<!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 {
      width: 100%;
      background: transparent;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 8px;
      user-select: none;
      overflow-x: hidden;
    }

    .header-panel {
      width: 100%;
      max-width: 520px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      background: #f1f5f9;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 8px 14px;
      margin-bottom: 8px;
      gap: 8px;
    }

    .counter-wrap {
      display: flex;
      flex-direction: column;
    }

    .counter-title {
      font-size: 11px;
      text-transform: uppercase;
      letter-spacing: 0.05em;
      color: #64748b;
      font-weight: 700;
    }

    .counter-value {
      font-size: 18px;
      font-weight: 800;
      color: #0284c7;
      line-height: 1.2;
    }

    .revolution-badge {
      background: #e0f2fe;
      color: #0369a1;
      padding: 4px 10px;
      border-radius: 20px;
      font-size: 12px;
      font-weight: 700;
      border: 1px solid #bae6fd;
      text-align: right;
    }

    .svg-container {
      width: 100%;
      max-width: 520px;
      position: relative;
      background: #ffffff;
      border-radius: 12px;
      border: 1px solid #e2e8f0;
      overflow: hidden;
    }

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

    .controls {
      width: 100%;
      max-width: 520px;
      display: flex;
      justify-content: center;
      align-items: center;
      gap: 6px;
      margin-top: 8px;
      flex-wrap: wrap;
    }

    .btn {
      background: #f8fafc;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 6px 12px;
      border-radius: 8px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 4px;
      transition: background 0.15s, border-color 0.15s;
    }

    .btn:hover {
      background: #e2e8f0;
    }

    .btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }

    .legend {
      display: flex;
      justify-content: center;
      gap: 16px;
      width: 100%;
      max-width: 520px;
      margin-top: 8px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
    }

    .legend-item {
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .legend-dot {
      width: 10px;
      height: 10px;
      border-radius: 50%;
    }

    @keyframes axialSpin {
      0% { transform: rotate(0deg); }
      100% { transform: rotate(360deg); }
    }

    .earth-spin-pattern {
      animation: axialSpin 1.8s linear infinite;
      transform-origin: 0px 0px;
    }
  </style>
</head>
<body>

  <div class="header-panel">
    <div class="counter-wrap">
      <span class="counter-title">Time Elapsed</span>
      <span id="dayCounter" class="counter-value">0 Days</span>
    </div>
    <div id="statusBadge" class="revolution-badge">
      Start of Orbit
    </div>
  </div>

  <div class="svg-container">
    <svg viewBox="0 0 520 330">
      <defs>
        
        <radialGradient id="sunGlow" cx="50%" cy="50%" r="50%">
          <stop offset="0%" stop-color="#fffbeb"/>
          <stop offset="25%" stop-color="#fde047"/>
          <stop offset="70%" stop-color="#f59e0b"/>
          <stop offset="100%" stop-color="#ea580c" stop-opacity="0"/>
        </radialGradient>

        <radialGradient id="sunCore" cx="40%" cy="35%" r="60%">
          <stop offset="0%" stop-color="#fef08a"/>
          <stop offset="60%" stop-color="#f59e0b"/>
          <stop offset="100%" stop-color="#d97706"/>
        </radialGradient>

        <radialGradient id="earthShading" cx="35%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#38bdf8"/>
          <stop offset="60%" stop-color="#0284c7"/>
          <stop offset="100%" stop-color="#0c4a6e"/>
        </radialGradient>

        
        <marker id="arrow" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1.5 L 8 5 L 0 8.5 z" fill="#0284c7"/>
        </marker>
      </defs>

      
      <rect width="520" height="330" fill="#f8fafc" rx="8"/>

      
      <ellipse cx="260" cy="170" rx="200" ry="105" fill="none" stroke="#94a3b8" stroke-width="2" stroke-dasharray="6,6"/>

      
      <path d="M 458 150 A 200 105 0 0 0 260 65" fill="none" stroke="#0284c7" stroke-width="2.5" marker-end="url(#arrow)"/>
      <path d="M 62 190 A 200 105 0 0 0 260 275" fill="none" stroke="#0284c7" stroke-width="2.5" marker-end="url(#arrow)"/>

      
      <g transform="translate(260, 48)">
        <rect x="-56" y="-12" width="112" height="22" rx="6" fill="#e2e8f0" opacity="0.9"/>
        <text text-anchor="middle" y="3" font-size="11" font-weight="700" fill="#475569">Orbit (Path)</text>
      </g>

      
      
      <circle cx="260" cy="170" r="54" fill="url(#sunGlow)"/>
      
      <circle cx="260" cy="170" r="26" fill="url(#sunCore)" stroke="#fde047" stroke-width="2"/>
      
      
      <g transform="translate(260, 212)">
        <text text-anchor="middle" font-size="12" font-weight="800" fill="#1e2945">Sun (Center)</text>
      </g>

      
      
      <circle cx="460" cy="170" r="4" fill="#cbd5e1"/>
      <text x="466" y="196" font-size="10" font-weight="700" fill="#64748b">0d / 365d</text>

      
      <circle cx="260" cy="65" r="4" fill="#cbd5e1"/>
      <text x="260" y="80" text-anchor="middle" font-size="10" font-weight="700" fill="#64748b">91 Days (¼)</text>

      
      <circle cx="60" cy="170" r="4" fill="#cbd5e1"/>
      <text x="60" y="196" text-anchor="middle" font-size="10" font-weight="700" fill="#64748b">182 Days (½)</text>

      
      <circle cx="260" cy="275" r="4" fill="#cbd5e1"/>
      <text x="260" y="296" text-anchor="middle" font-size="10" font-weight="700" fill="#64748b">273 Days (¾)</text>

      
      <g id="earthGroup" transform="translate(460, 170)">
        
        <line x1="-8" y1="-26" x2="8" y2="26" stroke="#047857" stroke-width="2" stroke-linecap="round"/>
        
        
        <circle cx="0" cy="0" r="16" fill="url(#earthShading)" stroke="#ffffff" stroke-width="1.5"/>

        
        <g clip-path="url(#earthClip)">
          <defs>
            <clipPath id="earthClip">
              <circle cx="0" cy="0" r="15"/>
            </clipPath>
          </defs>
          <g class="earth-spin-pattern">
            
            <path d="M-10,-5 Q-6,-12 0,-8 Q6,-12 10,-6 Q12,2 6,8 Q-2,12 -8,7 Z" fill="#22c55e" opacity="0.85"/>
            <circle cx="-5" cy="-2" r="4" fill="#15803d" opacity="0.6"/>
            <circle cx="6" cy="4" r="5" fill="#15803d" opacity="0.6"/>
            
            <ellipse cx="0" cy="0" rx="9" ry="15" fill="none" stroke="#ffffff" stroke-width="1" opacity="0.4"/>
            <line x1="0" y1="-15" x2="0" y2="15" stroke="#ffffff" stroke-width="1" opacity="0.4"/>
          </g>
        </g>

        
        <text x="0" y="-22" text-anchor="middle" font-size="11" font-weight="800" fill="#1e2945">Earth</text>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <button id="playBtn" class="btn active">⏸ Pause</button>
    <button id="btn0" class="btn">0d (Start)</button>
    <button id="btn91" class="btn">91d (¼)</button>
    <button id="btn182" class="btn">182d (½)</button>
    <button id="btn273" class="btn">273d (¾)</button>
    <button id="btn365" class="btn">365.25d (1 Yr)</button>
  </div>

  <div class="legend">
    <div class="legend-item">
      <div class="legend-dot" style="background:#0284c7;"></div>
      <span>Revolution (365.25 Days)</span>
    </div>
    <div class="legend-item">
      <div class="legend-dot" style="background:#22c55e;"></div>
      <span>Rotation (Daily Spin)</span>
    </div>
  </div>

  <script>
    // Orbital parameters
    const cx = 260;
    const cy = 170;
    const rx = 200;
    const ry = 105;

    let progress = 0; // 0 to 1 along revolution
    let isPlaying = true;
    let lastTime = null;
    const ORBIT_DURATION = 12000; // 12 seconds per full revolution

    const earthGroup = document.getElementById('earthGroup');
    const dayCounter = document.getElementById('dayCounter');
    const statusBadge = document.getElementById('statusBadge');
    const playBtn = document.getElementById('playBtn');

    const stepButtons = [
      { id: 'btn0', target: 0.0 },
      { id: 'btn91', target: 0.25 },
      { id: 'btn182', target: 0.5 },
      { id: 'btn273', target: 0.75 },
      { id: 'btn365', target: 1.0 }
    ];

    function updateEarthPosition(p) {
      // Counter-clockwise angle: starts at 0 rad (right side)
      // Moving counter-clockwise in screen coordinates means decreasing angle in standard math or negative angle
      const angle = -2 * Math.PI * (p % 1.0);
      const x = cx + rx * Math.cos(angle);
      const y = cy + ry * Math.sin(angle);
      earthGroup.setAttribute('transform', `translate(${x.toFixed(2)}, ${y.toFixed(2)})`);

      // Update days
      const days = (p * 365.25).toFixed(p >= 0.999 ? 2 : 0);
      dayCounter.textContent = `${days} Days`;

      // Update badge status
      if (p >= 0.99) {
        statusBadge.textContent = '1 Full Revolution (1 Year)';
      } else if (p >= 0.74 && p <= 0.76) {
        statusBadge.textContent = '¾ Revolution (Autumn)';
      } else if (p >= 0.49 && p <= 0.51) {
        statusBadge.textContent = '½ Revolution (Summer)';
      } else if (p >= 0.24 && p <= 0.26) {
        statusBadge.textContent = '¼ Revolution (Spring)';
      } else if (p < 0.05) {
        statusBadge.textContent = 'Start of Revolution';
      } else {
        statusBadge.textContent = 'Revolving in Orbit';
      }
    }

    function animate(currentTime) {
      if (!lastTime) lastTime = currentTime;
      const dt = currentTime - lastTime;
      lastTime = currentTime;

      if (isPlaying) {
        progress = (progress + dt / ORBIT_DURATION) % 1.0;
        updateEarthPosition(progress);
      }

      requestAnimationFrame(animate);
    }

    requestAnimationFrame(animate);

    // Play/Pause toggle
    playBtn.addEventListener('click', () => {
      isPlaying = !isPlaying;
      playBtn.textContent = isPlaying ? '⏸ Pause' : '▶ Play';
      playBtn.classList.toggle('active', isPlaying);
    });

    // Milestone buttons
    stepButtons.forEach(btnInfo => {
      const el = document.getElementById(btnInfo.id);
      if (el) {
        el.addEventListener('click', () => {
          isPlaying = false;
          playBtn.textContent = '▶ Play';
          playBtn.classList.remove('active');
          progress = btnInfo.target >= 1.0 ? 0.9999 : btnInfo.target;
          updateEarthPosition(btnInfo.target >= 1.0 ? 1.0 : progress);
        });
      }
    });

    // Initialize
    updateEarthPosition(0);
  </script>
</body>
</html>

What Causes Day, Night, and Years

<!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;
      color: #1e2945;
      background: transparent;
      padding: 8px 4px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 12px;
    }

    .columns {
      display: flex;
      gap: 12px;
      width: 100%;
      max-width: 680px;
    }

    @media (max-width: 599px) {
      .columns {
        flex-direction: column;
      }
    }

    .panel {
      flex: 1;
      border-radius: 12px;
      padding: 14px 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      border: 1px solid rgba(0, 0, 0, 0.06);
    }

    .panel-rot {
      background: #f0f9ff;
      border-color: #bae6fd;
    }

    .panel-rev {
      background: #fff7ed;
      border-color: #fed7aa;
    }

    .badge {
      font-size: 11px;
      font-weight: 700;
      letter-spacing: 0.05em;
      padding: 3px 8px;
      border-radius: 20px;
      text-transform: uppercase;
      margin-bottom: 4px;
    }

    .badge-rot {
      background: #e0f2fe;
      color: #0284c7;
    }

    .badge-rev {
      background: #ffedd5;
      color: #ea580c;
    }

    .title {
      font-size: 18px;
      font-weight: 800;
      letter-spacing: 0.02em;
      margin-bottom: 10px;
    }

    .title-rot { color: #0369a1; }
    .title-rev { color: #c2410c; }

    .stage {
      width: 100%;
      height: 140px;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      margin-bottom: 12px;
    }

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

    .facts {
      width: 100%;
      list-style: none;
      display: flex;
      flex-direction: column;
      gap: 6px;
      text-align: left;
      font-size: 13px;
      line-height: 1.35;
    }

    .facts li {
      display: flex;
      align-items: baseline;
      gap: 6px;
    }

    .check-rot { color: #0284c7; font-weight: bold; }
    .check-rev { color: #ea580c; font-weight: bold; }

    .label {
      font-weight: 600;
      color: #1e2945;
    }

    .stat {
      font-weight: 700;
    }
    .stat-rot { color: #0284c7; }
    .stat-rev { color: #ea580c; }

    /* Interactive control */
    .controls {
      display: flex;
      justify-content: center;
      margin-top: 2px;
    }

    .btn-toggle {
      background: #f8fafc;
      border: 1px solid #cbd5e1;
      color: #475569;
      font-size: 12px;
      font-weight: 600;
      padding: 6px 14px;
      border-radius: 20px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      transition: background 0.15s ease, border-color 0.15s ease;
    }

    .btn-toggle:active {
      background: #e2e8f0;
    }

    /* CSS Animations */
    .spin-group {
      transform-origin: 100px 70px;
      animation: earthSpin 4s linear infinite;
    }

    @keyframes earthSpin {
      0% { transform: rotate(-23.5deg); }
      100% { transform: rotate(-23.5deg); }
    }

    .equator-arrow {
      animation: spinArrow 3s ease-in-out infinite alternate;
      transform-origin: 100px 70px;
    }

    @keyframes spinArrow {
      0% { transform: rotate(-23.5deg) scaleX(0.85); opacity: 0.7; }
      100% { transform: rotate(-23.5deg) scaleX(1.1); opacity: 1; }
    }

    /* Revolution orbit */
    .orbit-anim {
      animation: orbitMove 8s linear infinite;
      transform-origin: 100px 70px;
    }

    @keyframes orbitMove {
      from { transform: rotate(0deg); }
      to { transform: rotate(360deg); }
    }

    .paused * {
      animation-play-state: paused !important;
    }
  </style>
</head>
<body>

  <div class="columns" id="diagramCols">
    
    <div class="panel panel-rot">
      <span class="badge badge-rot">INTERNAL AXIS</span>
      <h2 class="title title-rot">ROTATION</h2>
      
      <div class="stage">
        <svg viewBox="0 0 200 140">
          <defs>
            <radialGradient id="earthGradRot" cx="40%" cy="40%" r="60%">
              <stop offset="0%" stop-color="#7dd3fc" />
              <stop offset="60%" stop-color="#0284c7" />
              <stop offset="100%" stop-color="#0369a1" />
            </radialGradient>
            <marker id="rotArrow" markerWidth="6" markerHeight="6" refX="4" refY="3" orient="auto">
              <polygon points="0 0, 6 3, 0 6" fill="#0284c7" />
            </marker>
          </defs>

          
          <g transform="rotate(-23.5 100 70)">
            <line x1="100" y1="12" x2="100" y2="128" stroke="#0284c7" stroke-width="2" stroke-dasharray="4 3" />
            <text x="100" y="8" font-size="9" font-weight="700" fill="#0284c7" text-anchor="middle">N (23.5°)</text>
            <text x="100" y="137" font-size="9" font-weight="700" fill="#0284c7" text-anchor="middle">S</text>
            
            
            <circle cx="100" cy="70" r="38" fill="url(#earthGradRot)" />
            
            
            <path d="M85 55 Q95 50 102 60 Q98 75 88 72 Z" fill="#22c55e" opacity="0.85" />
            <path d="M105 68 Q118 65 120 80 Q110 88 102 82 Z" fill="#22c55e" opacity="0.85" />
            
            
            <path d="M100 32 A38 38 0 0 1 100 108 A38 38 0 0 0 100 32" fill="#0f172a" opacity="0.25" />
          </g>

          
          <path d="M 68 76 C 75 92, 125 92, 132 76" fill="none" stroke="#0284c7" stroke-width="2.5" stroke-linecap="round" marker-end="url(#rotArrow)" class="equator-arrow" />
          <text x="100" y="112" font-size="10" font-weight="700" fill="#0369a1" text-anchor="middle">Counter-Clockwise</text>
        </svg>
      </div>

      <ul class="facts">
        <li><span class="check-rot">✓</span> <span><b class="label">Motion:</b> Spins on internal axis</span></li>
        <li><span class="check-rot">✓</span> <span><b class="label">Time:</b> <span class="stat stat-rot">24 hours</span> (1 Day)</span></li>
        <li><span class="check-rot">✓</span> <span><b class="label">Result:</b> Day & Night</span></li>
        <li><span class="check-rot">✓</span> <span><b class="label">Analogy:</b> Spinning top</span></li>
      </ul>
    </div>

    
    <div class="panel panel-rev">
      <span class="badge badge-rev">ORBITAL PATH</span>
      <h2 class="title title-rev">REVOLUTION</h2>
      
      <div class="stage">
        <svg viewBox="0 0 200 140">
          <defs>
            <radialGradient id="sunGrad" cx="45%" cy="45%" r="55%">
              <stop offset="0%" stop-color="#fef08a" />
              <stop offset="60%" stop-color="#f59e0b" />
              <stop offset="100%" stop-color="#ea580c" />
            </radialGradient>
            <marker id="orbArrow" markerWidth="6" markerHeight="6" refX="4" refY="3" orient="auto">
              <polygon points="0 0, 6 3, 0 6" fill="#ea580c" />
            </marker>
          </defs>

          
          <ellipse cx="100" cy="70" rx="76" ry="42" fill="none" stroke="#fed7aa" stroke-width="1.5" stroke-dasharray="4 3" />
          
          
          <path d="M 100 28 L 94 28" stroke="#ea580c" stroke-width="2" marker-end="url(#orbArrow)" fill="none" />
          <path d="M 100 112 L 106 112" stroke="#ea580c" stroke-width="2" marker-end="url(#orbArrow)" fill="none" />

          
          <circle cx="100" cy="70" r="18" fill="url(#sunGrad)" />
          <circle cx="100" cy="70" r="23" fill="none" stroke="#fde047" stroke-width="1.5" opacity="0.6" />
          <text x="100" y="74" font-size="10" font-weight="800" fill="#7c2d12" text-anchor="middle">SUN</text>

          
          <g class="orbit-anim">
            <g transform="translate(100 70)">
              
              <g transform="translate(76 0)">
                <line x1="-3" y1="-14" x2="3" y2="14" stroke="#0284c7" stroke-width="1.2" stroke-dasharray="2 1" />
                <circle cx="0" cy="0" r="9" fill="#38bdf8" stroke="#0284c7" stroke-width="1.5" />
                
                <path d="M 0 -9 A 9 9 0 0 1 0 9 A 9 9 0 0 0 0 -9" fill="#0f172a" opacity="0.35" />
              </g>
            </g>
          </g>
          
          <text x="100" y="128" font-size="10" font-weight="700" fill="#c2410c" text-anchor="middle">1 Orbit Around Sun</text>
        </svg>
      </div>

      <ul class="facts">
        <li><span class="check-rev">✓</span> <span><b class="label">Motion:</b> Travels around the Sun</span></li>
        <li><span class="check-rev">✓</span> <span><b class="label">Time:</b> <span class="stat stat-rev">365.25 days</span> (1 Year)</span></li>
        <li><span class="check-rev">✓</span> <span><b class="label">Result:</b> Years & Seasons</span></li>
        <li><span class="check-rev">✓</span> <span><b class="label">Analogy:</b> Car on a track</span></li>
      </ul>
    </div>
  </div>

  <div class="controls">
    <button class="btn-toggle" id="toggleBtn" aria-label="Pause or resume animations">
      <span id="btnIcon">⏸</span> <span id="btnText">Pause Animation</span>
    </button>
  </div>

  <script>
    const toggleBtn = document.getElementById('toggleBtn');
    const btnIcon = document.getElementById('btnIcon');
    const btnText = document.getElementById('btnText');
    const cols = document.getElementById('diagramCols');
    let isPlaying = true;

    toggleBtn.addEventListener('click', () => {
      isPlaying = !isPlaying;
      if (isPlaying) {
        cols.classList.remove('paused');
        btnIcon.textContent = '⏸';
        btnText.textContent = 'Pause Animation';
      } else {
        cols.classList.add('paused');
        btnIcon.textContent = '▶';
        btnText.textContent = 'Play Animation';
      }
    });
  </script>
</body>
</html>

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

    .header-status {
      display: flex;
      justify-content: space-between;
      align-items: center;
      width: 100%;
      max-width: 330px;
      margin-bottom: 8px;
    }

    .time-badge {
      font-size: 16px;
      font-weight: 700;
      color: #1e2945;
      background: #f1f5f9;
      padding: 4px 10px;
      border-radius: 8px;
      border: 1px solid #e2e8f0;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .phase-badge {
      font-size: 14px;
      font-weight: 600;
      color: #0284c7;
      background: #e0f2fe;
      padding: 4px 10px;
      border-radius: 8px;
    }

    .scene-container {
      position: relative;
      width: 100%;
      max-width: 330px;
      height: 220px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

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

    .controls-panel {
      width: 100%;
      max-width: 330px;
      display: flex;
      flex-direction: column;
      gap: 10px;
      margin-top: 10px;
    }

    .slider-row {
      display: flex;
      align-items: center;
      gap: 8px;
      width: 100%;
    }

    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(0,0,0,0.2);
      cursor: pointer;
    }

    .preset-buttons {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 6px;
      width: 100%;
    }

    .btn-step {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 6px;
      padding: 6px 2px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      cursor: pointer;
      text-align: center;
      transition: background 0.2s, color 0.2s, border-color 0.2s;
    }

    .btn-step.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
    }
  </style>
</head>
<body>

  <div class="header-status">
    <div class="time-badge" id="timeDisplay">☀️ 12:00 PM</div>
    <div class="phase-badge" id="phaseDisplay">Noon (Day)</div>
  </div>

  <div class="scene-container">
    <svg viewBox="0 0 340 220">
      <defs>
        
        <radialGradient id="sunGlow" cx="0%" cy="50%" r="90%">
          <stop offset="0%" stop-color="#fffbeb"/>
          <stop offset="40%" stop-color="#fde047"/>
          <stop offset="90%" stop-color="#f59e0b" stop-opacity="0.9"/>
          <stop offset="100%" stop-color="#f59e0b" stop-opacity="0"/>
        </radialGradient>
        
        
        <marker id="arrow" viewBox="0 0 6 6" refX="5" refY="3" markerWidth="4" markerHeight="4" orient="auto-start-reverse">
          <path d="M 0 1 L 5 3 L 0 5 z" fill="#f59e0b"/>
        </marker>

        
        <clipPath id="earthClip">
          <circle cx="230" cy="110" r="54"/>
        </clipPath>
      </defs>

      
      <path d="M -20 10 A 100 100 0 0 1 -20 210 Z" fill="url(#sunGlow)"/>
      <circle cx="-10" cy="110" r="50" fill="#f59e0b"/>
      <text x="18" y="114" fill="#78350f" font-size="12" font-weight="700" text-anchor="middle">SUN</text>

      
      <g stroke="#f59e0b" stroke-width="1.5" stroke-dasharray="3,3" opacity="0.85">
        <line x1="50" y1="75" x2="160" y2="75" marker-end="url(#arrow)"/>
        <line x1="50" y1="110" x2="160" y2="110" marker-end="url(#arrow)"/>
        <line x1="50" y1="145" x2="160" y2="145" marker-end="url(#arrow)"/>
      </g>
      <text x="105" y="102" fill="#d97706" font-size="11" font-weight="600" text-anchor="middle">Sunlight</text>

      
      
      <line x1="205" y1="35" x2="255" y2="185" stroke="#94a3b8" stroke-width="2" stroke-dasharray="4,3"/>
      <text x="200" y="30" fill="#64748b" font-size="11" font-weight="600">Axis</text>

      
      <g clip-path="url(#earthClip)">
        <circle cx="230" cy="110" r="54" fill="#38bdf8"/>
        
        <ellipse cx="205" cy="100" rx="16" ry="24" fill="#4ade80" opacity="0.9"/>
        <ellipse cx="220" cy="130" rx="12" ry="16" fill="#4ade80" opacity="0.9"/>
        
        
        <rect x="230" y="40" width="70" height="140" fill="#0f172a"/>
        
        <circle cx="255" cy="80" r="1" fill="#ffffff" opacity="0.8"/>
        <circle cx="270" cy="120" r="1.2" fill="#ffffff" opacity="0.9"/>
        <circle cx="248" cy="140" r="0.8" fill="#ffffff" opacity="0.7"/>
        <circle cx="265" cy="95" r="0.9" fill="#ffffff" opacity="0.8"/>
      </g>

      
      <line x1="230" y1="56" x2="230" y2="164" stroke="#ffffff" stroke-width="1" opacity="0.5"/>

      
      <text x="195" y="114" fill="#0369a1" font-size="12" font-weight="700" text-anchor="middle">DAY</text>
      <text x="265" y="114" fill="#cbd5e1" font-size="12" font-weight="700" text-anchor="middle">NIGHT</text>

      
      <path d="M 205 178 A 30 10 0 0 0 255 178" fill="none" stroke="#2563eb" stroke-width="2" marker-end="url(#arrow)"/>
      <text x="230" y="200" fill="#2563eb" font-size="11" font-weight="600" text-anchor="middle">Rotation (W → E)</text>

      
      
      <g id="observerGroup" transform="rotate(0, 230, 110)">
        
        
        <circle cx="176" cy="110" r="5.5" fill="#ef4444" stroke="#ffffff" stroke-width="1.5"/>
        <rect x="156" y="82" width="40" height="18" rx="4" fill="#ef4444"/>
        <text x="176" y="95" fill="#ffffff" font-size="11" font-weight="700" text-anchor="middle">YOU</text>
        <line x1="176" y1="100" x2="176" y2="105" stroke="#ef4444" stroke-width="1.5"/>
      </g>
    </svg>
  </div>

  <div class="controls-panel">
    <div class="slider-row">
      <span style="font-size:12px; font-weight:600; color:#64748b;">Rotate:</span>
      <input type="range" id="rotSlider" min="0" max="360" value="0" step="1">
    </div>

    <div class="preset-buttons">
      <button class="btn-step active" onclick="setTime(0)">12 PM<br>Noon</button>
      <button class="btn-step" onclick="setTime(90)">6 PM<br>Sunset</button>
      <button class="btn-step" onclick="setTime(180)">12 AM<br>Midnight</button>
      <button class="btn-step" onclick="setTime(270)">6 AM<br>Sunrise</button>
    </div>
  </div>

  <script>
    const slider = document.getElementById('rotSlider');
    const obsGroup = document.getElementById('observerGroup');
    const timeDisplay = document.getElementById('timeDisplay');
    const phaseDisplay = document.getElementById('phaseDisplay');
    const buttons = document.querySelectorAll('.btn-step');

    const phases = [
      { deg: 0, time: "☀️ 12:00 PM", name: "Noon (Direct Sunlight)" },
      { deg: 90, time: "🌅 6:00 PM", name: "Sunset (Entering Night)" },
      { deg: 180, time: "🌙 12:00 AM", name: "Midnight (Facing Away)" },
      { deg: 270, time: "🌄 6:00 AM", name: "Sunrise (Entering Light)" }
    ];

    function updateDiagram(deg) {
      // Rotate observer group around Earth's center (230, 110)
      obsGroup.setAttribute('transform', `rotate(${deg}, 230, 110)`);

      // Determine time calculation (0 deg = 12:00 PM, 90 deg = 6:00 PM, etc.)
      const totalMinutes = ((deg / 360) * 24 * 60 + 12 * 60) % (24 * 60);
      let hours = Math.floor(totalMinutes / 60);
      const minutes = Math.floor(totalMinutes % 60);
      const isPM = hours >= 12;
      const displayHours = hours % 12 === 0 ? 12 : hours % 12;
      const displayMinutes = minutes < 10 ? '0' + minutes : minutes;
      const ampm = isPM ? 'PM' : 'AM';
      
      let icon = "☀️";
      if (deg > 45 && deg < 135) icon = "🌅";
      else if (deg >= 135 && deg <= 225) icon = "🌙";
      else if (deg > 225 && deg < 315) icon = "🌄";

      timeDisplay.textContent = `${icon} ${displayHours}:${displayMinutes} ${ampm}`;

      // Set phase name
      if (deg >= 45 && deg < 135) {
        phaseDisplay.textContent = "Sunset / Dusk";
        phaseDisplay.style.color = "#d97706";
        phaseDisplay.style.background = "#fef3c7";
      } else if (deg >= 135 && deg < 225) {
        phaseDisplay.textContent = "Midnight (Night)";
        phaseDisplay.style.color = "#4338ca";
        phaseDisplay.style.background = "#e0e7ff";
      } else if (deg >= 225 && deg < 315) {
        phaseDisplay.textContent = "Sunrise / Dawn";
        phaseDisplay.style.color = "#ea580c";
        phaseDisplay.style.background = "#ffedd5";
      } else {
        phaseDisplay.textContent = "Noon (Day)";
        phaseDisplay.style.color = "#0284c7";
        phaseDisplay.style.background = "#e0f2fe";
      }

      // Update button active state
      buttons.forEach((btn, index) => {
        const targetDeg = index * 90;
        const diff = Math.abs(deg - targetDeg);
        if (diff < 15 || Math.abs(deg - (targetDeg + 360)) < 15) {
          btn.classList.add('active');
        } else {
          btn.classList.remove('active');
        }
      });
    }

    slider.addEventListener('input', (e) => {
      updateDiagram(parseFloat(e.target.value));
    });

    function setTime(deg) {
      slider.value = deg;
      updateDiagram(deg);
    }
  </script>
</body>
</html>

OGS.8.ESS.1

Aligned learning resources

Related diagrams