      height: 100%;
      pointer-events: none;
    }

    .ambient-glow {
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      width: 380px;
      height: 380px;
      background: radial-gradient(circle, rgba(254, 240, 138, 0.25) 0%, rgba(250, 204, 21, 0.08) 50%, rgba(15, 23, 42, 0) 75%);
      border-radius: 50%;
      opacity: 1;
      transition: opacity 0.5s ease;
      pointer-events: none;
    }

    .scene.is-off .ambient-glow {
      opacity: 0;
    }

    .ray-line {
      stroke: #fde047;
      stroke-width: 3;
      stroke-linecap: round;
      stroke-dasharray: 8 6;
      animation: rayTravel 1.4s linear infinite;
      transition: opacity 0.4s ease;
      opacity: 0.9;
    }

    .scene.is-off .ray-line {
      opacity: 0;
      animation: none;
    }

    @keyframes rayTravel {
      from { stroke-dashoffset: 28; }
      to { stroke-dashoffset: 0; }
    }

    /* Target Objects */
    .target-object {
      position: absolute;
      transform: translate(-50%, -50%);
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
      transition: opacity 0.5s ease, filter 0.5s ease;
      z-index: 4;
    }

    .target-icon {
      font-size: 38px;
      line-height: 1;
      filter: drop-shadow(0 0 10px rgba(253, 224, 71, 0.6));
      transition: filter 0.5s ease, opacity 0.5s ease;
    }

    .target-label {
      font-size: 12px;
      font-weight: 700;
      color: #f8fafc;
      background: rgba(15, 23, 42, 0.7);
      padding: 2px 8px;
      border-radius: 10px;
      letter-spacing: 0.3px;
      transition: opacity 0.5s ease;
    }

    .scene.is-off .target-object {
      opacity: 0.12;
      filter: grayscale(1) brightness(0.2);
    }

    .scene.is-off .target-label {
      opacity: 0.2;
    }

    /* Center Light Source */
    .center-source {
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      display: flex;
      flex-direction: column;
      align-items: center;
      z-index: 6;
      cursor: pointer;
    }

    .bulb-core {
      width: 72px;
      height: 72px;
      border-radius: 50%;
      background: radial-gradient(circle at 35% 35%, #ffffff 0%, #fef08a 40%, #eab308 100%);
      box-shadow: 0 0 35px rgba(250, 204, 21, 0.9), 0 0 70px rgba(250, 204, 21, 0.4);
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 36px;
      transition: background 0.4s ease, box-shadow 0.4s ease, filter 0.4s ease;
    }

    .scene.is-off .bulb-core {
      background: radial-gradient(circle at 35% 35%, #475569 0%, #334155 60%, #1e293b 100%);
      box-shadow: none;
      filter: brightness(0.7);
    }

    .bulb-label {
      margin-top: 6px;
      text-align: center;
      background: rgba(255, 255, 255, 0.92);
      color: #1e2945;
      padding: 3px 8px;
      border-radius: 12px;
      font-size: 11px;
      font-weight: 800;
      white-space: nowrap;
      line-height: 1.2;
      border: 1px solid rgba(234, 179, 8, 0.3);
      transition: opacity 0.4s ease, background 0.4s ease, color 0.4s ease;
    }

    .bulb-sub {
      display: block;
      font-size: 10px;
      font-weight: 600;
      color: #b45309;
    }

    .scene.is-off .bulb-label {
      background: rgba(30, 41, 59, 0.8);
      color: #94a3b8;
      border-color: rgba(148, 163, 184, 0.2);
    }

    .scene.is-off .bulb-sub {
      color: #64748b;
    }
  </style>
</head>
<body>

  <div class="controls">
    <button id="toggleBtn" class="toggle-btn on" aria-label="Toggle Light Source">
      <span id="btnIcon">💡</span>
      <span id="btnText">Light Source: ON</span>
    </button>
  </div>

  <div id="scene" class="scene">
    <div class="ambient-glow"></div>

    <svg class="scene-svg" viewBox="0 0 400 300" preserveAspectRatio="none">
      
      <line class="ray-line" x1="200" y1="150" x2="80" y2="75" />
      
      <line class="ray-line" x1="200" y1="150" x2="320" y2="75" />
      
      <line class="ray-line" x1="200" y1="150" x2="200" y2="250" />
    </svg>

    
    <div class="target-object" style="top: 25%; left: 20%;">
      <div class="target-icon">📖</div>
      <div class="target-label">Book</div>
    </div>

    <div class="target-object" style="top: 25%; left: 80%;">
      <div class="target-icon">🍎</div>
      <div class="target-label">Apple</div>
    </div>

    <div class="target-object" style="top: 83%; left: 50%;">
      <div class="target-icon">🚗</div>
      <div class="target-label">Toy Car</div>
    </div>

    
    <div id="centerSource" class="center-source" title="Click to toggle light">
      <div class="bulb-core">💡</div>
      <div class="bulb-label">
        Light Source
        <span class="bulb-sub">(Makes its own light)</span>
      </div>
    </div>
  </div>

  <script>
    const toggleBtn = document.getElementById('toggleBtn');
    const centerSource = document.getElementById('centerSource');
    const scene = document.getElementById('scene');
    const btnText = document.getElementById('btnText');
    const btnIcon = document.getElementById('btnIcon');

    let isOn = true;

    function toggleLight() {
      isOn = !isOn;
      if (isOn) {
        scene.classList.remove('is-off');
        toggleBtn.classList.add('on');
        btnText.textContent = 'Light Source: ON';
        btnIcon.textContent = '💡';
      } else {
        scene.classList.add('is-off');
        toggleBtn.classList.remove('on');
        btnText.textContent = 'Light Source: OFF';
        btnIcon.textContent = '🌑';
      }
    }

    toggleBtn.addEventListener('click', toggleLight);
    centerSource.addEventListener('click', toggleLight);
  </script>
</body>
</html>

science.ks2.y1.t4.s1

Aligned learning resources

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