<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Wave Properties</title>
  <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 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100vh;
      box-sizing: border-box;
    }
    .diagram-holder {
      width: 100%;
      max-width: 580px;
      display: flex;
      flex-direction: column;
      gap: 16px;
    }
    .panel {
      width: 100%;
      display: flex;
      flex-direction: column;
      gap: 4px;
    }
    .panel-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      padding: 0 4px;
    }
    .panel-title {
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
      letter-spacing: -0.01em;
    }
    .legend-tag {
      font-size: 11px;
      font-weight: 600;
      padding: 2px 8px;
      border-radius: 9999px;
    }
    .tag-teal {
      background: #ccfbf1;
      color: #0f766e;
    }
    .tag-purple {
      background: #f3e8ff;
      color: #6b21a8;
    }
    .svg-wrap {
      width: 100%;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }
    text {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      user-select: none;
    }
  </style>
</head>
<body>

<div class="diagram-holder">

  
  <div class="panel">
    <div class="panel-header">
      <span class="panel-title">Transverse Wave</span>
      <span class="legend-tag tag-purple">Amplitude (A)</span>
    </div>
    
    <div class="svg-wrap">
      <svg viewBox="0 0 540 170" preserveAspectRatio="xMidYMid meet">
        <defs>
          
          <marker id="arrow-teal-right" viewBox="0 0 8 8" refX="6" refY="4" markerWidth="5" markerHeight="5" orient="auto">
            <path d="M 1 1.5 L 6.5 4 L 1 6.5 z" fill="#0d9488" />
          </marker>
          <marker id="arrow-teal-left" viewBox="0 0 8 8" refX="2" refY="4" markerWidth="5" markerHeight="5" orient="auto">
            <path d="M 7 1.5 L 1.5 4 L 7 6.5 z" fill="#0d9488" />
          </marker>

          
          <marker id="arrow-purple-up" viewBox="0 0 8 8" refX="4" refY="2" markerWidth="5" markerHeight="5" orient="auto">
            <path d="M 1.5 7 L 4 1.5 L 6.5 7 z" fill="#7c3aed" />
          </marker>
          <marker id="arrow-purple-down" viewBox="0 0 8 8" refX="4" refY="6" markerWidth="5" markerHeight="5" orient="auto">
            <path d="M 1.5 1 L 4 6.5 L 6.5 1 z" fill="#7c3aed" />
          </marker>
        </defs>

        
        <line x1="20" y1="95" x2="435" y2="95" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="5,4" />
        <text x="442" y="99" font-size="11" fill="#64748b" font-weight="600">Equilibrium</text>

        
        <line x1="120" y1="52" x2="120" y2="20" stroke="#cbd5e1" stroke-width="1.2" stroke-dasharray="3,3" />
        <line x1="360" y1="52" x2="360" y2="20" stroke="#cbd5e1" stroke-width="1.2" stroke-dasharray="3,3" />

        
        <line x1="124" y1="24" x2="356" y2="24" stroke="#0d9488" stroke-width="2" marker-start="url(#arrow-teal-left)" marker-end="url(#arrow-teal-right)" />
        <rect x="180" y="13" width="120" height="22" rx="6" fill="#ffffff" stroke="#99f6e4" stroke-width="1.2" />
        <text x="240" y="29" font-size="12" fill="#0f766e" font-weight="700" text-anchor="middle" dominant-baseline="middle">Wavelength (λ)</text>

        
        <path id="sinePath" fill="none" stroke="#2563eb" stroke-width="3.5" stroke-linecap="round" />

        
        <line x1="360" y1="91" x2="360" y2="57" stroke="#7c3aed" stroke-width="2" marker-start="url(#arrow-purple-down)" marker-end="url(#arrow-purple-up)" />
        <rect x="372" y="63" width="102" height="22" rx="6" fill="#ffffff" stroke="#e9d5ff" stroke-width="1.2" />
        <text x="423" y="79" font-size="12" fill="#6b21a8" font-weight="700" text-anchor="middle" dominant-baseline="middle">Amplitude (A)</text>

        
        <circle cx="120" cy="52" r="4" fill="#2563eb" />
        <text x="120" y="69" font-size="11.5" fill="#1e2945" font-weight="700" text-anchor="middle">Crest</text>

        <circle cx="360" cy="52" r="4" fill="#2563eb" />
        <text x="360" y="45" font-size="11.5" fill="#1e2945" font-weight="700" text-anchor="middle">Crest</text>

        <circle cx="240" cy="138" r="4" fill="#2563eb" />
        <text x="240" y="156" font-size="11.5" fill="#1e2945" font-weight="700" text-anchor="middle">Trough</text>
      </svg>
    </div>
  </div>

  
  <div class="panel">
    <div class="panel-header">
      <span class="panel-title">Longitudinal Wave</span>
      <span class="legend-tag tag-teal">Wavelength (λ)</span>
    </div>

    <div class="svg-wrap">
      <svg viewBox="0 0 540 150" preserveAspectRatio="xMidYMid meet">
        
        <text x="120" y="18" font-size="12" fill="#1e2945" font-weight="700" text-anchor="middle">Compression</text>
        <text x="240" y="18" font-size="12" fill="#64748b" font-weight="600" text-anchor="middle">Rarefaction</text>
        <text x="360" y="18" font-size="12" fill="#1e2945" font-weight="700" text-anchor="middle">Compression</text>

        
        <rect x="20" y="28" width="480" height="52" rx="6" fill="#f1f5f9" stroke="#e2e8f0" stroke-width="1" />

        
        <g id="particleGroup"></g>

        
        <line x1="120" y1="28" x2="120" y2="100" stroke="#cbd5e1" stroke-width="1.2" stroke-dasharray="3,3" />
        <line x1="360" y1="28" x2="360" y2="100" stroke="#cbd5e1" stroke-width="1.2" stroke-dasharray="3,3" />

        
        <line x1="124" y1="104" x2="356" y2="104" stroke="#0d9488" stroke-width="2" marker-start="url(#arrow-teal-left)" marker-end="url(#arrow-teal-right)" />
        <rect x="180" y="93" width="120" height="22" rx="6" fill="#ffffff" stroke="#99f6e4" stroke-width="1.2" />
        <text x="240" y="109" font-size="12" fill="#0f766e" font-weight="700" text-anchor="middle" dominant-baseline="middle">Wavelength (λ)</text>
      </svg>
    </div>
  </div>

</div>

<script>
  // Draw mathematically exact Sine Wave
  const sinePath = document.getElementById('sinePath');
  let d = '';
  const x0 = 20, x1 = 435;
  const yCenter = 95;
  const amp = 43;
  const wavelength = 240; // Crests at x = 120 and x = 360

  for (let x = x0; x <= x1; x += 2) {
    const y = yCenter - amp * Math.sin((2 * Math.PI * (x - 60)) / wavelength);
    d += (x === x0 ? 'M ' : 'L ') + x.toFixed(1) + ' ' + y.toFixed(1) + ' ';
  }
  sinePath.setAttribute('d', d);

  // Generate Longitudinal Wave Particles
  const particleGroup = document.getElementById('particleGroup');
  const numColumns = 70;
  const rowY = [38, 46, 54, 62, 70];

  for (let i = 0; i < numColumns; i++) {
    const baseNormX = i / (numColumns - 1);
    const baseX = 30 + baseNormX * 460;
    
    // Displacement formula for longitudinal wave:
    // Compressions at x = 120 and x = 360
    const phase = (2 * Math.PI * (baseX - 60)) / wavelength;
    const displacement = -11 * Math.sin(phase);
    const finalX = baseX + displacement;

    rowY.forEach(y => {
      const dot = document.createElementNS('http://www.w3.org/2000/svg', 'circle');
      dot.setAttribute('cx', finalX.toFixed(1));
      dot.setAttribute('cy', y);
      dot.setAttribute('r', '2');
      dot.setAttribute('fill', '#0284c7');
      particleGroup.appendChild(dot);
    });
  }
</script>

</body>
</html>

Wave Properties: Transverse and Longitudinal Waves

<!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>Wave Speed Equation</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }

    body {
      width: 100%;
      min-height: 100%;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 12px;
    }

    .main-wrap {
      width: 100%;
      max-width: 520px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    /* Interactive Top Section */
    .top-panel {
      display: flex;
      flex-direction: row;
      align-items: center;
      justify-content: space-around;
      gap: 12px;
      background: #f8fafc;
      border-radius: 12px;
      padding: 10px 14px;
    }

    /* Formula Triangle */
    .triangle-box {
      position: relative;
      width: 140px;
      height: 120px;
      flex-shrink: 0;
    }

    .triangle-svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }

    .tri-btn {
      cursor: pointer;
      transition: opacity 0.2s, filter 0.2s;
    }

    .tri-btn:hover {
      filter: brightness(0.95);
    }

    .tri-btn text {
      font-weight: 800;
      font-size: 20px;
      text-anchor: middle;
      dominant-baseline: central;
      user-select: none;
      pointer-events: none;
    }

    .op-symbol {
      font-size: 13px;
      font-weight: 700;
      fill: #64748b;
      text-anchor: middle;
      dominant-baseline: central;
      user-select: none;
    }

    /* Equation Display */
    .equation-display {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      flex-grow: 1;
      text-align: center;
      min-height: 80px;
    }

    .eq-target {
      font-size: 12px;
      font-weight: 600;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      color: #64748b;
      margin-bottom: 4px;
    }

    .eq-math {
      font-size: 26px;
      font-weight: 800;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      color: #1e2945;
    }

    .frac {
      display: inline-flex;
      flex-direction: column;
      align-items: center;
      vertical-align: middle;
      font-size: 22px;
      line-height: 1;
      padding: 0 4px;
    }

    .frac-top {
      border-bottom: 2px solid #1e2945;
      padding-bottom: 2px;
      width: 100%;
      text-align: center;
    }

    .frac-bot {
      padding-top: 2px;
      width: 100%;
      text-align: center;
    }

    /* Variable Cards */
    .cards-row {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 8px;
    }

    .var-card {
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 10px;
      padding: 10px 8px;
      text-align: center;
      cursor: pointer;
      transition: border-color 0.2s, box-shadow 0.2s, background-color 0.2s;
      user-select: none;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 4px;
    }

    .var-card.v-active {
      border-color: #2563eb;
      background: #eff6ff;
      box-shadow: 0 0 0 1px #2563eb;
    }

    .var-card.f-active {
      border-color: #16a34a;
      background: #f0fdf4;
      box-shadow: 0 0 0 1px #16a34a;
    }

    .var-card.l-active {
      border-color: #d97706;
      background: #fffbeb;
      box-shadow: 0 0 0 1px #d97706;
    }

    .var-symbol {
      font-size: 20px;
      font-weight: 800;
      line-height: 1;
    }

    .var-name {
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
    }

    .var-unit {
      font-size: 11px;
      font-weight: 600;
      color: #64748b;
    }

    .c-v { color: #2563eb; }
    .c-f { color: #16a34a; }
    .c-l { color: #d97706; }

    /* Unit Proof Badge */
    .unit-proof {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 8px 12px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 13px;
      font-weight: 600;
    }

    .unit-proof-tag {
      background: #e2e8f0;
      color: #334155;
      padding: 2px 6px;
      border-radius: 4px;
      font-size: 11px;
      font-weight: 700;
      letter-spacing: 0.5px;
    }

    .unit-proof-math {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      color: #1e2945;
    }

    .unit-proof-math .frac {
      font-size: 13px;
    }

    .unit-proof-math .frac-top {
      border-bottom-width: 1.5px;
    }

    @media (max-width: 400px) {
      .top-panel {
        flex-direction: column;
        padding: 8px;
      }
      .triangle-box {
        width: 130px;
        height: 110px;
      }
      .cards-row {
        gap: 6px;
      }
      .var-name {
        font-size: 12px;
      }
      .var-unit {
        font-size: 10px;
      }
      .unit-proof {
        font-size: 12px;
        padding: 6px 8px;
      }
    }
  </style>
</head>
<body>

  <div class="main-wrap">
    
    <div class="top-panel">
      
      <div class="triangle-box">
        <svg class="triangle-svg" viewBox="0 0 140 120">
          
          <polygon points="70,6 6,114 134,114" fill="#ffffff" stroke="#cbd5e1" stroke-width="2" stroke-linejoin="round"/>
          
          
          <line x1="38" y1="60" x2="102" y2="60" stroke="#cbd5e1" stroke-width="2" />
          <line x1="70" y1="60" x2="70" y2="114" stroke="#cbd5e1" stroke-width="2" />

          
          <polygon id="btn-v" class="tri-btn" points="70,8 40,59 100,59" fill="#eff6ff" stroke="#2563eb" stroke-width="2" />
          <text x="70" y="40" fill="#2563eb">v</text>

          
          <polygon id="btn-f" class="tri-btn" points="8,112 37,61 69,61 69,112" fill="#f8fafc" stroke="transparent" stroke-width="2" />
          <text x="43" y="88" fill="#16a34a">f</text>

          
          <polygon id="btn-l" class="tri-btn" points="71,61 103,61 132,112 71,112" fill="#f8fafc" stroke="transparent" stroke-width="2" />
          <text x="97" y="88" fill="#d97706">λ</text>

          
          <text x="70" y="88" class="op-symbol">×</text>
        </svg>
      </div>

      
      <div class="equation-display" id="eq-container">
        <span class="eq-target" id="eq-target-label">Speed Formula</span>
        <div class="eq-math" id="eq-math-display">
          <span class="c-v">v</span>
          <span>=</span>
          <span class="c-f">f</span>
          <span>×</span>
          <span class="c-l">λ</span>
        </div>
      </div>
    </div>

    
    <div class="cards-row">
      <div class="var-card v-active" id="card-v">
        <span class="var-symbol c-v">v</span>
        <span class="var-name">Speed</span>
        <span class="var-unit">m/s</span>
      </div>

      <div class="var-card" id="card-f">
        <span class="var-symbol c-f">f</span>
        <span class="var-name">Frequency</span>
        <span class="var-unit">Hz (1/s)</span>
      </div>

      <div class="var-card" id="card-l">
        <span class="var-symbol c-l">λ</span>
        <span class="var-name">Wavelength</span>
        <span class="var-unit">meters (m)</span>
      </div>
    </div>

    
    <div class="unit-proof">
      <span class="unit-proof-tag">UNIT PROOF</span>
      <div class="unit-proof-math">
        <span>1 Hz = <span class="frac"><span class="frac-top">1</span><span class="frac-bot">s</span></span></span>
        <span>→</span>
        <span><span class="frac"><span class="frac-top">1</span><span class="frac-bot">s</span></span> × m = <span class="frac"><span class="frac-top">m</span><span class="frac-bot">s</span></span></span>
      </div>
    </div>
  </div>

  <script>
    const modes = {
      v: {
        label: 'Calculate Speed',
        html: '<span class="c-v">v</span> <span>=</span> <span class="c-f">f</span> <span>×</span> <span class="c-l">λ</span>',
        btnBg: '#eff6ff',
        btnStroke: '#2563eb'
      },
      f: {
        label: 'Calculate Frequency',
        html: '<span class="c-f">f</span> <span>=</span> <span class="frac"><span class="frac-top c-v">v</span><span class="frac-bot c-l">λ</span></span>',
        btnBg: '#f0fdf4',
        btnStroke: '#16a34a'
      },
      l: {
        label: 'Calculate Wavelength',
        html: '<span class="c-l">λ</span> <span>=</span> <span class="frac"><span class="frac-top c-v">v</span><span class="frac-bot c-f">f</span></span>',
        btnBg: '#fffbeb',
        btnStroke: '#d97706'
      }
    };

    const btns = {
      v: document.getElementById('btn-v'),
      f: document.getElementById('btn-f'),
      l: document.getElementById('btn-l')
    };

    const cards = {
      v: document.getElementById('card-v'),
      f: document.getElementById('card-f'),
      l: document.getElementById('card-l')
    };

    const labelEl = document.getElementById('eq-target-label');
    const mathEl = document.getElementById('eq-math-display');

    function selectVariable(key) {
      // Update Triangle Polygons
      Object.keys(btns).forEach(k => {
        if (k === key) {
          btns[k].setAttribute('fill', modes[k].btnBg);
          btns[k].setAttribute('stroke', modes[k].btnStroke);
        } else {
          btns[k].setAttribute('fill', '#f8fafc');
          btns[k].setAttribute('stroke', 'transparent');
        }
      });

      // Update Cards
      cards.v.className = 'var-card' + (key === 'v' ? ' v-active' : '');
      cards.f.className = 'var-card' + (key === 'f' ? ' f-active' : '');
      cards.l.className = 'var-card' + (key === 'l' ? ' l-active' : '');

      // Update Math Display
      labelEl.textContent = modes[key].label;
      mathEl.innerHTML = modes[key].html;
    }

    // Attach click events
    Object.keys(btns).forEach(k => {
      btns[k].addEventListener('click', () => selectVariable(k));
      cards[k].addEventListener('click', () => selectVariable(k));
    });
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
      user-select: none;
    }

    body {
      background: #ffffff;
      color: #1e2945;
      width: 100%;
      max-width: 680px;
      margin: 0 auto;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 10px;
    }

    .wave-card {
      background: #ffffff;
      border: 1px solid #e6e6e6;
      border-radius: 10px;
      padding: 10px 12px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .card-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
      flex-wrap: wrap;
      gap: 6px;
    }

    .pill-group {
      display: flex;
      gap: 6px;
      font-size: 11px;
      font-weight: 600;
    }

    .pill {
      display: inline-flex;
      align-items: center;
      gap: 4px;
      padding: 2px 8px;
      border-radius: 12px;
      line-height: 1.2;
      white-space: nowrap;
    }

    .pill-wave {
      background: #eff6ff;
      color: #2563eb;
      border: 1px solid #bfdbfe;
    }

    .pill-particle {
      background: #fef2f2;
      color: #dc2626;
      border: 1px solid #fecaca;
    }

    .canvas-container {
      position: relative;
      width: 100%;
      height: 132px;
      background: #f8fafc;
      border-radius: 6px;
      overflow: hidden;
      border: 1px solid #f1f5f9;
    }

    canvas {
      display: block;
      width: 100%;
      height: 100%;
    }

    .controls {
      display: flex;
      justify-content: center;
      gap: 12px;
      align-items: center;
      padding-top: 2px;
    }

    .btn {
      background: #ffffff;
      border: 1px solid #d1d5db;
      color: #1e2945;
      padding: 6px 14px;
      border-radius: 6px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      transition: background 0.15s ease, border-color 0.15s ease;
    }

    .btn:hover {
      background: #f8fafc;
      border-color: #94a3b8;
    }

    .btn:active {
      background: #f1f5f9;
    }
  </style>
</head>
<body>

  
  <div class="wave-card">
    <div class="card-header">
      <span>Transverse Wave</span>
      <div class="pill-group">
        <span class="pill pill-particle">Particle ↕</span>
        <span class="pill pill-wave">Wave →</span>
      </div>
    </div>
    <div class="canvas-container">
      <canvas id="transverseCanvas"></canvas>
    </div>
  </div>

  
  <div class="wave-card">
    <div class="card-header">
      <span>Longitudinal Wave</span>
      <div class="pill-group">
        <span class="pill pill-particle">Particle ↔</span>
        <span class="pill pill-wave">Wave →</span>
      </div>
    </div>
    <div class="canvas-container">
      <canvas id="longitudinalCanvas"></canvas>
    </div>
  </div>

  
  <div class="controls">
    <button class="btn" id="playBtn">⏸ Pause</button>
    <button class="btn" id="speedBtn">⚡ Normal Speed</button>
  </div>

  <script>
    const tCanvas = document.getElementById('transverseCanvas');
    const lCanvas = document.getElementById('longitudinalCanvas');
    const tCtx = tCanvas.getContext('2d');
    const lCtx = lCanvas.getContext('2d');
    const playBtn = document.getElementById('playBtn');
    const speedBtn = document.getElementById('speedBtn');

    let isPlaying = true;
    let speed = 1.0;
    let time = 0;
    let lastTimestamp = 0;

    function resizeCanvases() {
      const dpr = window.devicePixelRatio || 1;
      [tCanvas, lCanvas].forEach(canvas => {
        const rect = canvas.getBoundingClientRect();
        canvas.width = rect.width * dpr;
        canvas.height = rect.height * dpr;
      });
    }

    window.addEventListener('resize', resizeCanvases);
    resizeCanvases();

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

    speedBtn.addEventListener('click', () => {
      if (speed === 1.0) {
        speed = 0.35;
        speedBtn.textContent = '🐢 Slow Motion';
      } else {
        speed = 1.0;
        speedBtn.textContent = '⚡ Normal Speed';
      }
    });

    function drawArrow(ctx, fromX, fromY, toX, toY, color) {
      const headlen = 5;
      const angle = Math.atan2(toY - fromY, toX - fromX);
      ctx.strokeStyle = color;
      ctx.fillStyle = color;
      ctx.lineWidth = 1.5;
      ctx.beginPath();
      ctx.moveTo(fromX, fromY);
      ctx.lineTo(toX, toY);
      ctx.stroke();
      ctx.beginPath();
      ctx.moveTo(toX, toY);
      ctx.lineTo(toX - headlen * Math.cos(angle - Math.PI / 6), toY - headlen * Math.sin(angle - Math.PI / 6));
      ctx.lineTo(toX - headlen * Math.cos(angle + Math.PI / 6), toY - headlen * Math.sin(angle + Math.PI / 6));
      ctx.fill();
    }

    function render(timestamp) {
      if (!lastTimestamp) lastTimestamp = timestamp;
      const dt = (timestamp - lastTimestamp) / 1000;
      lastTimestamp = timestamp;

      if (isPlaying) {
        // ~1.5s per cycle base rate
        time += dt * speed * ((Math.PI * 2) / 1.5);
      }

      const dpr = window.devicePixelRatio || 1;
      const w = tCanvas.width / dpr;
      const h = tCanvas.height / dpr;

      // ----------------------------------------------------
      // 1. TRANSVERSE WAVE
      // ----------------------------------------------------
      tCtx.save();
      tCtx.scale(dpr, dpr);
      tCtx.clearRect(0, 0, w, h);

      const tMidY = h * 0.5;
      const tAmp = Math.min(24, h * 0.2);
      const tWavelength = Math.max(180, w * 0.65);
      const k = (Math.PI * 2) / tWavelength;

      // Equilibrium dashed line
      tCtx.strokeStyle = '#e2e8f0';
      tCtx.setLineDash([4, 4]);
      tCtx.lineWidth = 1;
      tCtx.beginPath();
      tCtx.moveTo(0, tMidY);
      tCtx.lineTo(w, tMidY);
      tCtx.stroke();
      tCtx.setLineDash([]);

      // Continuous wave line
      tCtx.strokeStyle = '#93c5fd';
      tCtx.lineWidth = 2.5;
      tCtx.beginPath();
      for (let x = 0; x <= w; x += 2) {
        const y = tMidY - tAmp * Math.sin(k * x - time);
        if (x === 0) tCtx.moveTo(x, y);
        else tCtx.lineTo(x, y);
      }
      tCtx.stroke();

      // Particle beads along the rope
      const beadCount = 38;
      const trackedIndex = Math.floor(beadCount * 0.42);
      let trackedX = 0;
      let trackedY = 0;

      for (let i = 0; i <= beadCount; i++) {
        const bx = (i / beadCount) * w;
        const by = tMidY - tAmp * Math.sin(k * bx - time);

        if (i === trackedIndex) {
          trackedX = bx;
          trackedY = by;
        } else {
          tCtx.fillStyle = '#60a5fa';
          tCtx.beginPath();
          tCtx.arc(bx, by, 3, 0, Math.PI * 2);
          tCtx.fill();
        }
      }

      // Vertical oscillation track for highlighted particle
      tCtx.strokeStyle = '#fca5a5';
      tCtx.setLineDash([3, 3]);
      tCtx.beginPath();
      tCtx.moveTo(trackedX, tMidY - tAmp - 4);
      tCtx.lineTo(trackedX, tMidY + tAmp + 4);
      tCtx.stroke();
      tCtx.setLineDash([]);

      // Highlighted oscillating red particle
      tCtx.fillStyle = '#ef4444';
      tCtx.beginPath();
      tCtx.arc(trackedX, trackedY, 5.5, 0, Math.PI * 2);
      tCtx.fill();
      tCtx.strokeStyle = '#ffffff';
      tCtx.lineWidth = 1.5;
      tCtx.stroke();

      // Find visible Crest and Trough closest to center
      let crestX = ((Math.PI / 2 + time) / k) % tWavelength;
      while (crestX < w * 0.15) crestX += tWavelength;
      while (crestX > w * 0.85) crestX -= tWavelength;
      const crestY = tMidY - tAmp;

      let troughX = ((3 * Math.PI / 2 + time) / k) % tWavelength;
      while (troughX < w * 0.15) troughX += tWavelength;
      while (troughX > w * 0.85) troughX -= tWavelength;
      const troughY = tMidY + tAmp;

      // Crest label (safe vertical clearance from top)
      if (crestX > 25 && crestX < w - 25) {
        tCtx.fillStyle = '#1e2945';
        tCtx.font = '600 11px system-ui, -apple-system, sans-serif';
        tCtx.textAlign = 'center';
        tCtx.fillText('Crest', crestX, 14);
        drawArrow(tCtx, crestX, 18, crestX, crestY - 4, '#2563eb');
      }

      // Trough label (safe vertical clearance from bottom)
      if (troughX > 25 && troughX < w - 25) {
        tCtx.fillStyle = '#1e2945';
        tCtx.font = '600 11px system-ui, -apple-system, sans-serif';
        tCtx.textAlign = 'center';
        tCtx.fillText('Trough', troughX, h - 9);
        drawArrow(tCtx, troughX, h - 22, troughX, troughY + 4, '#2563eb');
      }

      tCtx.restore();

      // ----------------------------------------------------
      // 2. LONGITUDINAL WAVE
      // ----------------------------------------------------
      lCtx.save();
      lCtx.scale(dpr, dpr);
      lCtx.clearRect(0, 0, w, h);

      const lAmp = 13;
      const lWavelength = Math.max(180, w * 0.65);
      const lk = (Math.PI * 2) / lWavelength;
      const cols = 42;
      const rows = 5;

      // Vertical bounds: particles constrained to middle area to prevent text overlap
      const topPad = 32;
      const botPad = 32;
      const gridHeight = h - topPad - botPad;
      const rowSpacing = gridHeight / (rows - 1);

      const trackedCol = Math.floor(cols * 0.42);
      let lTrackedX = 0;
      let lTrackedBaseX = 0;
      let lTrackedY = topPad + Math.floor(rows / 2) * rowSpacing;

      // Draw particles
      for (let c = 0; c < cols; c++) {
        const baseX = (c / (cols - 1)) * (w + 40) - 20;
        const disp = -lAmp * Math.sin(lk * baseX - time);
        const curX = baseX + disp;

        if (c === trackedCol) {
          lTrackedX = curX;
          lTrackedBaseX = baseX;
        }

        for (let r = 0; r < rows; r++) {
          const py = topPad + r * rowSpacing;
          if (c === trackedCol && r === Math.floor(rows / 2)) {
            lTrackedY = py;
            continue;
          }
          lCtx.fillStyle = '#64748b';
          lCtx.beginPath();
          lCtx.arc(curX, py, 2.5, 0, Math.PI * 2);
          lCtx.fill();
        }
      }

      // Horizontal oscillation track for highlighted particle
      lCtx.strokeStyle = '#fca5a5';
      lCtx.setLineDash([3, 3]);
      lCtx.beginPath();
      lCtx.moveTo(lTrackedBaseX - lAmp - 6, lTrackedY);
      lCtx.lineTo(lTrackedBaseX + lAmp + 6, lTrackedY);
      lCtx.stroke();
      lCtx.setLineDash([]);

      // Highlighted red particle
      lCtx.fillStyle = '#ef4444';
      lCtx.beginPath();
      lCtx.arc(lTrackedX, lTrackedY, 5.5, 0, Math.PI * 2);
      lCtx.fill();
      lCtx.strokeStyle = '#ffffff';
      lCtx.lineWidth = 1.5;
      lCtx.stroke();

      // Find visible Compression and Rarefaction positions
      let compX = (time / lk) % lWavelength;
      while (compX < w * 0.2) compX += lWavelength;
      while (compX > w * 0.8) compX -= lWavelength;

      let rarefX = ((time + Math.PI) / lk) % lWavelength;
      while (rarefX < w * 0.2) rarefX += lWavelength;
      while (rarefX > w * 0.8) rarefX -= lWavelength;

      // Labels outside particle field with dark navy text and clear blue arrows
      lCtx.font = '600 11px system-ui, -apple-system, sans-serif';
      lCtx.textAlign = 'center';

      if (compX > 35 && compX < w - 35) {
        lCtx.fillStyle = '#1e2945';
        lCtx.fillText('Compression', compX, 14);
        drawArrow(lCtx, compX, 18, compX, topPad - 4, '#2563eb');
      }

      if (rarefX > 35 && rarefX < w - 35) {
        lCtx.fillStyle = '#1e2945';
        lCtx.fillText('Rarefaction', rarefX, h - 9);
        drawArrow(lCtx, rarefX, h - 22, rarefX, topPad + gridHeight + 4, '#2563eb');
      }

      lCtx.restore();

      requestAnimationFrame(render);
    }

    requestAnimationFrame(render);
  </script>
</body>
</html>

OGS.7.PS.10

Aligned learning resources

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