Javascript Piano Keyboard

 <div class="container">
        <div class="header">
            <h1>🎹 Piano Keyboard</h1>
            <p class="subtitle">Play with your mouse, touch, or keyboard</p>
        </div>

        <div class="piano-content">
            <div class="controls">
                <div class="control-group">
                    <label for="waveform">Waveform:</label>
                    <select id="waveform">
                        <option value="sine">Sine</option>
                        <option value="square">Square</option>
                        <option value="sawtooth">Sawtooth</option>
                        <option value="triangle">Triangle</option>
                    </select>
                </div>
                <div class="control-group">
                    <label for="volume">Volume:</label>
                    <input type="range" id="volume" min="0" max="1" step="0.1" value="0.3">
                </div>
            </div>

            <div class="piano-container">
                <div class="piano" id="piano"></div>
            </div>

            <div class="note-display">
                <span id="currentNote">Click or press a key to play</span>
            </div>

            <div class="instructions">
                Use keys: A S D F G H J K L ; ' for white keys | W E T Y U O P for black keys
            </div>
        </div>
    </div>

      * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%);
            padding: 20px;
            min-height: 100vh;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .container {
            background: white;
            border-radius: 16px;
            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
            overflow: hidden;
            max-width: 1400px;
            width: 100%;
        }

        .header {
            background: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%);
            color: white;
            padding: 30px;
            text-align: center;
        }

        h1 {
            font-size: 32px;
            margin-bottom: 8px;
        }

        .subtitle {
            font-size: 14px;
            opacity: 0.9;
        }

        .piano-content {
            padding: 40px 30px;
        }

        .controls {
            display: flex;
            justify-content: center;
            gap: 20px;
            margin-bottom: 30px;
            flex-wrap: wrap;
        }

        .control-group {
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .control-group label {
            font-size: 14px;
            color: #666;
            font-weight: 500;
        }

        .control-group select,
        .control-group input {
            padding: 8px 12px;
            border: 2px solid #e0e0e0;
            border-radius: 6px;
            font-size: 14px;
            cursor: pointer;
            transition: border-color 0.3s;
        }

        .control-group input {
            width: 80px;
        }

        .control-group select:focus,
        .control-group input:focus {
            outline: none;
            border-color: #43e97b;
        }

        .piano-container {
            position: relative;
            display: flex;
            justify-content: center;
            margin: 0 auto;
            max-width: 1200px;
            height: 300px;
            background: #1a1a1a;
            padding: 20px;
            border-radius: 12px;
            box-shadow: inset 0 4px 12px rgba(0, 0, 0, 0.5);
        }

        .piano {
            position: relative;
            display: flex;
            height: 100%;
        }

        .key {
            position: relative;
            cursor: pointer;
            user-select: none;
            transition: all 0.05s;
        }

        .white-key {
            width: 60px;
            height: 100%;
            background: linear-gradient(to bottom, #ffffff 0%, #f5f5f5 100%);
            border: 2px solid #333;
            border-radius: 0 0 8px 8px;
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
        }

        .white-key:hover {
            background: linear-gradient(to bottom, #f0f0f0 0%, #e0e0e0 100%);
        }

        .white-key:active,
        .white-key.active {
            background: linear-gradient(to bottom, #43e97b 0%, #38f9d7 100%);
            transform: translateY(2px);
            box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
        }

        .black-key {
            position: absolute;
            width: 40px;
            height: 60%;
            background: linear-gradient(to bottom, #2a2a2a 0%, #000000 100%);
            border: 2px solid #000;
            border-radius: 0 0 6px 6px;
            z-index: 10;
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.5);
        }

        .black-key:hover {
            background: linear-gradient(to bottom, #3a3a3a 0%, #1a1a1a 100%);
        }

        .black-key:active,
        .black-key.active {
            background: linear-gradient(to bottom, #43e97b 0%, #38f9d7 100%);
            transform: translateY(2px);
            box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
        }

        .key-label {
            position: absolute;
            bottom: 10px;
            left: 50%;
            transform: translateX(-50%);
            font-size: 11px;
            font-weight: 600;
            color: #666;
            background: rgba(255, 255, 255, 0.8);
            padding: 2px 6px;
            border-radius: 3px;
        }

        .black-key .key-label {
            color: #fff;
            background: rgba(0, 0, 0, 0.5);
        }

        .note-display {
            text-align: center;
            margin-top: 30px;
            font-size: 18px;
            color: #666;
            min-height: 30px;
        }

        .note-name {
            font-weight: 600;
            color: #43e97b;
            font-size: 24px;
        }

        .instructions {
            text-align: center;
            margin-top: 20px;
            color: #999;
            font-size: 13px;
        }

        @media (max-width: 768px) {
            .white-key {
                width: 45px;
            }

            .black-key {
                width: 30px;
            }

            .piano-container {
                height: 250px;
            }
        }

const audioContext = new (window.AudioContext || window.webkitAudioContext)();
const masterGain = audioContext.createGain();
masterGain.connect(audioContext.destination);

let activeNotes = new Map();
let sustainPedal = false;
let sustainedNotes = new Set();

const notes = [
  { note: 'C4', freq: 261.63, white: true, key: 'A' },
  { note: 'C#4', freq: 277.18, white: false, key: 'W' },
  { note: 'D4', freq: 293.66, white: true, key: 'S' },
  { note: 'D#4', freq: 311.13, white: false, key: 'E' },
  { note: 'E4', freq: 329.63, white: true, key: 'D' },
  { note: 'F4', freq: 349.23, white: true, key: 'F' },
  { note: 'F#4', freq: 369.99, white: false, key: 'T' },
  { note: 'G4', freq: 392.00, white: true, key: 'G' },
  { note: 'G#4', freq: 415.30, white: false, key: 'Y' },
  { note: 'A4', freq: 440.00, white: true, key: 'H' },
  { note: 'A#4', freq: 466.16, white: false, key: 'U' },
  { note: 'B4', freq: 493.88, white: true, key: 'J' },
  { note: 'C5', freq: 523.25, white: true, key: 'K' },
  { note: 'C#5', freq: 554.37, white: false, key: 'O' },
  { note: 'D5', freq: 587.33, white: true, key: 'L' },
  { note: 'D#5', freq: 622.25, white: false, key: 'P' },
  { note: 'E5', freq: 659.25, white: true, key: ';' },
  { note: 'F5', freq: 698.46, white: true, key: '\'' }
];

function createPiano() {
  const piano = document.getElementById('piano');
  let whiteKeyIndex = 0;

  notes.forEach((noteData, index) => {
    const key = document.createElement('div');
    key.className = noteData.white ? 'white-key key' : 'black-key key';
    key.dataset.note = noteData.note;
    key.dataset.freq = noteData.freq;
    key.dataset.key = noteData.key;

    const label = document.createElement('div');
    label.className = 'key-label';
    label.textContent = noteData.key;
    key.appendChild(label);

    if (noteData.white) {
      piano.appendChild(key);
      whiteKeyIndex++;
    } else {
      key.style.left = `${(whiteKeyIndex * 60) - 20}px`;
      piano.appendChild(key);
    }

    key.addEventListener('mousedown', () => playNote(noteData.freq, noteData.note, key));
    key.addEventListener('mouseup', () => stopNote(noteData.note, key));
    key.addEventListener('mouseleave', () => {
      if (activeNotes.has(noteData.note)) {
        stopNote(noteData.note, key);
      }
    });
    key.addEventListener('touchstart', (e) => {
      e.preventDefault();
      playNote(noteData.freq, noteData.note, key);
    });
    key.addEventListener('touchend', (e) => {
      e.preventDefault();
      stopNote(noteData.note, key);
    });
  });
}

function playNote(frequency, noteName, keyElement) {
  if (activeNotes.has(noteName)) return;

  const now = audioContext.currentTime;
  const volume = parseFloat(document.getElementById('volume').value);
  const waveform = document.getElementById('waveform').value;

  // Create oscillator
  const oscillator = audioContext.createOscillator();
  oscillator.type = waveform;
  oscillator.frequency.setValueAtTime(frequency, now);

  // Create gain envelope for ADSR
  const gainNode = audioContext.createGain();
  gainNode.gain.setValueAtTime(0, now);

  // Attack (0.01s)
  gainNode.gain.linearRampToValueAtTime(volume, now + 0.01);

  // Decay to sustain level (0.1s)
  gainNode.gain.linearRampToValueAtTime(volume * 0.7, now + 0.11);

  oscillator.connect(gainNode);
  gainNode.connect(masterGain);

  oscillator.start(now);

  activeNotes.set(noteName, { oscillator, gainNode, keyElement });

  if (keyElement) {
    keyElement.classList.add('active');
  }

  updateDisplay();
}

function stopNote(noteName, keyElement) {
  if (!activeNotes.has(noteName)) return;

  const noteData = activeNotes.get(noteName);

  if (sustainPedal) {
    sustainedNotes.add(noteName);
    return;
  }

  const now = audioContext.currentTime;

  // Release (fade out over 0.3s for more natural sound)
  noteData.gainNode.gain.cancelScheduledValues(now);
  noteData.gainNode.gain.setValueAtTime(noteData.gainNode.gain.value, now);
  noteData.gainNode.gain.exponentialRampToValueAtTime(0.001, now + 0.3);

  noteData.oscillator.stop(now + 0.3);

  activeNotes.delete(noteName);

  if (keyElement) {
    keyElement.classList.remove('active');
  }

  updateDisplay();
}

function updateDisplay() {
  const activeNoteNames = Array.from(activeNotes.keys());
  const display = document.getElementById('currentNote');

  if (activeNoteNames.length === 0) {
    display.innerHTML = 'Click or press a key to play';
  } else {
    display.innerHTML = `Playing: <span class="note-name">${activeNoteNames.join(', ')}</span>`;
  }
}

function releaseSustainedNotes() {
  sustainedNotes.forEach(noteName => {
    if (activeNotes.has(noteName)) {
      const noteData = activeNotes.get(noteName);
      const now = audioContext.currentTime;

      noteData.gainNode.gain.cancelScheduledValues(now);
      noteData.gainNode.gain.setValueAtTime(noteData.gainNode.gain.value, now);
      noteData.gainNode.gain.exponentialRampToValueAtTime(0.001, now + 0.3);

      noteData.oscillator.stop(now + 0.3);

      activeNotes.delete(noteName);

      if (noteData.keyElement) {
        noteData.keyElement.classList.remove('active');
      }
    }
  });
  sustainedNotes.clear();
  updateDisplay();
}

document.addEventListener('keydown', (e) => {
  // Sustain pedal (space bar)
  if (e.code === 'Space' && !e.repeat) {
    e.preventDefault();
    sustainPedal = true;
    return;
  }

  const key = e.key.toUpperCase();
  const noteData = notes.find(n => n.key === key);

  if (noteData && !e.repeat) {
    const keyElement = document.querySelector(`[data-key="${key}"]`);
    playNote(noteData.freq, noteData.note, keyElement);
  }
});

document.addEventListener('keyup', (e) => {
  // Sustain pedal release
  if (e.code === 'Space') {
    e.preventDefault();
    sustainPedal = false;
    releaseSustainedNotes();
    return;
  }

  const key = e.key.toUpperCase();
  const noteData = notes.find(n => n.key === key);

  if (noteData) {
    const keyElement = document.querySelector(`[data-key="${key}"]`);
    stopNote(noteData.note, keyElement);
  }
});

createPiano();