<!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;
      -webkit-font-smoothing: antialiased;
    }

    body {
      width: 100%;
      background: transparent;
      color: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .panel {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px 14px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .panel-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      flex-wrap: wrap;
      gap: 6px;
    }

    .badge {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      font-size: 13px;
      font-weight: 700;
      padding: 4px 10px;
      border-radius: 20px;
      letter-spacing: 0.2px;
    }

    .badge-success {
      background: #ecfdf5;
      color: #059669;
      border: 1px solid #a7f3d0;
    }

    .badge-error {
      background: #fff1f2;
      color: #e11d48;
      border: 1px solid #fecdd3;
    }

    .tag {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
    }

    .svg-container {
      width: 100%;
      height: auto;
      aspect-ratio: 540 / 110;
    }

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

    .legend-row {
      display: flex;
      justify-content: center;
      align-items: center;
      gap: 16px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      flex-wrap: wrap;
    }

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

    .key-line {
      width: 18px;
      height: 3px;
      border-radius: 2px;
    }

    .key-dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
    }

    .controls {
      display: flex;
      justify-content: center;
      gap: 8px;
    }

    .btn {
      background: #f8fafc;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 6px 14px;
      border-radius: 8px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 6px;
      user-select: none;
    }

    .btn:active {
      background: #e2e8f0;
    }

    .alias-wave {
      transition: opacity 0.3s ease;
    }
  </style>
</head>
<body>

  
  <div class="panel">
    <div class="panel-header">
      <span class="badge badge-success">✓ Sufficient: <i>f</i><sub>s</sub> &gt; 2<i>f</i></span>
      <span class="tag">Exact Reconstruction</span>
    </div>
    <div class="svg-container">
      <svg id="svgSufficient" viewBox="0 0 540 110">
        
        <line x1="15" y1="55" x2="525" y2="55" stroke="#f1f5f9" stroke-width="2" />
        
        <path id="pathSufficient" fill="none" stroke="#2563eb" stroke-width="2.5" />
        
        <g id="dotsSufficient"></g>
      </svg>
    </div>
  </div>

  
  <div class="panel">
    <div class="panel-header">
      <span class="badge badge-error">⚠ Undersampled: <i>f</i><sub>s</sub> &lt; 2<i>f</i></span>
      <span class="tag">False Low Frequency</span>
    </div>
    <div class="svg-container">
      <svg id="svgUndersampled" viewBox="0 0 540 110">
        
        <line x1="15" y1="55" x2="525" y2="55" stroke="#f1f5f9" stroke-width="2" />
        
        <path id="pathOriginal" fill="none" stroke="#93c5fd" stroke-width="1.8" stroke-dasharray="4 3" />
        
        <path id="pathAlias" class="alias-wave" fill="none" stroke="#e11d48" stroke-width="3" stroke-dasharray="6 4" />
        
        <g id="dotsUndersampled"></g>
      </svg>
    </div>
  </div>

  
  <div class="legend-row">
    <div class="legend-item">
      <div class="key-line" style="background: #2563eb;"></div>
      <span>Original Signal (<i>f</i>)</span>
    </div>
    <div class="legend-item">
      <div class="key-dot" style="background: #1e2945; border: 2px solid #ffffff; box-shadow: 0 0 0 1px #1e2945;"></div>
      <span>Sample Points (<i>f</i><sub>s</sub>)</span>
    </div>
    <div class="legend-item">
      <div class="key-line" style="background: #e11d48; border-top: 2px dashed #e11d48; height: 0;"></div>
      <span>Alias Wave (<i>f</i><sub>alias</sub>)</span>
    </div>
  </div>

  <div class="controls">
    <button class="btn" id="toggleBtn" onclick="toggleAlias()">
      <span id="btnIcon">👁</span> <span id="btnText">Hide Alias Wave</span>
    </button>
  </div>

  <script>
    const W = 480;
    const X0 = 30;
    const Y_MID = 55;
    const AMP = 38;
    const CYCLES = 6;
    const PERIOD = W / CYCLES; // 80px per cycle

    // 1. Plot Original Wave Path
    function getSinePath(cycles, amp, offset = 0) {
      let d = "";
      for (let x = 0; x <= W; x += 2) {
        const rad = (2 * Math.PI * (x / (W / cycles))) + offset;
        const y = Y_MID - amp * Math.sin(rad);
        d += (x === 0 ? "M" : "L") + (X0 + x) + "," + y.toFixed(2);
      }
      return d;
    }

    document.getElementById("pathSufficient").setAttribute("d", getSinePath(CYCLES, AMP));
    document.getElementById("pathOriginal").setAttribute("d", getSinePath(CYCLES, AMP));

    // 2. Generate Sufficient Samples (fs = 4 * f -> 4 points per cycle = 20px step)
    const dotsSuffGroup = document.getElementById("dotsSufficient");
    const stepSuff = PERIOD / 4; // 20px
    for (let x = 0; x <= W; x += stepSuff) {
      const rad = 2 * Math.PI * (x / PERIOD);
      const y = Y_MID - AMP * Math.sin(rad);
      
      const dot = document.createElementNS("http://www.w3.org/2000/svg", "circle");
      dot.setAttribute("cx", X0 + x);
      dot.setAttribute("cy", y);
      dot.setAttribute("r", "4");
      dot.setAttribute("fill", "#1e2945");
      dot.setAttribute("stroke", "#ffffff");
      dot.setAttribute("stroke-width", "1.5");
      dotsSuffGroup.appendChild(dot);
    }

    // 3. Undersampling (fs = 1.2 * f -> step = 96px).
    // Aliasing produces apparent frequency f_alias = |fs - f| = |1.2 - 1|f = 0.2f = 1 cycle across 480px!
    const stepUnder = PERIOD * 1.2; // 96px
    const dotsUnderGroup = document.getElementById("dotsUndersampled");

    for (let x = 0; x <= W; x += stepUnder) {
      const rad = 2 * Math.PI * (x / PERIOD);
      const y = Y_MID - AMP * Math.sin(rad);

      // Dot
      const dot = document.createElementNS("http://www.w3.org/2000/svg", "circle");
      dot.setAttribute("cx", X0 + x);
      dot.setAttribute("cy", y);
      dot.setAttribute("r", "4.5");
      dot.setAttribute("fill", "#e11d48");
      dot.setAttribute("stroke", "#ffffff");
      dot.setAttribute("stroke-width", "1.5");
      dotsUnderGroup.appendChild(dot);
    }

    // 4. Aliased Sine Wave (1 full cycle over W = 480px)
    document.getElementById("pathAlias").setAttribute("d", getSinePath(1, AMP));

    // Interactive Toggle
    let aliasVisible = true;
    function toggleAlias() {
      aliasVisible = !aliasVisible;
      const aliasPath = document.getElementById("pathAlias");
      const btnText = document.getElementById("btnText");
      const btnIcon = document.getElementById("btnIcon");

      if (aliasVisible) {
        aliasPath.style.opacity = "1";
        btnText.textContent = "Hide Alias Wave";
        btnIcon.textContent = "👁";
      } else {
        aliasPath.style.opacity = "0";
        btnText.textContent = "Show Alias Wave";
        btnIcon.textContent = "✨";
      }
    }
  </script>
</body>
</html>

Sampling Rate, Nyquist Theorem, and Aliasing

<!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: #f8fafc;
      color: #1e293b;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }
    .wrapper {
      width: 100%;
      max-width: 480px;
      display: flex;
      flex-direction: column;
      gap: 10px;
    }
    .svg-container {
      width: 100%;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      overflow: hidden;
    }
    svg {
      display: block;
      width: 100%;
      height: auto;
    }
    .controls {
      display: flex;
      flex-direction: column;
      gap: 8px;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 10px 12px;
    }
    .slider-row {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 10px;
      font-size: 13px;
      font-weight: 600;
    }
    input[type="range"] {
      flex: 1;
      accent-color: #2563eb;
      cursor: pointer;
    }
    .presets {
      display: flex;
      gap: 6px;
      justify-content: center;
    }
    .preset-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 4px;
      padding: 4px 10px;
      font-size: 12px;
      font-weight: 600;
      color: #334155;
      cursor: pointer;
      transition: background 0.2s, border-color 0.2s;
    }
    .preset-btn.active {
      background: #2563eb;
      border-color: #1d4ed8;
      color: #ffffff;
    }
    .math-callout {
      text-align: center;
      font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
      font-size: 13px;
      font-weight: 700;
      color: #0f172a;
      background: #f1f5f9;
      padding: 6px 10px;
      border-radius: 6px;
      border: 1px solid #e2e8f0;
    }
    .math-callout span.alias { color: #dc2626; }
    .math-callout span.nyq { color: #2563eb; }
  </style>
</head>
<body>

<div class="wrapper">
  <div class="svg-container">
    <svg viewBox="0 0 460 250">
      <defs>
        
        <marker id="arrow-blue" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1 L 10 5 L 0 9 z" fill="#2563eb"/>
        </marker>
        <marker id="arrow-red" viewBox="0 0 10 10" refX="6" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
          <path d="M 0 1 L 10 5 L 0 9 z" fill="#dc2626"/>
        </marker>
      </defs>

      
      <rect x="35" y="30" width="280.6" height="155" fill="#f0fdf4" opacity="0.8" />
      <text x="40" y="45" font-size="11" font-weight="600" fill="#16a34a">Audible Band (0 – f_N)</text>

      
      <line x1="35" y1="185" x2="435" y2="185" stroke="#94a3b8" stroke-width="1.5" />
      
      
      
      <line x1="35" y1="185" x2="35" y2="191" stroke="#64748b" stroke-width="1.5" />
      <text x="35" y="204" font-size="11" text-anchor="middle" fill="#64748b">0</text>

      
      <line x1="168.3" y1="185" x2="168.3" y2="191" stroke="#64748b" stroke-width="1.5" />
      <text x="168.3" y="204" font-size="11" text-anchor="middle" fill="#64748b">10k</text>

      
      <line x1="301.7" y1="185" x2="301.7" y2="191" stroke="#64748b" stroke-width="1.5" />
      <text x="301.7" y="204" font-size="11" text-anchor="middle" fill="#64748b">20k</text>

      
      <line x1="435" y1="185" x2="435" y2="191" stroke="#64748b" stroke-width="1.5" />
      <text x="435" y="204" font-size="11" text-anchor="middle" fill="#64748b">30k</text>

      <text x="235" y="222" font-size="11" text-anchor="middle" font-weight="600" fill="#64748b">Frequency (Hz)</text>

      
      <line x1="329" y1="20" x2="329" y2="185" stroke="#ef4444" stroke-width="2" stroke-dasharray="4,4" />
      <text x="329" y="16" font-size="11" font-weight="700" text-anchor="middle" fill="#dc2626">f_N = 22.05k</text>
      <text x="329" y="204" font-size="10" font-weight="700" text-anchor="middle" fill="#dc2626">22.05k</text>

      
      <line id="inputSpike" x1="381.7" y1="185" x2="381.7" y2="110" stroke="#2563eb" stroke-width="2.5" stroke-dasharray="3,3" />
      <circle id="inputDot" cx="381.7" cy="110" r="4" fill="#2563eb" />
      <text id="inputLabel" x="381.7" y="100" font-size="11" font-weight="700" text-anchor="middle" fill="#2563eb">26k (Input)</text>

      
      <path id="foldPath" d="M 381.7 110 Q 329 50 276.3 110" fill="none" stroke="#dc2626" stroke-width="1.8" stroke-dasharray="4,3" />

      
      <line id="aliasSpike" x1="276.3" y1="185" x2="276.3" y2="110" stroke="#dc2626" stroke-width="3" />
      <circle id="aliasDot" cx="276.3" cy="110" r="4" fill="#dc2626" />
      <text id="aliasLabel" x="276.3" y="100" font-size="11" font-weight="700" text-anchor="middle" fill="#dc2626">18.1k (Alias)</text>

      
      <path id="foldArrow" d="M 345 68 Q 329 60 310 70" fill="none" stroke="#dc2626" stroke-width="2" marker-end="url(#arrow-red)" />
      <text x="329" y="88" font-size="10" font-weight="600" text-anchor="middle" fill="#dc2626">folds back</text>
    </svg>
  </div>

  <div class="math-callout" id="mathText">
    <span class="nyq">26.0 kHz</span> folds to 44.1 − 26.0 = <span class="alias">18.1 kHz</span>
  </div>

  <div class="controls">
    <div class="slider-row">
      <span>Input Frequency:</span>
      <input type="range" id="freqSlider" min="22.1" max="30.0" step="0.1" value="26.0">
      <span id="sliderVal" style="min-width: 48px; text-align: right;">26.0 kHz</span>
    </div>
    <div class="presets">
      <button class="preset-btn" data-freq="24.0">24.0 kHz</button>
      <button class="preset-btn active" data-freq="26.0">26.0 kHz (Default)</button>
      <button class="preset-btn" data-freq="28.1">28.1 kHz</button>
    </div>
  </div>
</div>

<script>
  const fs = 44.1;
  const fN = 22.05;

  const slider = document.getElementById('freqSlider');
  const sliderVal = document.getElementById('sliderVal');
  const mathText = document.getElementById('mathText');
  const presetBtns = document.querySelectorAll('.preset-btn');

  const inputSpike = document.getElementById('inputSpike');
  const inputDot = document.getElementById('inputDot');
  const inputLabel = document.getElementById('inputLabel');

  const aliasSpike = document.getElementById('aliasSpike');
  const aliasDot = document.getElementById('aliasDot');
  const aliasLabel = document.getElementById('aliasLabel');

  const foldPath = document.getElementById('foldPath');

  function freqToX(f) {
    // 0 kHz -> 35, 30 kHz -> 435
    return 35 + (f / 30) * 400;
  }

  function updateDiagram(fIn) {
    const fAlias = Math.max(0, fs - fIn);
    const xIn = freqToX(fIn);
    const xAlias = freqToX(fAlias);
    const xNyq = freqToX(fN);

    // Update Input
    inputSpike.setAttribute('x1', xIn);
    inputSpike.setAttribute('x2', xIn);
    inputDot.setAttribute('cx', xIn);
    inputLabel.setAttribute('x', xIn);
    inputLabel.textContent = `${fIn.toFixed(1)}k (Input)`;

    // Update Alias
    aliasSpike.setAttribute('x1', xAlias);
    aliasSpike.setAttribute('x2', xAlias);
    aliasDot.setAttribute('cx', xAlias);
    aliasLabel.setAttribute('x', xAlias);
    aliasLabel.textContent = `${fAlias.toFixed(1)}k (Alias)`;

    // Update Fold Arc
    const peakY = Math.max(45, 110 - (fIn - fN) * 12);
    foldPath.setAttribute('d', `M ${xIn} 110 Q ${xNyq} ${peakY} ${xAlias} 110`);

    // Update Text
    sliderVal.textContent = `${fIn.toFixed(1)} kHz`;
    mathText.innerHTML = `<span class="nyq">${fIn.toFixed(1)} kHz</span> folds to 44.1 − ${fIn.toFixed(1)} = <span class="alias">${fAlias.toFixed(1)} kHz</span>`;
  }

  slider.addEventListener('input', (e) => {
    const val = parseFloat(e.target.value);
    presetBtns.forEach(btn => {
      btn.classList.toggle('active', parseFloat(btn.dataset.freq) === val);
    });
    updateDiagram(val);
  });

  presetBtns.forEach(btn => {
    btn.addEventListener('click', () => {
      presetBtns.forEach(b => b.classList.remove('active'));
      btn.classList.add('active');
      const val = parseFloat(btn.dataset.freq);
      slider.value = val;
      updateDiagram(val);
    });
  });

  // Initial draw
  updateDiagram(26.0);
</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;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }
    body {
      width: 100%;
      height: 100%;
      background: #f8fafc;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      padding: 12px;
      overflow: hidden;
    }
    .header-bar {
      width: 100%;
      display: flex;
      justify-content: space-between;
      align-items: center;
      flex-wrap: wrap;
      gap: 8px;
    }
    .badge {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 12px;
      font-size: 13px;
      font-weight: 600;
      color: #1e2945;
      box-shadow: 0 1px 3px rgba(0,0,0,0.05);
    }
    .badge span {
      color: #0284c7;
    }
    .btn-group {
      display: flex;
      gap: 6px;
    }
    button {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 6px 12px;
      font-size: 12px;
      font-weight: 600;
      color: #1e2945;
      cursor: pointer;
      transition: all 0.2s ease;
    }
    button.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
    }
    .canvas-container {
      position: relative;
      width: 100%;
      flex: 1;
      min-height: 220px;
      margin: 8px 0;
    }
    canvas {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
    }
    .footer-bar {
      width: 100%;
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 12px;
      color: #64748b;
      font-weight: 500;
      padding: 0 4px;
    }
    .legend {
      display: flex;
      align-items: center;
      gap: 16px;
    }
    .legend-item {
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .indicator-wave {
      width: 16px;
      height: 3px;
      background: #2563eb;
      border-radius: 2px;
    }
    .indicator-dot {
      width: 8px;
      height: 8px;
      background: #00e5ff;
      border-radius: 50%;
      box-shadow: 0 0 6px #00e5ff;
    }
  </style>
</head>
<body>

  <div class="header-bar">
    <div class="badge" id="rateBadge">
      Sampling Rate: <span id="rateText">44,100 samples/sec (44.1 kHz)</span>
    </div>
    <div class="btn-group">
      <button id="btnLow" onclick="setMode('low')">11.0 kHz</button>
      <button id="btnStandard" class="active" onclick="setMode('standard')">44.1 kHz</button>
      <button id="btnHigh" onclick="setMode('high')">96.0 kHz</button>
    </div>
  </div>

  <div class="canvas-container" id="container">
    <canvas id="pcmCanvas"></canvas>
  </div>

  <div class="footer-bar">
    <div class="legend">
      <div class="legend-item">
        <div class="indicator-wave"></div>
        <span>Continuous Signal</span>
      </div>
      <div class="legend-item">
        <div class="indicator-dot"></div>
        <span>Sample Point (PCM)</span>
      </div>
    </div>
    <div>Interval: <strong style="color:#0284c7">T = 1 / f<sub>s</sub></strong></div>
  </div>

  <script>
    const canvas = document.getElementById('pcmCanvas');
    const ctx = canvas.getContext('2d');
    const container = document.getElementById('container');
    const rateText = document.getElementById('rateText');

    let currentInterval = 32; // pixel interval between samples
    let wavePhase = 0;
    let animId;

    const modes = {
      low: { interval: 64, text: "11,025 samples/sec (11.0 kHz)" },
      standard: { interval: 32, text: "44,100 samples/sec (44.1 kHz)" },
      high: { interval: 16, text: "96,000 samples/sec (96.0 kHz)" }
    };

    function setMode(modeKey) {
      document.getElementById('btnLow').className = modeKey === 'low' ? 'active' : '';
      document.getElementById('btnStandard').className = modeKey === 'standard' ? 'active' : '';
      document.getElementById('btnHigh').className = modeKey === 'high' ? 'active' : '';
      
      currentInterval = modes[modeKey].interval;
      rateText.textContent = modes[modeKey].text;
    }

    function resize() {
      const rect = container.getBoundingClientRect();
      const dpr = window.devicePixelRatio || 1;
      canvas.width = rect.width * dpr;
      canvas.height = rect.height * dpr;
      ctx.resetTransform();
      ctx.scale(dpr, dpr);
    }

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

    function render() {
      const w = container.clientWidth;
      const h = container.clientHeight;
      const midY = h * 0.5;
      const amplitude = h * 0.34;
      const wavelength = w * 0.65;

      ctx.clearRect(0, 0, w, h);

      // Grid Lines
      ctx.strokeStyle = '#e2e8f0';
      ctx.lineWidth = 1;
      ctx.beginPath();
      ctx.moveTo(0, midY);
      ctx.lineTo(w, midY);
      ctx.stroke();

      // Continuous Analog Wave
      ctx.beginPath();
      ctx.strokeStyle = '#2563eb';
      ctx.lineWidth = 3;
      for (let x = 0; x <= w; x++) {
        const angle = ((x - wavePhase) / wavelength) * Math.PI * 2;
        const y = midY - Math.sin(angle) * amplitude;
        if (x === 0) ctx.moveTo(x, y);
        else ctx.lineTo(x, y);
      }
      ctx.stroke();

      // Sample Points & Vertical Stems
      const firstSampleX = 24;
      let intervalDrawn = false;
      let prevX = null;

      for (let x = firstSampleX; x < w - 16; x += currentInterval) {
        const angle = ((x - wavePhase) / wavelength) * Math.PI * 2;
        const y = midY - Math.sin(angle) * amplitude;

        // Vertical Dotted Line
        ctx.beginPath();
        ctx.strokeStyle = 'rgba(2, 132, 199, 0.4)';
        ctx.lineWidth = 1.5;
        ctx.setLineDash([3, 3]);
        ctx.moveTo(x, midY);
        ctx.lineTo(x, y);
        ctx.stroke();
        ctx.setLineDash([]);

        // Glowing Cyan Sample Point
        ctx.beginPath();
        ctx.fillStyle = '#00e5ff';
        ctx.shadowColor = '#00bcd4';
        ctx.shadowBlur = 8;
        ctx.arc(x, y, 4.5, 0, Math.PI * 2);
        ctx.fill();
        ctx.shadowBlur = 0;

        // Base Axis Ticks
        ctx.beginPath();
        ctx.fillStyle = '#64748b';
        ctx.arc(x, midY, 2, 0, Math.PI * 2);
        ctx.fill();

        // T Interval Bracket (Between 2nd and 3rd sample)
        if (prevX !== null && !intervalDrawn && x > 60) {
          const bracketY = midY + amplitude + 16;
          if (bracketY < h - 8) {
            ctx.beginPath();
            ctx.strokeStyle = '#0284c7';
            ctx.lineWidth = 1.5;
            ctx.moveTo(prevX, bracketY - 4);
            ctx.lineTo(prevX, bracketY);
            ctx.lineTo(x, bracketY);
            ctx.lineTo(x, bracketY - 4);
            ctx.stroke();

            ctx.fillStyle = '#0284c7';
            ctx.font = '11px sans-serif';
            ctx.textAlign = 'center';
            ctx.fillText('T', (prevX + x) / 2, bracketY + 12);
            intervalDrawn = true;
          }
        }
        prevX = x;
      }

      wavePhase = (wavePhase + 0.8) % wavelength;
      animId = requestAnimationFrame(render);
    }

    render();
  </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 {
      width: 100%;
      min-height: 100%;
      background: #ffffff;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 16px 12px;
      user-select: none;
    }

    .diagram-grid {
      width: 100%;
      max-width: 620px;
      display: flex;
      flex-direction: column;
      gap: 16px;
      align-items: center;
    }

    /* Bytes Timeline Row */
    .bytes-row {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 10px;
      width: 100%;
    }

    .byte-card {
      background: #f8fafc;
      border: 2px solid #e2e8f0;
      border-radius: 10px;
      padding: 12px 8px;
      text-align: center;
      cursor: pointer;
      transition: all 0.3s ease;
      position: relative;
    }

    .byte-card.active {
      border-color: #3b82f6;
      background: #eff6ff;
      box-shadow: 0 4px 12px rgba(59, 130, 246, 0.15);
    }

    .byte-tag {
      display: inline-block;
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.5px;
      padding: 2px 6px;
      border-radius: 4px;
      margin-bottom: 6px;
      background: #e2e8f0;
      color: #475569;
    }

    .byte-card.active .byte-tag {
      background: #3b82f6;
      color: #ffffff;
    }

    .byte-bin {
      font-family: "SFMono-Regular", Consolas, Menlo, monospace;
      font-size: 14px;
      font-weight: 700;
      color: #0f172a;
      letter-spacing: 1px;
      margin-bottom: 4px;
    }

    .byte-meaning {
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      line-height: 1.3;
    }

    .byte-card.active .byte-meaning {
      color: #1e40af;
    }

    /* Output / Trigger Stage */
    .flow-connector {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-size: 18px;
      color: #94a3b8;
    }

    .flow-connector.active {
      color: #3b82f6;
    }

    .output-card {
      width: 100%;
      background: #f8fafc;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 14px 16px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
      transition: all 0.3s ease;
    }

    .output-card.active {
      border-color: #3b82f6;
      background: #f0fdf4;
    }

    /* Mini Piano Visual */
    .piano-wrap {
      display: flex;
      position: relative;
      background: #0f172a;
      padding: 2px;
      border-radius: 6px;
      box-shadow: inset 0 1px 2px rgba(0,0,0,0.2);
    }

    .key-w {
      width: 22px;
      height: 48px;
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 0 0 3px 3px;
      transition: background 0.2s ease;
    }

    .key-w.highlight {
      background: #3b82f6;
    }

    .key-b {
      width: 14px;
      height: 30px;
      background: #1e293b;
      position: absolute;
      z-index: 2;
      border-radius: 0 0 2px 2px;
    }
    .key-b.b1 { left: 16px; }
    .key-b.b2 { left: 38px; }

    .result-info {
      flex: 1;
      text-align: left;
    }

    .result-title {
      font-size: 14px;
      font-weight: 700;
      color: #0f172a;
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .result-desc {
      font-size: 12px;
      color: #64748b;
      margin-top: 2px;
    }

    .action-btn {
      background: #3b82f6;
      color: #ffffff;
      border: none;
      border-radius: 8px;
      padding: 8px 14px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 6px;
      outline: none;
      transition: opacity 0.2s ease;
    }

    .action-btn:active {
      opacity: 0.85;
    }

    /* Navigation Controls */
    .controls-row {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 12px;
      width: 100%;
    }

    .ctrl-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 6px 12px;
      border-radius: 6px;
      font-size: 12px;
      font-weight: 600;
      cursor: pointer;
      transition: background 0.2s ease;
    }

    .ctrl-btn:hover {
      background: #e2e8f0;
    }

    .dots-row {
      display: flex;
      gap: 6px;
    }

    .step-dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: #cbd5e1;
      cursor: pointer;
      transition: background 0.3s ease;
    }

    .step-dot.active {
      background: #3b82f6;
      transform: scale(1.2);
    }
  </style>
</head>
<body>

  <div class="diagram-grid">
    
    <div class="bytes-row">
      <div class="byte-card active" id="byte1" onclick="selectStep(0)">
        <div class="byte-tag">Byte 1 · Status</div>
        <div class="byte-bin">1001 0000</div>
        <div class="byte-meaning">Note-On<br>Channel 1</div>
      </div>

      <div class="byte-card" id="byte2" onclick="selectStep(1)">
        <div class="byte-tag">Byte 2 · Data 1</div>
        <div class="byte-bin">0011 1100</div>
        <div class="byte-meaning">Note 60<br>(Middle C)</div>
      </div>

      <div class="byte-card" id="byte3" onclick="selectStep(2)">
        <div class="byte-tag">Byte 3 · Data 2</div>
        <div class="byte-bin">0110 0100</div>
        <div class="byte-meaning">Velocity 100<br>(mf)</div>
      </div>
    </div>

    <div class="flow-connector" id="flowArrow">↓</div>

    
    <div class="output-card" id="outputCard">
      <div class="piano-wrap">
        <div class="key-w highlight" id="keyC"></div>
        <div class="key-b b1"></div>
        <div class="key-w"></div>
        <div class="key-b b2"></div>
        <div class="key-w"></div>
      </div>
      <div class="result-info">
        <div class="result-title" id="statusHeader">Status: Note-On</div>
        <div class="result-desc" id="statusDesc">MIDI Message Stream Triggered</div>
      </div>
      <button class="action-btn" onclick="triggerNoteSound()">
        <span>🔊</span> Play
      </button>
    </div>

    
    <div class="controls-row">
      <button class="ctrl-btn" onclick="prevStep()">◀ Prev</button>
      <div class="dots-row">
        <div class="step-dot active" onclick="selectStep(0)"></div>
        <div class="step-dot" onclick="selectStep(1)"></div>
        <div class="step-dot" onclick="selectStep(2)"></div>
      </div>
      <button class="ctrl-btn" onclick="nextStep()">Next ▶</button>
    </div>
  </div>

  <script>
    let currentStep = 0;
    const stepData = [
      { title: "Status: Note-On (Ch 1)", desc: "Commands synth to play pitch on Channel 1" },
      { title: "Pitch: Middle C (C4 / 60)", desc: "Designates 261.63 Hz target note frequency" },
      { title: "Velocity: 100 (mf)", desc: "Sets dynamic loudness & key strike intensity" }
    ];

    function updateUI() {
      const cards = [document.getElementById('byte1'), document.getElementById('byte2'), document.getElementById('byte3')];
      const dots = document.querySelectorAll('.step-dot');
      const header = document.getElementById('statusHeader');
      const desc = document.getElementById('statusDesc');

      cards.forEach((card, idx) => {
        card.classList.toggle('active', idx === currentStep);
      });
      dots.forEach((dot, idx) => {
        dot.classList.toggle('active', idx === currentStep);
      });

      header.textContent = stepData[currentStep].title;
      desc.textContent = stepData[currentStep].desc;
    }

    function selectStep(idx) {
      currentStep = idx;
      updateUI();
    }

    function nextStep() {
      currentStep = (currentStep + 1) % 3;
      updateUI();
    }

    function prevStep() {
      currentStep = (currentStep - 1 + 3) % 3;
      updateUI();
    }

    function triggerNoteSound() {
      try {
        const AudioCtx = window.AudioContext || window.webkitAudioContext;
        const ctx = new AudioCtx();
        const osc = ctx.createOscillator();
        const gain = ctx.createGain();
        
        osc.type = 'triangle';
        osc.frequency.setValueAtTime(261.63, ctx.currentTime); // C4 / Middle C
        
        // Velocity 100 / 127 ≈ 0.78 scale
        gain.gain.setValueAtTime(0.35, ctx.currentTime);
        gain.gain.exponentialRampToValueAtTime(0.0001, ctx.currentTime + 0.6);
        
        osc.connect(gain);
        gain.connect(ctx.destination);
        
        osc.start();
        osc.stop(ctx.currentTime + 0.6);

        // Visual flash
        const key = document.getElementById('keyC');
        key.style.background = '#22c55e';
        setTimeout(() => {
          key.style.background = '#3b82f6';
        }, 300);
      } catch (e) {}
    }
  </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: #f8fafc;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e293b;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
    }

    /* Raw Hex Stream */
    .stream {
      display: flex;
      gap: 8px;
      align-items: center;
      margin-bottom: 8px;
    }
    .hex-pill {
      font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
      font-weight: 700;
      font-size: 15px;
      padding: 6px 14px;
      border-radius: 8px;
      background: #ffffff;
      border: 2px solid #e2e8f0;
      color: #64748b;
      transition: all 0.3s ease;
      cursor: pointer;
    }
    .hex-pill.active {
      border-color: #0284c7;
      color: #0284c7;
      background: #f0f9ff;
      box-shadow: 0 0 0 2px rgba(2, 132, 199, 0.2);
    }

    /* Cards Stage */
    .stage {
      position: relative;
      width: 100%;
      max-width: 480px;
      height: 240px;
      perspective: 1000px;
    }
    .step-card {
      position: absolute;
      inset: 0;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 14px;
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      opacity: 0;
      transform: translateY(8px);
      pointer-events: none;
      transition: opacity 0.3s ease, transform 0.3s ease;
      box-shadow: 0 2px 8px rgba(0,0,0,0.04);
    }
    .step-card.active {
      opacity: 1;
      transform: translateY(0);
      pointer-events: auto;
    }

    .card-head {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-weight: 700;
      font-size: 13px;
      color: #64748b;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }
    .badge {
      font-size: 12px;
      padding: 2px 8px;
      border-radius: 6px;
      font-weight: 700;
    }
    .badge-blue { background: #e0f2fe; color: #0369a1; }
    .badge-teal { background: #ccfbf1; color: #0f766e; }
    .badge-amber { background: #fef3c7; color: #b45309; }
    .badge-emerald { background: #dcfce7; color: #15803d; }

    /* Binary & Breakdown Layout */
    .breakdown {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 10px;
      margin: 8px 0;
    }
    .box {
      background: #f8fafc;
      border: 1px solid #f1f5f9;
      border-radius: 8px;
      padding: 10px;
      text-align: center;
    }
    .binary {
      font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
      font-weight: 700;
      font-size: 16px;
      letter-spacing: 1px;
      margin-bottom: 4px;
    }
    .val-blue { color: #0284c7; }
    .val-purple { color: #7c3aed; }
    .val-teal { color: #0d9488; }
    .val-amber { color: #d97706; }

    .tag {
      font-size: 12px;
      font-weight: 600;
      color: #475569;
    }
    .subtag {
      font-size: 11px;
      color: #94a3b8;
      margin-top: 2px;
    }

    /* Result Banner */
    .result-box {
      background: #f0fdf4;
      border: 1.5px solid #86efac;
      border-radius: 8px;
      padding: 10px 14px;
      text-align: center;
    }
    .result-title {
      font-size: 12px;
      font-weight: 700;
      color: #15803d;
      text-transform: uppercase;
      margin-bottom: 2px;
    }
    .result-main {
      font-size: 15px;
      font-weight: 800;
      color: #166534;
    }

    /* Stepper Controls */
    .controls {
      display: flex;
      align-items: center;
      gap: 6px;
      margin-top: 8px;
    }
    .ctrl-btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 6px 12px;
      font-size: 13px;
      font-weight: 600;
      color: #334155;
      cursor: pointer;
    }
    .ctrl-btn:hover { background: #f1f5f9; }
    .dots {
      display: flex;
      gap: 6px;
      padding: 0 8px;
    }
    .dot {
      width: 9px;
      height: 9px;
      border-radius: 50%;
      background: #cbd5e1;
      cursor: pointer;
      transition: background 0.2s;
    }
    .dot.active {
      background: #0284c7;
    }
  </style>
</head>
<body>

  
  <div class="stream">
    <div class="hex-pill active" onclick="goToStep(0)">BA</div>
    <div class="hex-pill" onclick="goToStep(1)">07</div>
    <div class="hex-pill" onclick="goToStep(2)">7F</div>
  </div>

  
  <div class="stage">
    
    <div class="step-card active" id="card-0">
      <div class="card-head">
        <span>Step 1 · Status Byte</span>
        <span class="badge badge-blue">0xBA</span>
      </div>
      <div class="breakdown">
        <div class="box">
          <div class="binary val-blue">1011</div>
          <div class="tag">Control Change</div>
          <div class="subtag">Command Type</div>
        </div>
        <div class="box">
          <div class="binary val-purple">1010</div>
          <div class="tag">Channel 11</div>
          <div class="subtag">Binary 10 (+1)</div>
        </div>
      </div>
      <div class="subtag" style="text-align: center;">MSB = 1 (Status Flag)</div>
    </div>

    
    <div class="step-card" id="card-1">
      <div class="card-head">
        <span>Step 2 · Data 1</span>
        <span class="badge badge-teal">0x07</span>
      </div>
      <div class="breakdown">
        <div class="box" style="grid-column: span 2;">
          <div class="binary val-teal">0000 0111</div>
          <div class="tag">CC 7: Channel Volume</div>
          <div class="subtag">Standard MIDI Controller</div>
        </div>
      </div>
      <div class="subtag" style="text-align: center;">MSB = 0 (Data Flag)</div>
    </div>

    
    <div class="step-card" id="card-2">
      <div class="card-head">
        <span>Step 3 · Data 2</span>
        <span class="badge badge-amber">0x7F</span>
      </div>
      <div class="breakdown">
        <div class="box" style="grid-column: span 2;">
          <div class="binary val-amber">0111 1111</div>
          <div class="tag">Value: 127</div>
          <div class="subtag">7-bit Max (100%)</div>
        </div>
      </div>
      <div class="subtag" style="text-align: center;">Range: 0 - 127</div>
    </div>

    
    <div class="step-card" id="card-3">
      <div class="card-head">
        <span>Decoded Message</span>
        <span class="badge badge-emerald">Complete</span>
      </div>
      <div class="result-box">
        <div class="result-title">Action Executed</div>
        <div class="result-main">Set Ch 11 Volume to 100%</div>
      </div>
      <div class="subtag" style="text-align: center; font-family: ui-monospace, monospace;">
        [CC#7 · Ch 11 · Val 127]
      </div>
    </div>
  </div>

  
  <div class="controls">
    <button class="ctrl-btn" onclick="prevStep()">←</button>
    <div class="dots">
      <div class="dot active" onclick="goToStep(0)"></div>
      <div class="dot" onclick="goToStep(1)"></div>
      <div class="dot" onclick="goToStep(2)"></div>
      <div class="dot" onclick="goToStep(3)"></div>
    </div>
    <button class="ctrl-btn" id="playBtn" onclick="togglePlay()">⏸</button>
    <button class="ctrl-btn" onclick="nextStep()">→</button>
  </div>

  <script>
    let currentStep = 0;
    const totalSteps = 4;
    let timer = null;
    let isPlaying = true;

    const pills = document.querySelectorAll('.hex-pill');
    const cards = document.querySelectorAll('.step-card');
    const dots = document.querySelectorAll('.dot');
    const playBtn = document.getElementById('playBtn');

    function showStep(index) {
      currentStep = index;
      cards.forEach((card, i) => card.classList.toggle('active', i === index));
      dots.forEach((dot, i) => dot.classList.toggle('active', i === index));
      
      pills.forEach((pill, i) => {
        if (index < 3) {
          pill.classList.toggle('active', i === index);
        } else {
          pill.classList.add('active');
        }
      });
    }

    function nextStep() {
      showStep((currentStep + 1) % totalSteps);
    }

    function prevStep() {
      showStep((currentStep - 1 + totalSteps) % totalSteps);
    }

    function goToStep(index) {
      showStep(index);
    }

    function startAuto() {
      if (timer) clearInterval(timer);
      timer = setInterval(nextStep, 3500);
      isPlaying = true;
      playBtn.textContent = '⏸';
    }

    function stopAuto() {
      if (timer) clearInterval(timer);
      isPlaying = false;
      playBtn.textContent = '▶';
    }

    function togglePlay() {
      if (isPlaying) stopAuto();
      else {
        nextStep();
        startAuto();
      }
    }

    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">
  <title>Audio Signal vs. MIDI Data</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: #1e2945;
      padding: 12px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      user-select: none;
    }
    .header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      max-width: 620px;
      margin-bottom: 8px;
    }
    .trigger-btn {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      background: #2563eb;
      color: #ffffff;
      border: none;
      border-radius: 8px;
      padding: 8px 16px;
      font-size: 14px;
      font-weight: 600;
      cursor: pointer;
      box-shadow: 0 2px 4px rgba(37, 99, 235, 0.25);
      transition: opacity 0.2s, transform 0.1s;
    }
    .trigger-btn:active {
      transform: translateY(1px);
    }
    .grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      width: 100%;
      max-width: 620px;
      flex: 1;
    }
    @media (max-width: 480px) {
      .grid {
        grid-template-columns: 1fr;
        gap: 10px;
      }
    }
    .panel {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px;
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      position: relative;
    }
    .panel-title {
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
      padding-bottom: 6px;
      border-bottom: 1px solid #f1f5f9;
    }
    .tag {
      font-size: 11px;
      font-weight: 700;
      padding: 2px 6px;
      border-radius: 4px;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }
    .tag-audio {
      background: #e0f2fe;
      color: #0284c7;
    }
    .tag-midi {
      background: #ede9fe;
      color: #7c3aed;
    }
    .flow-zone {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 8px;
      margin: 10px 0;
      min-height: 120px;
    }
    .channel-cable {
      width: 100%;
      height: 38px;
      background: #f1f5f9;
      border-radius: 8px;
      border: 1px dashed #cbd5e1;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      overflow: hidden;
    }
    /* Audio Wave Canvas */
    .wave-svg {
      width: 100%;
      height: 100%;
    }
    .wave-path {
      fill: none;
      stroke: #0284c7;
      stroke-width: 2.5;
      stroke-linecap: round;
      transition: stroke-dashoffset 0.1s linear;
    }
    /* MIDI Packet */
    .midi-packet {
      background: #7c3aed;
      color: #ffffff;
      font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
      font-size: 11px;
      font-weight: 600;
      padding: 4px 8px;
      border-radius: 6px;
      box-shadow: 0 2px 5px rgba(124, 58, 237, 0.3);
      position: absolute;
      transform: translateX(-120%);
      white-space: nowrap;
      transition: transform 0.6s cubic-bezier(0.2, 0.8, 0.2, 1);
    }
    .midi-packet.pulse {
      transform: translateX(0%);
    }
    .device-row {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
    }
    .device-box {
      display: flex;
      align-items: center;
      gap: 6px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 6px;
      padding: 4px 8px;
    }
    .device-box.active {
      border-color: #2563eb;
      background: #eff6ff;
      color: #1e2945;
    }
    .footer-desc {
      background: #f8fafc;
      border-radius: 6px;
      padding: 6px 8px;
      font-size: 12px;
      font-weight: 600;
      text-align: center;
    }
    .desc-audio {
      color: #0369a1;
      border: 1px solid #bae6fd;
    }
    .desc-midi {
      color: #6d28d9;
      border: 1px solid #ddd6fe;
    }
    .speaker-icon, .synth-icon {
      font-size: 16px;
      transition: transform 0.2s ease;
    }
    .vibrate {
      transform: scale(1.2);
    }
  </style>
</head>
<body>

  <div class="header">
    <span style="font-size: 13px; font-weight: 700; color: #64748b;">SIGNAL COMPARISON</span>
    <button id="triggerBtn" class="trigger-btn" onclick="triggerPlayback()">
      <span>Strike C4 Key</span>
      <span>🎹</span>
    </button>
  </div>

  <div class="grid">
    
    <div class="panel">
      <div class="panel-title">
        <span>Audio Signal</span>
        <span class="tag tag-audio">Continuous</span>
      </div>

      <div class="flow-zone">
        <div class="device-row">
          <div class="device-box" id="audioSrcBox">
            <span>Mic / Jack</span>
          </div>
          <span style="color:#94a3b8; font-size:14px;">➔</span>
          <div class="device-box" id="audioDstBox">
            <span id="speakerIcon" class="speaker-icon">🔊</span>
            <span>Speaker</span>
          </div>
        </div>

        <div class="channel-cable">
          <svg class="wave-svg" viewBox="0 0 200 40" preserveAspectRatio="none">
            <path id="wavePath" class="wave-path" d="M 0,20 Q 25,20 50,20 T 100,20 T 150,20 T 200,20" />
          </svg>
        </div>
      </div>

      <div class="footer-desc desc-audio">
        Carries sound & voltage
      </div>
    </div>

    
    <div class="panel">
      <div class="panel-title">
        <span>MIDI Data</span>
        <span class="tag tag-midi">Digital</span>
      </div>

      <div class="flow-zone">
        <div class="device-row">
          <div class="device-box" id="midiSrcBox">
            <span>Keyboard</span>
          </div>
          <span style="color:#94a3b8; font-size:14px;">➔</span>
          <div class="device-box" id="midiDstBox">
            <span id="synthIcon" class="synth-icon">🎛️</span>
            <span>Synth Module</span>
          </div>
        </div>

        <div class="channel-cable">
          <div id="midiPacket" class="midi-packet">[ Note: C4 | Vel: 100 | Ch: 1 ]</div>
        </div>
      </div>

      <div class="footer-desc desc-midi">
        Performance instructions (NO sound)
      </div>
    </div>
  </div>

  <script>
    let audioCtx = null;
    let waveOffset = 0;
    let waveActive = false;
    let animId = null;

    function renderWave(amplitude) {
      const path = document.getElementById('wavePath');
      let d = "M 0,20";
      for (let x = 0; x <= 200; x += 10) {
        const y = 20 + Math.sin((x + waveOffset) * 0.15) * amplitude;
        d += ` L ${x},${y.toFixed(1)}`;
      }
      path.setAttribute('d', d);
    }

    function animateWave() {
      if (waveActive) {
        waveOffset += 4;
        renderWave(12);
        animId = requestAnimationFrame(animateWave);
      } else {
        renderWave(0);
      }
    }

    function playTone(freq = 261.63, duration = 0.5) {
      if (!audioCtx) {
        audioCtx = new (window.AudioContext || window.webkitAudioContext)();
      }
      if (audioCtx.state === 'suspended') {
        audioCtx.resume();
      }
      const osc = audioCtx.createOscillator();
      const gain = audioCtx.createGain();
      
      osc.type = 'triangle';
      osc.frequency.setValueAtTime(freq, audioCtx.currentTime);
      
      gain.gain.setValueAtTime(0.2, audioCtx.currentTime);
      gain.gain.exponentialRampToValueAtTime(0.001, audioCtx.currentTime + duration);
      
      osc.connect(gain);
      gain.connect(audioCtx.destination);
      
      osc.start();
      osc.stop(audioCtx.currentTime + duration);
    }

    function triggerPlayback() {
      playTone(261.63, 0.6);

      // Visual: Audio Wave
      waveActive = true;
      cancelAnimationFrame(animId);
      animateWave();
      
      const speaker = document.getElementById('speakerIcon');
      const audioDst = document.getElementById('audioDstBox');
      speaker.classList.add('vibrate');
      audioDst.classList.add('active');

      // Visual: MIDI Packet
      const packet = document.getElementById('midiPacket');
      const synth = document.getElementById('synthIcon');
      const midiDst = document.getElementById('midiDstBox');
      
      packet.classList.remove('pulse');
      void packet.offsetWidth; // force reflow
      packet.classList.add('pulse');
      midiDst.classList.add('active');
      synth.classList.add('vibrate');

      setTimeout(() => {
        waveActive = false;
        renderWave(0);
        speaker.classList.remove('vibrate');
        audioDst.classList.remove('active');
        synth.classList.remove('vibrate');
        midiDst.classList.remove('active');
      }, 650);
    }

    // Initial flat wave render
    renderWave(0);
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>MIDI Byte Structure</title>
  <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;
      padding: 8px 10px;
      display: flex;
      flex-direction: column;
      gap: 10px;
    }

    .byte-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px 10px;
      display: flex;
      flex-direction: column;
      gap: 6px;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.03);
    }

    .header-row {
      display: flex;
      justify-content: space-between;
      align-items: center;
      flex-wrap: wrap;
      gap: 4px;
    }

    .byte-title {
      font-size: 13px;
      font-weight: 700;
      display: flex;
      align-items: center;
      gap: 6px;
      color: #0f172a;
    }

    .badge {
      font-size: 10px;
      font-weight: 700;
      padding: 1px 6px;
      border-radius: 10px;
      letter-spacing: 0.2px;
    }

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

    .badge-data {
      background: #ecfdf5;
      color: #059669;
      border: 1px solid #a7f3d0;
    }

    .summary-text {
      font-size: 11px;
      color: #475569;
      font-weight: 600;
    }

    .byte-grid {
      display: grid;
      grid-template-columns: repeat(8, minmax(0, 1fr));
      gap: 4px;
      width: 100%;
    }

    .bit-box {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 4px 1px;
      border-radius: 6px;
      text-align: center;
      user-select: none;
      min-width: 0;
    }

    .bit-num {
      font-size: 8.5px;
      font-weight: 600;
      opacity: 0.8;
      margin-bottom: 2px;
      line-height: 1;
      white-space: nowrap;
    }

    .bit-val {
      font-size: 15px;
      font-weight: 800;
      line-height: 1.1;
    }

    /* Status byte color themes */
    .msb-status {
      background: #2563eb;
      color: #ffffff;
      border: 1px solid #1d4ed8;
    }

    .cmd-bits {
      background: #eff6ff;
      color: #1d4ed8;
      border: 1px solid #bfdbfe;
    }

    .chan-bits {
      background: #f5f3ff;
      color: #6d28d9;
      border: 1px solid #ddd6fe;
    }

    /* Data byte color themes */
    .msb-data {
      background: #059669;
      color: #ffffff;
      border: 1px solid #047857;
    }

    .val-bits {
      background: #ecfdf5;
      color: #047857;
      border: 1px solid #a7f3d0;
    }

    .group-labels {
      display: grid;
      grid-template-columns: 1fr 3fr 4fr;
      gap: 4px;
      text-align: center;
      width: 100%;
    }

    .data-group-labels {
      display: grid;
      grid-template-columns: 1fr 7fr;
      gap: 4px;
      text-align: center;
      width: 100%;
    }

    .label-tag {
      padding: 2px 2px;
      border-radius: 4px;
      font-size: 10px;
      font-weight: 700;
      white-space: nowrap;
      overflow: hidden;
      text-overflow: ellipsis;
      display: flex;
      align-items: center;
      justify-content: center;
      min-width: 0;
    }

    .tag-msb-status { background: #dbeafe; color: #1e40af; }
    .tag-cmd { background: #e0e7ff; color: #3730a3; }
    .tag-chan { background: #ede9fe; color: #5b21b6; }

    .tag-msb-data { background: #d1fae5; color: #065f46; }
    .tag-val { background: #d1fae5; color: #047857; }

    .interactive-panel {
      display: flex;
      justify-content: space-between;
      align-items: center;
      flex-wrap: wrap;
      gap: 6px;
      padding: 6px 8px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
    }

    .preset-btns {
      display: flex;
      flex-wrap: wrap;
      gap: 4px;
    }

    .btn {
      background: #ffffff;
      border: 1px solid #cbd5e1;
      color: #1e2945;
      padding: 4px 8px;
      font-size: 11px;
      font-weight: 600;
      border-radius: 5px;
      cursor: pointer;
      box-shadow: 0 1px 2px rgba(0, 0, 0, 0.04);
      transition: background-color 0.15s ease, color 0.15s ease, border-color 0.15s ease;
    }

    .btn:hover {
      background-color: #f1f5f9;
    }

    .btn.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
    }

    .btn.active:hover {
      background: #1d4ed8;
    }

    .info-readout {
      font-size: 11.5px;
      font-weight: 600;
      color: #334155;
    }

    @media (max-width: 400px) {
      body {
        padding: 6px;
        gap: 8px;
      }
      .byte-card {
        padding: 6px 8px;
        gap: 5px;
      }
      .label-tag {
        font-size: 9px;
      }
      .bit-num {
        font-size: 8px;
      }
      .bit-val {
        font-size: 13px;
      }
      .byte-title {
        font-size: 12px;
      }
      .summary-text {
        font-size: 10px;
      }
      .btn {
        font-size: 10px;
        padding: 3px 6px;
      }
      .info-readout {
        font-size: 10.5px;
      }
    }
  </style>
</head>
<body>

  
  <div class="byte-card">
    <div class="header-row">
      <div class="byte-title">
        <span>Status Byte</span>
        <span class="badge badge-status">128–255</span>
      </div>
      <div class="summary-text" id="statusDesc">MSB = 1 → Command &amp; Channel</div>
    </div>

    <div class="byte-grid" id="statusGrid">
      <div class="bit-box msb-status"><span class="bit-num">7 (MSB)</span><span class="bit-val" id="s7">1</span></div>
      <div class="bit-box cmd-bits"><span class="bit-num">6</span><span class="bit-val" id="s6">0</span></div>
      <div class="bit-box cmd-bits"><span class="bit-num">5</span><span class="bit-val" id="s5">0</span></div>
      <div class="bit-box cmd-bits"><span class="bit-num">4</span><span class="bit-val" id="s4">1</span></div>
      <div class="bit-box chan-bits"><span class="bit-num">3</span><span class="bit-val" id="s3">0</span></div>
      <div class="bit-box chan-bits"><span class="bit-num">2</span><span class="bit-val" id="s2">0</span></div>
      <div class="bit-box chan-bits"><span class="bit-num">1</span><span class="bit-val" id="s1">0</span></div>
      <div class="bit-box chan-bits"><span class="bit-num">0</span><span class="bit-val" id="s0">0</span></div>
    </div>

    <div class="group-labels">
      <div class="label-tag tag-msb-status" title="Most Significant Bit">MSB</div>
      <div class="label-tag tag-cmd" id="cmdLabel">Type (3 bits)</div>
      <div class="label-tag tag-chan" id="chanLabel">Channel (4 bits)</div>
    </div>
  </div>

  
  <div class="byte-card">
    <div class="header-row">
      <div class="byte-title">
        <span>Data Byte</span>
        <span class="badge badge-data">0–127</span>
      </div>
      <div class="summary-text" id="dataDesc">MSB = 0 → Pitch, Velocity, or CC</div>
    </div>

    <div class="byte-grid" id="dataGrid">
      <div class="bit-box msb-data"><span class="bit-num">7 (MSB)</span><span class="bit-val" id="d7">0</span></div>
      <div class="bit-box val-bits"><span class="bit-num">6</span><span class="bit-val" id="d6">0</span></div>
      <div class="bit-box val-bits"><span class="bit-num">5</span><span class="bit-val" id="d5">1</span></div>
      <div class="bit-box val-bits"><span class="bit-num">4</span><span class="bit-val" id="d4">1</span></div>
      <div class="bit-box val-bits"><span class="bit-num">3</span><span class="bit-val" id="d3">1</span></div>
      <div class="bit-box val-bits"><span class="bit-num">2</span><span class="bit-val" id="d2">1</span></div>
      <div class="bit-box val-bits"><span class="bit-num">1</span><span class="bit-val" id="d1">0</span></div>
      <div class="bit-box val-bits"><span class="bit-num">0</span><span class="bit-val" id="d0">0</span></div>
    </div>

    <div class="data-group-labels">
      <div class="label-tag tag-msb-data" title="Most Significant Bit">MSB</div>
      <div class="label-tag tag-val" id="valLabel">Value (7 bits: 0000000 to 1111111)</div>
    </div>
  </div>

  
  <div class="interactive-panel">
    <div class="preset-btns">
      <button class="btn active" onclick="setExample(0)">Note On (60)</button>
      <button class="btn" onclick="setExample(1)">Max Velocity (127)</button>
      <button class="btn" onclick="setExample(2)">Pitch Bend</button>
    </div>
    <div class="info-readout" id="readout">Note On · Ch 1 · Pitch 60 (Middle C)</div>
  </div>

  <script>
    const presets = [
      {
        statusBits: [1, 0, 0, 1, 0, 0, 0, 0], // Note On (1001), Ch 1 (0000)
        dataBits:   [0, 0, 1, 1, 1, 1, 0, 0], // 60 (Middle C)
        cmd: 'Note On (1001)',
        chan: 'Channel 1 (0000)',
        val: 'Middle C = 60 (0111100)',
        readout: 'Note On · Ch 1 · Pitch 60 (Middle C)'
      },
      {
        statusBits: [1, 0, 0, 1, 0, 0, 0, 0], // Note On, Ch 1
        dataBits:   [0, 1, 1, 1, 1, 1, 1, 1], // 127 Max
        cmd: 'Note On (1001)',
        chan: 'Channel 1 (0000)',
        val: 'Max Velocity = 127 (1111111)',
        readout: 'Velocity · Value 127 (Fortissimo)'
      },
      {
        statusBits: [1, 1, 1, 0, 0, 0, 0, 1], // Pitch Bend (1110), Ch 2 (0001)
        dataBits:   [0, 1, 0, 0, 0, 0, 0, 0], // 64 Center
        cmd: 'Pitch Bend (1110)',
        chan: 'Channel 2 (0001)',
        val: 'Center = 64 (1000000)',
        readout: 'Pitch Bend · Ch 2 · Value 64 (Center)'
      }
    ];

    function setExample(idx) {
      const p = presets[idx];
      const btns = document.querySelectorAll('.btn');
      btns.forEach((b, i) => b.classList.toggle('active', i === idx));

      // Update status bits
      for (let i = 0; i < 8; i++) {
        document.getElementById('s' + (7 - i)).textContent = p.statusBits[i];
      }

      // Update data bits
      for (let i = 0; i < 8; i++) {
        document.getElementById('d' + (7 - i)).textContent = p.dataBits[i];
      }

      document.getElementById('cmdLabel').textContent = p.cmd;
      document.getElementById('chanLabel').textContent = p.chan;
      document.getElementById('valLabel').textContent = p.val;
      document.getElementById('readout').textContent = p.readout;
    }
  </script>
</body>
</html>

MUSTECH-24.4

Aligned learning resources

Related diagrams