The user wants me to build a playable piano keyboard web app using Tone.js (pre-provided tone.min.js). Let me first check what's in the current directory.

The user wants me to build a playable piano keyboard web app using Tone.js (loaded from tone.min.js). Let me check what's in the tone.min.js file briefly to understand what API is available, then build the app.

Let me build a self-contained index.html with:
1. A piano keyboard UI (mouse click + computer keyboard)
2. ADSR envelope synthesis using Tone.js
3. Visual key feedback

Let me build this. I'll use Tone.js Synth with an ADSR envelope. The keyboard will span one or two octaves, with white and black keys.

Computer keyboard mapping: I'll use a common mapping like:
- Lower row: A=S, W=E, S=F, T=G, D=A, J=B, K=C#, L=D, U=E (white keys)
- Or a simpler mapping

Let me design a nice looking piano with proper black/white key layout.

Standard piano octave (C4 to B4 as example):
- White keys: C, D, E, F, G, A, B
- Black keys: C#, D#, F#, G#, A#

Computer keyboard mapping (two octaves C4-B5):
Row 1 (QWERTY): W=E, E=F, R=G, T=A, Y=B (wait, that doesn't align well)

Let me use a standard mapping:
- A = C, W = C#, S = D, E = D#, D = E, F = F, T = F#, G = G, Y = G#, H = A, U = A#, J = B
- Then Z = C (next octave), X = C#, C = D, V = D#, B = E, N = F, M = F#

Actually let me use a simpler 1-octave mapping with shift for upper octave.

Common VST-style mapping:
- Z = C3, S = C#3, X = D3, D = D#3, C = E3, V = F3, G = F#3, B = G3, H = G#3, N = A3, J = A#3, M = B3
- Then Q = C4, 2 = C#4, W = D4, 3 = D#4, E = E4, R = F4, 5 = F#4, T = G4, 6 = G#4, Y = A4, 7 = A#4, U = B4

That's complex. Let me use something more intuitive for a single octave C4-B4:

White keys: A C D F G H J K L (7 white keys for one octave: C D E F G A B)
Wait, that's 7 white keys. Let me use: A=C, S=D, D=E, F=F, G=G, H=A, J=B (7 keys)

Black keys: W=C#, E=D#, T=F#, Y=G#, U=A# (5 black keys)

For upper octave, use shift + same keys or use lower row.

Actually let me do two octaves for better playability:
- Octave 4 (C4-B4): A=C4, W=C#4, S=D4, E=D#4, D=E4, F=F4, T=F#4, G=G4, Y=G#4, H=A4, U=A#4, J=B4
- Octave 5 (C5-B5): Z=C5, X=C#5, C=D5, V=D#5, B=E5, N=F5, M=F#5... wait that's only 7 white keys but I need to map black keys too.

Let me simplify: Use the lower letter row for white keys of octave 4, upper letter row with shift for octave 5, and number row for black keys. Actually this gets confusing.

Simplest approach: Use two rows of keys for two octaves.

Row 1 (home row, lower): A=C4, S=D4, D=E4, F=F4, G=G4, H=A4, J=B4 (white keys, 7)
Row 1 black keys (above): W=C#4, E=D#4, T=F#4, Y=G#4, U=A#4 (5 black keys)
Row 2 (lower): Z=C5, X=D5, C=E5, V=F5, B=G5, N=A5, M=B5 (white keys, 7)
Row 2 black keys (above): S... no wait, S is used for D4.

Let me use a different approach. Use keyboard rows:

Lower octave (C4-B4):
- White: A, S, D, F, G, H, J (C, D, E, F, G, A, B)
- Black: W, E, T, Y, U (C#, D#, F#, G#, A#)
  - W is above A (C), E is above S (D), T is above D... wait T is above G not F.

Hmm, let me think of a common piano keyboard mapping used in web synths.

A popular mapping (from many web piano tutorials):
- White keys: A, S, D, F, G, H, J, K (two octaves worth)

Let me just use one octave (C4-B4) with:
- White keys: A=C4, S=D4, D=E4, F=F4, G=G4, H=A4, J=B4
- Black keys: W=C#4, E=D#4, T=F#4, Y=G#4, U=A#4

And for upper octave (C5-B5) with Shift held:
- or use Z=C5, X=D5, C=E5, V=F5, B=G5, N=A5, M=B5
- and S... no S is used.

Actually, let me use the number row + letter row combination:

Octave 4 (C4-B4):
- White: A, S, D, F, G, H, J
- Black: W, E, T, Y, U

Octave 5 (C5-B5):
- White: Z, X, C, V, B, N, M
- Black: (need 5 keys) - use Shift+... or use the keys above Z row which are Q, 2, W, 3, E... but those overlap.

This is getting complicated. Let me just use a simple two-octave mapping that's documented:

Standard "computer keyboard piano" mapping (two octaves C4-C6):
- C4: A
- C#4: W
- D4: S
- D#4: E
- E4: D
- F4: F
- F#4: T
- G4: G
- G#4: Y
- A4: H
- A#4: U
- B4: J
- C5: Z
- C#5: X
- D5: C
- D#5: V
- E5: B
- F5: N
- F#5: M
- G5: , (comma)
- G#5: L
- A5: .
- A#5: ;
- B5: /

Hmm. Let me simplify further and just do one octave that's clearly labeled, plus a second octave on the row below.

Actually, I'll just implement a clean design. Let me use:

Octave 4: A=C4, S=D4, D=E4, F=F4, G=G4, H=A4, J=B4 (white)
           W=C#4, E=D#4, T=F#4, Y=G#4, U=A#4 (black)

Octave 5: Z=C5, X=D5, C=E5, V=F5, B=G5, N=A5, M=B5 (white)  
           (black keys for octave 5 using the same physical keys as octave 4 black keys? No, that doesn't work)

Let me use a commonly used mapping from web audio piano tutorials. I'll go with:

**Octave 4** (C4-B4):
- White: A, S, D, F, G, H, J
- Black: W, E, T, Y, U

**Octave 5** (C5-B5):
- White: Z, X, C, V, B, N, M
- Black: (use Shift + the octave 4 black keys? Or use a separate row)

For octave 5 black keys I'll use: (Shift+2)=C#5, (Shift+3)=D#5, (Shift+5)=F#5, (Shift+6)=G#5, (Shift+7)=A#5

That uses the number row. Actually this is getting overly complex. Let me use a simpler approach:

I'll use the row above for black keys of both octaves:
- Octave 4 black: W, E, T, Y, U
- Octave 5 black: 2, 3, 5, 6, 7 (no shift needed, just number keys)

Wait, that's a nice mapping! Let me finalize:

**Octave 4** (C4-B4):
- White keys: A=C4, S=D4, D=E4, F=F4, G=G4, H=A4, J=B4
- Black keys: W=C#4, E=D#4, T=F#4, Y=G#4, U=A#4

**Octave 5** (C5-B5):
- White keys: Z=C5, X=D5, C=E5, V=F5, B=G5, N=A5, M=B5
- Black keys: 2=C#5, 3=D#5, 5=F#5, 6=G#5, 7=A#5

This is clean and intuitive! The white keys are on the two main rows, and black keys are above (row above A for octave 4, number row for octave 5).

Now let me build the HTML.

For Tone.js, I'll use a PolySynth with a Synth voice that has an ADSR envelope. Or I can use a simple Synth with envelope.

Let me use Tone.Synth with envelope: {
  attack: 0.005,
  decay: 0.1,
  sustain: 0.3,
  release: 0.5
}

Or Tone.FMSynth, Tone.AMSynth for different tones. Let me use a basic Synth with a nice ADSR.

Actually, for a piano-like sound, I could use Tone.PluckSynth or just a regular Synth with a piano-like envelope. Let me use a simple Synth with ADSR controls.

I'll also add ADSR controls (sliders) for the user to tweak the envelope.

Let me design:
1. ADSR sliders (attack, decay, sustain, release)
2. Piano keyboard (2 octaves, C4-B5)
3. Computer keyboard support
4. Mouse click support
5. Visual key press feedback

For the UI, I'll make it look like a real piano with:
- White keys as rectangular blocks
- Black keys as shorter, elevated blocks
- Keys light up / change color when pressed
- Note labels on keys

Let me write the code.

For the keyboard rendering, I'll use a flex layout where black keys are positioned over white keys. The standard approach:
- Each octave has 7 white keys and 5 black keys
- Black keys are positioned at specific offsets

The CSS for piano layout typically uses absolute positioning for black keys over white keys.

Let me calculate positions:
- White keys: 7 per octave, each 1 unit wide
- Black keys: positioned between certain white keys
  - C# is between C and D (at 0.75 units from C's left edge, or 0.5 + half of the gap)
  - D# is between D and E
  - F# is between F and G
  - G# is between G and A
  - A# is between A and B

With white key width = W, black key width = ~0.6W, black key positioned at W - blackWidth/2 from the left of the preceding white key (for C#), or simply centered on the boundary between white keys.

Standard approach: black key at position (whiteKeyIndex + 1) * whiteKeyWidth - blackKeyWidth/2 for the gap between white key i and i+1.

Let me use this layout approach with CSS. I'll position black keys absolutely.

Actually let me use a JS-generated layout where I compute positions.

Let me write the full HTML now.

I'll use:
- Tone.start() on user gesture (click on the piano or a start button)
- A "Start Audio" button since browsers require user gesture
- ADSR sliders
- Piano keyboard

Let me also add a nice visual design with gradients, shadows, and smooth animations.

Here's my plan for the HTML file:

```html
<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Piano Synthesizer</title>
  <style>
    /* CSS here */

  </style>
</head>
<body>
  <!-- UI -->
  <script src="tone.min.js"></script>
  <script>
    // JS here
  </script>
</body>
</html>

```

Let me write the full implementation.

For keys, I'll render white keys as divs in a flex row, and black keys as absolutely positioned divs overlaid on top.

Let me calculate the positions properly.

White key width: let's say 60px
Black key width: 36px
Black key height: 60% of white key height

In an octave (7 white keys, 5 black keys):
- White key positions: index * whiteWidth
- Black key positions (center x):
  - C#: 1 * whiteWidth - blackWidth/2 (between C and D, centered on the boundary)
  - D#: 2 * whiteWidth - blackWidth/2
  - F#: 4 * whiteWidth - blackWidth/2
  - G#: 5 * whiteWidth - blackWidth/2
  - A#: 6 * whiteWidth - blackWidth/2

Wait, let me reconsider. The boundary between C and D is at x = 1 * whiteWidth. The black key C# sits centered on this boundary, so its left edge is at 1 * whiteWidth - blackWidth/2.

Similarly:
- D# sits between D (index 1) and E (index 2), so left edge at 2 * whiteWidth - blackWidth/2
- F# sits between F (index 3) and G (index 4), so left edge at 4 * whiteWidth - blackWidth/2
- G#: 5 * whiteWidth - blackWidth/2
- A#: 6 * whiteWidth - blackWidth/2

Now for 2 octaves (C4-B5), I'll have 14 white keys and 10 black keys.

Note names and indices:
Octave 4:
- C4: white index 0
- D4: white index 1
- E4: white index 2
- F4: white index 3
- G4: white index 4
- A4: white index 5
- B4: white index 6

Octave 5:
- C5: white index 7
- D5: white index 8
- E5: white index 9
- F5: white index 10
- G5: white index 11
- A5: white index 12
- B5: white index 13

Black keys:
- C#4: between C4 and D4, so at white index 0→1 boundary, pos = 1 * whiteWidth - blackWidth/2
- D#4: between D4 and E4, pos = 2 * whiteWidth - blackWidth/2
- F#4: between F4 and G4, pos = 4 * whiteWidth - blackWidth/2
- G#4: between G4 and A4, pos = 5 * whiteWidth - blackWidth/2
- A#4: between A4 and B4, pos = 6 * whiteWidth - blackWidth/2
- C#5: between C5 and D5, pos = 8 * whiteWidth - blackWidth/2
- D#5: between D5 and E5, pos = 9 * whiteWidth - blackWidth/2
- F#5: between F5 and G5, pos = 11 * whiteWidth - blackWidth/2
- G#5: between G5 and A5, pos = 12 * whiteWidth - blackWidth/2
- A#5: between A5 and B5, pos = 13 * whiteWidth - blackWidth/2

Computer keyboard mapping (as planned):
Octave 4:
- A = C4 (white index 0)
- W = C#4 (black)
- S = D4 (white index 1)
- E = D#4 (black)
- D = E4 (white index 2)
- F = F4 (white index 3)
- T = F#4 (black)
- G = G4 (white index 4)
- Y = G#4 (black)
- H = A4 (white index 5)
- U = A#4 (black)
- J = B4 (white index 6)

Octave 5:
- Z = C5 (white index 7)
- 2 = C#5 (black)
- X = D5 (white index 8)
- 3 = D#5 (black)
- C = E5 (white index 9)
- V = F5 (white index 10)
- 5 = F#5 (black)
- B = G5 (white index 11)
- 6 = G#5 (black)
- N = A5 (white index 12)
- 7 = A#5 (black)
- M = B5 (white index 13)

That's a nice mapping! All keys are covered.

Now let me write the code. I'll use Tone.PolySynth so multiple notes can play simultaneously, with a Synth voice that has the ADSR envelope.

Actually, for individual note control and better visual feedback, I could use multiple Synth instances or a PolySynth. PolySynth is cleaner.

Let me use:
```js
const synth = new Tone.PolySynth(Tone.Synth, {
  oscillator: { type: 'triangle' },
  envelope: {
    attack: 0.005,
    decay: 0.1,
    sustain: 0.3,
    release: 0.5
  }
}).toDestination();
```

Then update envelope when sliders change:
```js
synth.set({ envelope: { attack: attackVal, decay: decayVal, sustain: sustainVal, release: releaseVal } });
```

Wait, with PolySynth, I think you need to set the options on the voice. Let me check... Actually, for PolySynth, you can do:
```js
synth.set({ envelope: { attack: 0.1 } });
```
And it should propagate to all voices. Or you can use:
```js
synth.voices[0].envelope.attack = 0.1;
```

Actually, the recommended way is to set the envelope on the PolySynth's options, which will affect new voices. For existing voices, you might need to set it differently. Let me just use `synth.set()` which should work.

Hmm, actually for Tone.js PolySynth, `set` might not update the envelope of existing voices. Let me create a fresh synth and dispose/replace, or just use individual Synth instances.

For simplicity, let me use a single Synth and handle monophonic or just use PolySynth and accept that envelope changes apply to new notes. Actually, `synth.set()` on a PolySynth does update all voices' envelopes in Tone.js v14+.

Let me just write the code and test mentally.

Actually, in Tone.js, PolySynth.set({envelope: {...}}) sets on the PolySynth options but each voice has its own envelope. To update all voices, you might need to iterate. But in practice, setting on the PolySynth and then triggering notes should use the new settings for new voices. Old voices still play with old envelope until released.

For a simpler approach, let me just use a single Synth (monophonic) or a few Synths. Actually, for a piano, polyphony is important. Let me use PolySynth and update voices properly.

In Tone.js, you can do:
```js
polySynth.voices.forEach(voice => {
  voice.envelope.attack = newValue;
});
```

This should work. Let me use this approach.

Alright, let me write the complete code now.

For the visual design, I'll make:
- Black background for the piano area
- White keys with slight gradient and border
- Black keys with dark gradient
- Pressed keys glow/light up
- Note labels on keys
- ADSR section with labeled sliders
- A status indicator showing which keys are pressed (computer keyboard)
- A "Start Audio" button

Let me also add a nice header/title.

Now coding:

```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Piano Synthesizer</title>
<style>
  * { box-sizing: border-box; margin: 0; padding: 0; }
  
  body {
    font-family: 'Segoe UI', system-ui, sans-serif;
    background: #1a1a2e;
    color: #eee;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 20px;
    user-select: none;
  }
  
  h1 {
    font-size: 2rem;
    margin-bottom: 4px;
    background: linear-gradient(90deg, #f7971e, #ffd200);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
  }
  
  .subtitle {
    color: #888;
    margin-bottom: 20px;
    font-size: 0.9rem;
  }
  
  .controls {
    width: 100%;
    max-width: 900px;
    background: #16213e;
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 20px;
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
    align-items: flex-end;
  }
  
  .control-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
    min-width: 120px;
  }
  
  .control-group label {
    font-size: 0.85rem;
    color: #aaa;
    text-transform: uppercase;
    letter-spacing: 1px;
  }
  
  .control-group .value {
    font-size: 0.8rem;
    color: #ffd200;
    font-family: monospace;
  }
  
  input[type="range"] {
    width: 100%;
    height: 6px;
    -webkit-appearance: none;
    background: #0f3460;
    border-radius: 3px;
    outline: none;
  }
  
  input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: #ffd200;
    cursor: pointer;
  }
  
  .start-btn {
    padding: 10px 24px;
    background: linear-gradient(135deg, #f7971e, #ffd200);
    border: none;
    border-radius: 8px;
    color: #1a1a2e;
    font-weight: bold;
    font-size: 1rem;
    cursor: pointer;
    transition: transform 0.1s, box-shadow 0.2s;
  }
  
  .start-btn:hover {
    transform: scale(1.02);
    box-shadow: 0 4px 15px rgba(255, 210, 0, 0.3);
  }
  
  .start-btn:active {
    transform: scale(0.98);
  }
  
  .keyboard-container {
    width: 100%;
    max-width: 900px;
    background: #0a0a1a;
    border-radius: 12px;
    padding: 20px;
    box-shadow: 0 8px 32px rgba(0,0,0,0.5);
  }
  
  .keyboard {
    position: relative;
    display: flex;
    height: 200px;
    border-radius: 0 0 8px 8px;
    overflow: hidden;
    background: #1a1a1a;
  }
  
  .white-key {
    flex: 1;
    background: linear-gradient(180deg, #f8f8f8 0%, #e8e8e8 100%);
    border-right: 1px solid #ccc;
    border-bottom: 3px solid #bbb;
    cursor: pointer;
    position: relative;
    transition: background 0.05s, transform 0.05s;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    align-items: center;
    padding-bottom: 8px;
    font-size: 0.75rem;
    color: #666;
  }
  
  .white-key:last-child {
    border-right: none;
  }
  
  .white-key.pressed {
    background: linear-gradient(180deg, #fff 0%, #ddd 100%);
    border-bottom: 1px solid #bbb;
    transform: translateY(2px);
    color: #000;
  }
  
  .white-key .note-label {
    pointer-events: none;
  }
  
  .black-key {
    position: absolute;
    width: 55px;
    height: 120px;
    background: linear-gradient(180deg, #333 0%, #111 100%);
    border-radius: 0 0 4px 4px;
    border: 1px solid #000;
    border-top: none;
    cursor: pointer;
    z-index: 10;
    transition: background 0.05s, transform 0.05s;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    align-items: center;
    padding-bottom: 6px;
    color: #888;
    font-size: 0.65rem;
  }
  
  .black-key.pressed {
    background: linear-gradient(180deg, #555 0%, #222 100%);
    transform: translateY(2px);
    color: #fff;
  }
  
  .key-hint {
    position: absolute;
    bottom: -22px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 0.65rem;
    color: #ffd200;
    font-family: monospace;
    white-space: nowrap;
  }
  
  .status {
    margin-top: 15px;
    color: #888;
    font-size: 0.85rem;
    text-align: center;
  }
  
  .status .pressed-keys {
    color: #ffd200;
    font-weight: bold;
  }
</style>
</head>
<body>

<h1>Piano Synthesizer</h1>
<p class="subtitle">Click keys or use your computer keyboard • ADSR envelope synthesizer</p>

<div class="controls">
  <div class="control-group">
    <label>Attack</label>
    <input type="range" id="attack" min="0.001" max="2" step="0.001" value="0.005">
    <span class="value" id="attack-val">0.005s</span>
  </div>
  <div class="control-group">
    <label>Decay</label>
    <input type="range" id="decay" min="0.01" max="2" step="0.001" value="0.1">
    <span class="value" id="decay-val">0.100s</span>
  </div>
  <div class="control-group">
    <label>Sustain</label>
    <input type="range" id="sustain" min="0" max="1" step="0.01" value="0.3">
    <span class="value" id="sustain-val">0.30</span>
  </div>
  <div class="control-group">
    <label>Release</label>
    <input type="range" id="release" min="0.01" max="5" step="0.01" value="0.5">
    <span class="value" id="release-val">0.50s</span>
  </div>
  <button class="start-btn" id="start-btn">▶ Start Audio</button>
</div>

<div class="keyboard-container">
  <div class="keyboard" id="keyboard"></div>
  <div class="status" id="status">Press a key or click the piano to play</div>
</div>

<script src="tone.min.js"></script>
<script>
// ... JS code
</script>

</body>
</html>
```

Now the JS. Let me think about the structure:

```js
const NOTES = {
  // Octave 4
  'C4': { freq: 261.63, whiteIndex: 0, black: false },
  'C#4': { freq: 277.18, whiteIndex: 0, black: true }, // between C4 and D4
  'D4': { freq: 293.66, whiteIndex: 1, black: false },
  'D#4': { freq: 311.13, whiteIndex: 1, black: true },
  'E4': { freq: 329.63, whiteIndex: 2, black: false },
  'F4': { freq: 349.23, whiteIndex: 3, black: false },
  'F#4': { freq: 369.99, whiteIndex: 3, black: true },
  'G4': { freq: 392.00, whiteIndex: 4, black: false },
  'G#4': { freq: 415.30, whiteIndex: 4, black: true },
  'A4': { freq: 440.00, whiteIndex: 5, black: false },
  'A#4': { freq: 466.16, whiteIndex: 5, black: true },
  'B4': { freq: 493.88, whiteIndex: 6, black: false },
  // Octave 5
  'C5': { freq: 523.25, whiteIndex: 7, black: false },
  'C#5': { freq: 554.37, whiteIndex: 7, black: true },
  'D5': { freq: 587.33, whiteIndex: 8, black: false },
  'D#5': { freq: 622.25, whiteIndex: 8, black: true },
  'E5': { freq: 659.25, whiteIndex: 9, black: false },
  'F5': { freq: 698.46, whiteIndex: 10, black: false },
  'F#5': { freq: 739.99, whiteIndex: 10, black: true },
  'G5': { freq: 783.99, whiteIndex: 11, black: false },
  'G#5': { freq: 830.61, whiteIndex: 11, black: true },
  'A5': { freq: 880.00, whiteIndex: 12, black: false },
  'A#5': { freq: 932.33, whiteIndex: 12, black: true },
  'B5': { freq: 987.77, whiteIndex: 13, black: false },
};
```

Actually, let me structure the data more cleanly. I'll define white keys and black keys separately.

White keys (per octave, 7 keys): C, D, E, F, G, A, B
Black keys (per octave, 5 keys): C#, D#, F#, G#, A#

For 2 octaves (C4-B5):
- 14 white keys (indices 0-13)
- 10 black keys

Let me define arrays:

```js
const whiteKeys = [];
const blackKeys = [];

const octaves = [4, 5];
const whiteNotes = ['C', 'D', 'E', 'F', 'G', 'A', 'B'];
const blackNotes = ['C#', 'D#', 'F#', 'G#', 'A#'];

let whiteIndex = 0;
octaves.forEach(oct => {
  whiteNotes.forEach(note => {
    const name = note + oct;
    whiteKeys.push({ name, freq: Tone.Frequency(name).toFrequency(), whiteIndex });
    whiteIndex++;
  });
});

// Black keys positioned between specific white keys
// C# between C(whiteIndex) and D(whiteIndex+1)
// D# between D and E
// F# between F and G
// G# between G and A
// A# between A and B
// So black key at boundary after whiteIndex, whiteIndex is the index of the white key to the LEFT
octaves.forEach(oct => {
  const whiteStartIndex = (oct - 4) * 7;
  blackNotes.forEach((note, i) => {
    // Position: after white key at whiteStartIndex + blackNoteLeftWhiteIndex[i]
    const leftWhiteIndices = [0, 1, 3, 4, 5]; // C->between C&D, D->between D&E, F->between F&G, G->between G&A, A->between A&B
    const leftIdx = whiteStartIndex + leftWhiteIndices[i];
    const name = note + oct;
    blackKeys.push({ 
      name, 
      freq: Tone.Frequency(name).toFrequency(), 
      leftWhiteIndex: leftIdx,
      rightWhiteIndex: leftIdx + 1
    });
  });
});
```

Then when rendering:
- White keys: flex: 1 each, total 14
- Black keys: positioned absolutely, left = (leftWhiteIndex + 1) * whiteKeyWidth - blackKeyWidth / 2

For the keyboard layout:
- White key width = keyboardWidth / 14
- Black key width = whiteKeyWidth * 0.55 (or fixed 55px)
- Black key left = (leftWhiteIndex + 1) * whiteKeyWidth - blackKeyWidth / 2

Let me use a fixed black key width of 55px and compute white key width from the container width.

Actually, I should use flex for white keys and absolute positioning for black keys. Let me use JS to compute positions.

```js
function renderKeyboard() {
  const keyboard = document.getElementById('keyboard');
  keyboard.innerHTML = '';
  
  const whiteKeyWidth = keyboard.offsetWidth / whiteKeys.length;
  const blackKeyWidth = Math.min(55, whiteKeyWidth * 0.6);
  
  // Render white keys
  whiteKeys.forEach((key, i) => {
    const el = document.createElement('div');
    el.className = 'white-key';
    el.dataset.note = key.name;
    el.dataset.freq = key.freq;
    el.innerHTML = `<span class="note-label">${key.name}</span><span class="key-hint">${getHint(key.name)}</span>`;
    keyboard.appendChild(el);
  });
  
  // Render black keys
  blackKeys.forEach(key => {
    const el = document.createElement('div');
    el.className = 'black-key';
    el.dataset.note = key.name;
    el.dataset.freq = key.freq;
    const left = (key.leftWhiteIndex + 1) * whiteKeyWidth - blackKeyWidth / 2;
    el.style.left = left + 'px';
    el.style.width = blackKeyWidth + 'px';
    el.style.height = '120px';
    el.innerHTML = `<span class="note-label">${key.name}</span>`;
    keyboard.appendChild(el);
  });
}
```

For the key hints (computer keyboard keys):
```js
const keyMap = {
  // Octave 4
  'a': 'C4', 'w': 'C#4', 's': 'D4', 'e': 'D#4', 'd': 'E4',
  'f': 'F4', 't': 'F#4', 'g': 'G4', 'y': 'G#4', 'h': 'A4',
  'u': 'A#4', 'j': 'B4',
  // Octave 5
  'z': 'C5', '2': 'C#5', 'x': 'D5', '3': 'D#5', 'c': 'E5',
  'v': 'F5', '5': 'F#5', 'b': 'G5', '6': 'G#5', 'n': 'A5',
  '7': 'A#5', 'm': 'B5'
};
```

For the computer keyboard handling:
```js
const pressedKeys = new Set();

document.addEventListener('keydown', (e) => {
  if (e.repeat) return;
  const key = e.key.toLowerCase();
  if (keyMap[key]) {
    e.preventDefault();
    playNote(keyMap[key]);
    pressedKeys.add(key);
  }
});

document.addEventListener('keyup', (e) => {
  const key = e.key.toLowerCase();
  if (keyMap[key]) {
    e.preventDefault();
    stopNote(keyMap[key]);
    pressedKeys.delete(key);
  }
});
```

For mouse handling:
```js
function setupMouseHandlers() {
  const keyboard = document.getElementById('keyboard');
  
  keyboard.addEventListener('mousedown', (e) => {
    const keyEl = e.target.closest('.white-key, .black-key');
    if (keyEl) {
      playNote(keyEl.dataset.note);
      keyEl.classList.add('pressed');
      // Track mouse down for drag
      window._mouseDownNote = keyEl.dataset.note;
      window._mouseDownEl = keyEl;
    }
  });
  
  document.addEventListener('mousemove', (e) => {
    if (window._mouseDownEl) {
      // Check if mouse is over a different key
      const elBelow = document.elementFromPoint(e.clientX, e.clientY);
      const keyEl = elBelow?.closest?.('.white-key, .black-key');
      if (keyEl && keyEl !== window._mouseDownEl) {
        // Release previous
        window._mouseDownEl.classList.remove('pressed');
        stopNote(window._mouseDownEl.dataset.note);
        // Play new
        keyEl.classList.add('pressed');
        playNote(keyEl.dataset.note);
        window._mouseDownEl = keyEl;
      }
    }
  });
  
  document.addEventListener('mouseup', () => {
    if (window._mouseDownEl) {
      window._mouseDownEl.classList.remove('pressed');
      stopNote(window._mouseDownEl.dataset.note);
      window._mouseDownEl = null;
    }
  });
}
```

For the synth:
```js
let synth = null;

function initSynth() {
  synth = new Tone.PolySynth(Tone.Synth, {
    oscillator: { type: 'triangle' },
    envelope: {
      attack: 0.005,
      decay: 0.1,
      sustain: 0.3,
      release: 0.5
    }
  }).toDestination();
}

function updateEnvelope() {
  if (!synth) return;
  const attack = parseFloat(document.getElementById('attack').value);
  const decay = parseFloat(document.getElementById('decay').value);
  const sustain = parseFloat(document.getElementById('sustain').value);
  const release = parseFloat(document.getElementById('release').value);
  
  synth.voices.forEach(voice => {
    voice.envelope.attack = attack;
    voice.envelope.decay = decay;
    voice.envelope.sustain = sustain;
    voice.envelope.release = release;
  });
  
  // Update display
  document.getElementById('attack-val').textContent = attack.toFixed(3) + 's';
  document.getElementById('decay-val').textContent = decay.toFixed(3) + 's';
  document.getElementById('sustain-val').textContent = sustain.toFixed(2);
  document.getElementById('release-val').textContent = release.toFixed(2) + 's';
}

document.getElementById('attack').addEventListener('input', updateEnvelope);
document.getElementById('decay').addEventListener('input', updateEnvelope);
document.getElementById('sustain').addEventListener('input', updateEnvelope);
document.getElementById('release').addEventListener('input', updateEnvelope);
```

For playing/stopping:
```js
function playNote(note) {
  if (Tone.context.state !== 'running') return;
  if (!synth) return;
  synth.triggerAttack(note);
  updateStatus(note + ' pressed');
}

function stopNote(note) {
  if (!synth) return;
  synth.triggerRelease(note);
}
```

For the start button:
```js
document.getElementById('start-btn').addEventListener('click', async () => {
  await Tone.start();
  initSynth();
  updateEnvelope();
  document.getElementById('start-btn').textContent = '✓ Audio Ready';
  document.getElementById('start-btn').style.background = 'linear-gradient(135deg, #4ade80, #22c55e)';
  updateStatus('Audio engine ready — play away!');
});
```

Now, one issue: when the user clicks a key before starting audio, we should show a message. Let me handle that.

Also, I should handle window resize for the keyboard layout.

Let me also add a nice touch: when ADSR sliders change, show a visual indication.

Let me also think about the note labels. White keys should show the full name (C4, D4, etc.) and also maybe the octave. Black keys are smaller so maybe just show C#4 etc.

For the key hints on white keys, I'll show the computer key. For black keys, also show the key.

Wait, with my layout, black keys have the key hint positioned below them. But black keys are positioned absolutely over white keys, so the hint would overlap with the white key below. Let me handle this carefully.

Actually, for black keys, I'll show the hint inside the key (since they're tall enough) or position the hint differently. Let me put hints inside black keys too, at the bottom.

Hmm, let me reconsider the layout. For white keys:
- Bottom area: note label (e.g., "C4")
- Below the key (negative margin): computer key hint (e.g., "A")

For black keys:
- Bottom area inside the key: note label (e.g., "C#4")
- Below the key: computer key hint

But the hint for a black key would overlap with the white key beneath it. That's actually fine visually if I position it correctly. Or I could put the hint inside the black key.

Let me put hints inside both key types, at the bottom of each key.

For white keys: note label at bottom, small hint above it or below the keyboard.
Actually, let me keep it simple: note label inside the key, and a separate hint area below the keyboard showing all key mappings.

Or, I can put the computer key hint on each key, positioned cleverly.

Let me go with: note label on each key (inside), and computer key hint shown below the key using absolute positioning with negative bottom.

For black keys, the hint would appear below the black key, which is above the white key. So it would float in the gap between black keys. That could look messy. 

Alternative: show the hint INSIDE the black key at the bottom, in a small font.

Let me do: 
- White keys: note name at bottom of key (inside), with a small computer key hint just below the keyboard (absolute positioned, negative bottom)
- Black keys: note name at bottom inside the key, computer key hint also inside the key at the very bottom (small, gray)

This is cleaner. Let me implement this.

Actually, let me simplify: put both note name and computer key hint inside each key, at the bottom.

White key:
```
+----------+
|          |
|          |
|          |
|    C4    |
|   [A]    |
+----------+
```

Black key:
```
+----------+
|          |
|          |
|   C#4    |
|   [W]    |
+----------+
```

Where [A] and [W] are the computer keyboard keys.

This is clean and informative. Let me implement it.

Let me refine the styling:

```css
.white-key {
  flex: 1;
  background: linear-gradient(180deg, #f0f0f0 0%, #e0e0e0 100%);
  border-right: 1px solid #ccc;
  border-bottom: 3px solid #bbb;
  cursor: pointer;
  position: relative;
  transition: background 0.05s, transform 0.05s;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  align-items: center;
  padding-bottom: 10px;
  font-size: 0.7rem;
  color: #555;
  z-index: 1;
}

.white-key .note-name {
  font-weight: 600;
  font-size: 0.8rem;
  margin-bottom: 2px;
}

.white-key .key-hint {
  font-size: 0.6rem;
  color: #ffd200;
  font-family: monospace;
  background: rgba(255,210,0,0.1);
  padding: 1px 6px;
  border-radius: 3px;
}

.white-key.pressed {
  background: linear-gradient(180deg, #fff 0%, #ddd 100%);
  border-bottom: 1px solid #bbb;
  transform: translateY(2px);
}

.black-key {
  position: absolute;
  width: 55px;
  height: 120px;
  background: linear-gradient(180deg, #444 0%, #222 100%);
  border-radius: 0 0 4px 4px;
  border: 1px solid #000;
  border-top: none;
  cursor: pointer;
  z-index: 10;
  transition: background 0.05s, transform 0.05s;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  align-items: center;
  padding-bottom: 8px;
  color: #aaa;
  font-size: 0.6rem;
}

.black-key .note-name {
  font-weight: 600;
  font-size: 0.7rem;
  margin-bottom: 2px;
  color: #ccc;
}

.black-key .key-hint {
  font-size: 0.55rem;
  color: #ffd200;
  font-family: monospace;
  background: rgba(255,210,0,0.15);
  padding: 1px 5px;
  border-radius: 2px;
}

.black-key.pressed {
  background: linear-gradient(180deg, #666 0%, #333 100%);
  transform: translateY(2px);
}
```

Now let me also think about the overall design. I want it to look polished.

Let me also add octave labels or separators between octaves.

Actually, let me add a visual separator between octave 4 and octave 5 on the keyboard. I can add a small marker.

Or I can just label the keys clearly with octave numbers and it'll be obvious.

Let me finalize and write the code.

One more thing: I need to handle the case where Tone.js hasn't been started yet. The start button will handle that. Before starting, clicking keys should show a message "Click 'Start Audio' first".

Also, I should make the keyboard responsive. On smaller screens, the keys should scale down.

Let me use a fixed height for the keyboard area and let the width be responsive.

Alright, let me write the complete code now.

Actually, I realize I should also handle the case where the user presses multiple keys simultaneously (polyphony). Tone.PolySynth handles this.

But there's a subtlety: when the user clicks and holds a key, then clicks another key, the first should keep playing. With my mouse handling, I track the currently pressed key and switch. But what if the user wants to play multiple keys at once with the mouse?

For mouse: mousedown on a key plays it, mouseup releases it. If the user drags to another key, the previous is released and the new one plays. This is fine for monophonic playing. For polyphonic, the user can click multiple keys without dragging.

Actually, a better approach for mouse: track all keys that are currently pressed via mouse, and only release when mouseup happens on that specific key. But this is complex. Let me keep it simple: mouse down plays, mouse up releases. Dragging switches keys.

For computer keyboard: keydown plays, keyup releases. Multiple keys can be held simultaneously. This is polyphonic.

This is a good design. Let me implement it.

Now let me also add a visual indicator for which computer keys are currently pressed.

```js
function updateStatus(message) {
  document.getElementById('status').textContent = message;
}
```

Let me also show the currently pressed computer keys:
```js
function updatePressedKeysDisplay() {
  if (pressedKeys.size > 0) {
    const keys = Array.from(pressedKeys).map(k => k.toUpperCase()).join(' ');
    document.getElementById('status').innerHTML = `Pressed: <span class="pressed-keys">${keys}</span>`;
  } else {
    document.getElementById('status').textContent = 'Press a key or click the piano to play';
  }
}
```

Call this on keydown and keyup.

Alright, I think I have a complete plan. Let me write the code.

One more consideration: the ADSR sliders. I want them to look nice and update in real-time. The value displays should show the current value.

Let me also add some preset buttons (e.g., "Piano", "Pad", "Bump") that set the ADSR to different values. Actually, that might be over-engineering. Let me keep it simple with just the 4 sliders.

But I could add a few presets for fun. Let me add 3 presets: "Piano" (short attack, medium decay, low sustain, medium release), "Pad" (slow attack, long decay, high sustain, long release), "Bump" (very short attack, short decay, no sustain, short release).

Actually, let me keep it focused on the core requirements: piano keyboard, mouse + computer keys, ADSR envelope, visual feedback. Presets are a nice-to-have but not required.

Let me add them as a nice touch though. 3 small preset buttons.

OK let me write the final code.

Actually, I realize I should double-check: does `Tone.Frequency(name).toFrequency()` work for note names like "C4"? Yes, Tone.Frequency can parse note names.

Let me also verify: `Tone.PolySynth` with `Tone.Synth` voices - can I set the envelope on individual voices? Yes, each voice is a Synth instance with its own envelope.

But wait, in Tone.js v14+, when you create a PolySynth with a voice type, the voices are created lazily. So `synth.voices` might be empty until a note is played. Let me handle this by setting the envelope on the PolySynth's options and also updating voices when they're created.

Actually, the standard way in Tone.js is:
```js
const synth = new Tone.PolySynth(Tone.Synth, {
  envelope: { attack: 0.005, decay: 0.1, sustain: 0.3, release: 0.5 }
});
```

And to update:
```js
synth.set({ envelope: { attack: 0.1, ... } });
```

But `set` on PolySynth might not update existing voices. Let me check...

In Tone.js, `PolySynth.set()` sets properties on the PolySynth itself, not on the voices. To update voice envelopes, you need to iterate over `synth.voices` and set each one.

But `synth.voices` is a Tone.Set (or array-like) that contains the active voices. When you call `triggerAttack`, voices are created as needed. So if no notes are playing, `synth.voices` might be empty.

To handle this properly:
1. Set the envelope on the PolySynth's default options (affects new voices)
2. Iterate over existing voices to update them

```js
function updateEnvelope() {
  const attack = parseFloat(document.getElementById('attack').value);
  const decay = parseFloat(document.getElementById('decay').value);
  const sustain = parseFloat(document.getElementById('sustain').value);
  const release = parseFloat(document.getElementById('release').value);
  
  // Update existing voices
  synth.voices.forEach(voice => {
    voice.envelope.attack = attack;
    voice.envelope.decay = decay;
    voice.envelope.sustain = sustain;
    voice.envelope.release = release;
  });
  
  // Update the default envelope for new voices
  synth.set({
    envelope: { attack, decay, sustain, release }
  });
}
```

Hmm, actually `synth.set({envelope: {...}})` might not work as expected for PolySynth. Let me use a different approach.

In Tone.js, the recommended way to configure a PolySynth's voice is to pass the options when creating it. To change them later, you can access the voice prototype or create new voices.

Actually, the simplest approach that works: just create the PolySynth with the initial envelope, and when the user changes the sliders, dispose the old synth and create a new one with the new envelope. But this would cut off any currently playing notes.

Alternative: use individual Synth instances for each note. But that's more complex.

Let me just use the `synth.voices.forEach` approach and also set on the synth's options. In practice, this works fine in Tone.js.

Actually, I just realized: in Tone.js, `PolySynth` has a `voice` property that is the constructor function. And `synth.voices` returns the active voices. When you call `synth.set()`, it sets on the PolySynth, not the voices.

The cleanest approach:
```js
// Store initial options
let currentEnvelope = { attack: 0.005, decay: 0.1, sustain: 0.3, release: 0.5 };

function initSynth() {
  synth = new Tone.PolySynth(Tone.Synth, {
    oscillator: { type: 'triangle' },
    envelope: currentEnvelope
  }).toDestination();
}

function updateEnvelope() {
  currentEnvelope = {
    attack: parseFloat(document.getElementById('attack').value),
    decay: parseFloat(document.getElementById('decay').value),
    sustain: parseFloat(document.getElementById('sustain').value),
    release: parseFloat(document.getElementById('release').value),
  };
  
  // Update existing voices
  synth.voices.forEach(voice => {
    Object.assign(voice.envelope, currentEnvelope);
  });
  
  // Update the options for new voices
  synth.options.envelope = currentEnvelope;
}
```

Hmm, `synth.options` might not be directly accessible. Let me just use the forEach approach and trust that new voices will use the latest settings from the PolySynth's internal state.

Actually, in Tone.js, when you call `triggerAttack` on a PolySynth, it creates a new voice using the options passed to the PolySynth constructor. If you want to change the options for new voices, you need to recreate the PolySynth or use a different approach.

But wait, in Tone.js v14+, PolySynth has a `set` method that can update the voice options:
```js
synth.set({ envelope: { attack: 0.1 } });
```

This should update both the internal options and the existing voices. Let me just use this.

Actually, I've seen that in Tone.js, `PolySynth.set()` does work to update the envelope for both existing and new voices. Let me just use it.

Let me test this mentally with Tone.js source... In Tone.js PolySynth:
```js
set(options) {
  super.set(options);
  // Also set on voices
  this.voices.forEach(voice => voice.set(options));
}
```

Wait, I'm not sure if this is exactly how it works. Let me just use a safe approach:

```js
function updateEnvelope() {
  const attack = parseFloat(document.getElementById('attack').value);
  const decay = parseFloat(document.getElementById('decay').value);
  const sustain = parseFloat(document.getElementById('sustain').value);
  const release = parseFloat(document.getElementById('release').value);
  
  const env = { attack, decay, sustain, release };
  
  // Update existing voices
  synth.voices.forEach(voice => {
    voice.envelope.attack = attack;
    voice.envelope.decay = decay;
    voice.envelope.sustain = sustain;
    voice.envelope.release = release;
  });
  
  // Also try set on the synth (for new voices)
  try {
    synth.set({ envelope: env });
  } catch(e) {}
}
```

This should be safe and work in most cases.

OK, I think I've thought about this enough. Let me write the final code.

One more thing: I should also handle the case where the user resizes the window. The keyboard should re-render. Let me add a resize handler.

```js
let resizeTimeout;
window.addEventListener('resize', () => {
  clearTimeout(resizeTimeout);
  resizeTimeout = setTimeout(() => renderKeyboard(), 100);
});
```

Alright, let me write the complete HTML now. I'll be thorough and make it polished.

Wait, I also want to add a nice feature: when a note is playing, show the note name somewhere prominently. And maybe show a visualizer or something. But let me keep it focused.

Let me also add a small "octave" indicator or label between the two octaves on the keyboard.

OK, writing the code now. Let me make it clean and well-organized.

For the keyboard rendering, I need to be careful about the positioning. Let me use a container with `position: relative` and compute pixel positions for black keys.

Here's my final approach for rendering:

```js
function renderKeyboard() {
  const keyboard = document.getElementById('keyboard');
  keyboard.innerHTML = '';
  
  const width = keyboard.offsetWidth;
  const whiteKeyCount = whiteKeys.length; // 14
  const whiteKeyWidth = width / whiteKeyCount;
  const blackKeyWidth = Math.min(60, whiteKeyWidth * 0.6);
  
  // White keys
  whiteKeys.forEach((key) => {
    const el = document.createElement('div');
    el.className = 'white-key';
    el.dataset.note = key.name;
    el.innerHTML = `
      <span class="note-name">${key.name}</span>
      <span class="key-hint">${getHint(key.name)}</span>
    `;
    keyboard.appendChild(el);
  });
  
  // Black keys
  blackKeys.forEach((key) => {
    const el = document.createElement('div');
    el.className = 'black-key';
    el.dataset.note = key.name;
    const left = (key.leftWhiteIndex + 1) * whiteKeyWidth - blackKeyWidth / 2;
    el.style.left = left + 'px';
    el.style Width = blackKeyWidth + 'px';
    el.innerHTML = `
      <span class="note-name">${key.name}</span>
      <span class="key-hint">${getHint(key.name)}</span>
    `;
    keyboard.appendChild(el);
  });
}
```

Wait, I need to compute `leftWhiteIndex` correctly. Let me trace through:

For octave 4 (white keys C4, D4, E4, F4, G4, A4, B4 at indices 0-6):
- C#4 is between C4 (index 0) and D4 (index 1). The boundary is at x = 1 * whiteKeyWidth. So left = 1 * whiteKeyWidth - blackKeyWidth/2. The leftWhiteIndex is 0 (the white key to the left of the boundary).
- D#4 is between D4 (index 1) and E4 (index 2). left = 2 * whiteKeyWidth - blackKeyWidth/2. leftWhiteIndex = 1.
- F#4 is between F4 (index 3) and G4 (index 4). left = 4 * whiteKeyWidth - blackKeyWidth/2. leftWhiteIndex = 3.
- G#4 is between G4 (index 4) and A4 (index 5). left = 5 * whiteKeyWidth - blackKeyWidth/2. leftWhiteIndex = 4.
- A#4 is between A4 (index 5) and B4 (index 6). left = 6 * whiteKeyWidth - blackKeyWidth/2. leftWhiteIndex = 5.

For octave 5 (white keys C5, D5, E5, F5, G5, A5, B5 at indices 7-13):
- C#5: between C5 (7) and D5 (8). leftWhiteIndex = 7.
- D#5: between D5 (8) and E5 (9). leftWhiteIndex = 8.
- F#5: between F5 (10) and G5 (11). leftWhiteIndex = 10.
- G#5: between G5 (11) and A5 (12). leftWhiteIndex = 11.
- A#5: between A5 (12) and B5 (13). leftWhiteIndex = 12.

So the leftWhiteIndices for black notes (C#, D#, F#, G#, A#) are:
- C#: 0 (first white key of the octave)
- D#: 1 (second white key)
- F#: 3 (fourth white key)
- G#: 4 (fifth white key)
- A#: 5 (sixth white key)

For octave 5, add 7 to each:
- C#5: 7
- D#5: 8
- F#5: 10
- G#5: 11
- A#5: 12

Let me define this in code:

```js
const blackNoteOffsets = [0, 1, 3, 4, 5]; // offsets within an octave for C#, D#, F#, G#, A#
```

Then:
```js
octaves.forEach(oct => {
  const whiteStartIndex = (oct - 4) * 7;
  blackNotes.forEach((note, i) => {
    const leftWhiteIndex = whiteStartIndex + blackNoteOffsets[i];
    const name = note + oct;
    blackKeys.push({
      name,
      freq: Tone.Frequency(name).toFrequency(),
      leftWhiteIndex
    });
  });
});
```

This is correct.

Now for the hints (computer keyboard keys):

```js
const hintMap = {
  'C4': 'A', 'C#4': 'W', 'D4': 'S', 'D#4': 'E', 'E4': 'D',
  'F4': 'F', 'F#4': 'T', 'G4': 'G', 'G#4': 'Y', 'A4': 'H',
  'A#4': 'U', 'B4': 'J',
  'C5': 'Z', 'C#5': '2', 'D5': 'X', 'D#5': '3', 'E5': 'C',
  'F5': 'V', 'F#5': '5', 'G5': 'B', 'G#5': '6', 'A5': 'N',
  'A#5': '7', 'B5': 'M'
};

function getHint(note) {
  return hintMap[note] || '';
}
```

For the keydown/keyup handlers:
```js
const pressedKeys = new Set();

document.addEventListener('keydown', (e) => {
  if (e.repeat) return;
  const key = e.key.toLowerCase();
  const note = hintMapReverse[key]; // need reverse map
  if (note) {
    e.preventDefault();
    if (!audioStarted) {
      updateStatus('Click "Start Audio" first!');
      return;
    }
    playNote(note);
    pressedKeys.add(key);
    updatePressedKeysDisplay();
    // Visual feedback on keyboard
    highlightKeyByNote(note, true);
  }
});

document.addEventListener('keyup', (e) => {
  const key = e.key.toLowerCase();
  const note = hintMapReverse[key];
  if (note) {
    e.preventDefault();
    stopNote(note);
    pressedKeys.delete(key);
    updatePressedKeysDisplay();
    highlightKeyByNote(note, false);
  }
});
```

I need a reverse map from computer key to note name. Let me build it:

```js
const computerKeyToNote = {};
Object.entries(hintMap).forEach(([note, key]) => {
  computerKeyToNote[key] = note;
});
```

For highlighting keys:
```js
function highlightKeyByNote(note, pressed) {
  const el = document.querySelector(`[data-note="${note}"]`);
  if (el) {
    el.classList.toggle('pressed', pressed);
  }
}
```

OK, I think I have everything. Let me write the complete HTML.

Actually, I want to double-check one thing: the `e.preventDefault()` on keydown/keyup. This prevents the key from being typed in the page. I should do this for keys that are mapped to notes. For other keys (like Shift, Ctrl, etc.), I should not prevent default.

Also, I should be careful with `e.repeat`. When a key is held down, the browser fires repeated keydown events. I should ignore repeats to avoid retriggering notes.

Alright, let me write the complete code now. I'll aim for a polished, professional look.

Let me also add a subtle animation/glow to pressed keys for extra visual feedback.

For the ADSR section, let me add a small label showing the current "preset" name based on the values. Or just keep it simple with the raw values.

Let me finalize the design and write the code.

Actually, let me also add a volume/gain control. No, the requirements say ADSR envelope, so let me focus on that. A master volume could be a nice addition but not required.

OK, writing now. Let me make it comprehensive and polished.

Actually, one more thing: I want to make sure the black keys are properly clickable. Since they're positioned absolutely over white keys, clicks on black keys should not trigger white key events. I'll use `z-index` to ensure black keys are on top, and the click handler will use `e.target.closest()` to find the actual key element.

For mouse drag across keys: when the user mousedowns on a key, I play it. When they mouseover another key while holding the mouse, I switch. When they mouseup, I release.

Let me implement this with a clean approach:

```js
let mouseDownNote = null;
let mouseDownElement = null;

keyboard.addEventListener('mousedown', (e) => {
  const keyEl = e.target.closest('.white-key, .black-key');
  if (!keyEl) return;
  e.preventDefault();
  if (!audioStarted) {
    updateStatus('Click "Start Audio" first!');
    return;
  }
  const note = keyEl.dataset.note;
  playNote(note);
  keyEl.classList.add('pressed');
  mouseDownNote = note;
  mouseDownElement = keyEl;
});

document.addEventListener('mousemove', (e) => {
  if (!mouseDownElement) return;
  const elBelow = document.elementFromPoint(e.clientX, e.clientY);
  const keyEl = elBelow?.closest?.('.white-key, .black-key');
  if (keyEl && keyEl !== mouseDownElement) {
    // Release old
    mouseDownElement.classList.remove('pressed');
    stopNote(mouseDownNote);
    // Play new
    const newNote = keyEl.dataset.note;
    playNote(newNote);
    keyEl.classList.add('pressed');
    mouseDownNote = newNote;
    mouseDownElement = keyEl;
  }
});

document.addEventListener('mouseup', () => {
  if (mouseDownElement) {
    mouseDownElement.classList.remove('pressed');
    stopNote(mouseDownNote);
    mouseDownNote = null;
    mouseDownElement = null;
  }
});
```

This handles mouse dragging across keys nicely.

Now let me write the complete HTML file. I'll be thorough.

For the design, let me go with a dark theme with gold accents (matching the start button gradient).

Here's my complete plan:
1. Dark background (#1a1a2e)
2. Gold/amber accents (#ffd200)
3. Piano keyboard with realistic key styling
4. ADSR sliders with clean styling
5. Start Audio button
6. Status display
7. Responsive layout

Let me write it all now.

Hmm, for the keyboard width, I want it to be responsive. On a 900px container, with 14 white keys, each key is ~64px. That's reasonable. On mobile (320px), each key is ~23px which is small but usable.

For the black key width, I'll use 55px as a fixed size, which works well when white keys are 60px+. On smaller screens, I'll scale it down.

Actually, let me use a slightly different approach: set a min-width for the keyboard and allow horizontal scrolling on very small screens. Or just make it responsive with smaller keys.

Let me use `min-width: 600px` for the keyboard container and center it. On smaller screens, it can scroll horizontally. This ensures the keys are always a reasonable size.

Actually, for a better mobile experience, let me make it responsive but with a minimum key size. I'll use `flex: 1` for white keys and compute black key width as a percentage.

Let me use this approach:
- White keys: `flex: 1` (equal width)
- Black keys: width = `min(60px, whiteKeyWidth * 0.6)` computed in JS

On window resize, re-render the keyboard.

OK, final code time. Let me write it.

Let me also add a small visual indicator showing which octave each key belongs to. I can add a subtle background color difference or a label.

Actually, the note names already include the octave (C4, C5, etc.), so it's clear. Let me not over-complicate it.

One more thing: I should add `touch` support for mobile. Let me add touchstart/touchmove/touchend handlers similar to mouse.

```js
keyboard.addEventListener('touchstart', (e) => {
  const touch = e.touches[0];
  const elBelow = document.elementFromPoint(touch.clientX, touch.clientY);
  const keyEl = elBelow?.closest?.('.white-key, .black-key');
  if (!keyEl) return;
  e.preventDefault();
  if (!audioStarted) {
    updateStatus('Click "Start Audio" first!');
    return;
  }
  const note = keyEl.dataset.note;
  playNote(note);
  keyEl.classList.add('pressed');
  mouseDownNote = note;
  mouseDownElement = keyEl;
}, { passive: false });

document.addEventListener('touchmove', (e) => {
  if (!mouseDownElement) return;
  const touch = e.touches[0];
  const elBelow = document.elementFromPoint(touch.clientX, touch.clientY);
  const keyEl = elBelow?.closest?.('.white-key, .black-key');
  if (keyEl && keyEl !== mouseDownElement) {
    mouseDownElement.classList.remove('pressed');
    stopNote(mouseDownNote);
    const newNote = keyEl.dataset.note;
    playNote(newNote);
    keyEl.classList.add('pressed');
    mouseDownNote = newNote;
    mouseDownElement = keyEl;
  }
}, { passive: false });

document.addEventListener('touchend', () => {
  if (mouseDownElement) {
    mouseDownElement.classList.remove('pressed');
    stopNote(mouseDownNote);
    mouseDownNote = null;
    mouseDownElement = null;
  }
});
```

Good. Let me include touch support.

Alright, NOW let me write the complete code. I'll put it all together.

Let me also think about what happens when Tone.js is loaded but not started. `Tone.context.state` will be 'suspended'. The `Tone.start()` call resumes it. After that, notes can play.

I should also handle the case where the user clicks a key before starting audio. Show a helpful message.

Let me finalize everything and write the

The user wants me to build a playable piano keyboard web app using Tone.js (loaded from the provided tone.min.js). Let me think about what's needed:

1. A visual piano keyboard with white and black keys
2. Mouse click to play notes
3. Computer keyboard keys to play notes (mapping computer keys to piano keys)
4. ADSR envelope synthesis using Tone.js
5. Visual key feedback (keys light up when pressed)

I need to figure out the Tone.js API from the minified file. Let me look for key API patterns.

Tone.js typically has:
- `Tone.Synth` or `Tone.PolySynth` 
- `Tone.Oscillator` with `frequency` and `type`


- `Tone.Gain` for volume control
- `Tone.Envelope` or `Tone.AmplitudeEnvelope` for ADSR
- `Tone.Frequency` for note frequencies

For a piano, I'll use a combination of oscillators with proper ADSR envelopes. Looking at the minified code, I can see it has envelope functionality with attack, decay, sustain, release parameters, plus oscillator types and frequency handling. Now I'll design the keyboard layout with white and black keys and map computer keyboard keys to the piano notes.

For the keyboard mapping, I'm thinking through the standard computer-to-piano arrangement where the home row and surrounding keys correspond to specific piano notes.

Now I'm working out the note frequencies using the standard MIDI formula, though I need to double-check my chromatic scale calculations to make sure they're accurate.

Building the piano interface with a visual keyboard layout... Setting up the Tone.js audio components...

I'm creating a monophonic synth with an oscillator, gain stages for envelope shaping, and an ADSR envelope to control the amplitude dynamics. The oscillator's frequency gets controlled directly, and I'm connecting everything through a gain node so the envelope can shape the sound dynamically.

But wait, I should reconsider the architecture here—a piano really needs polyphony to play multiple notes simultaneously, not just a single voice. Let me think about using Tone.PolySynth or building a polyphonic synth instead, since a real piano keyboard requires the ability to press multiple keys at once. I've settled on using Tone.PolySynth to handle multiple notes simultaneously, which gives me the polyphonic capability I need. Now I'm building out the complete HTML structure with the UI.

Building the keyboard layout... Still writing keyboard styles... Writing the piano layout... Building the piano keyboard layout... Writing keyboard event handlers... Still writing keyboard logic... Still writing the note management logic...

Now I'm building out the UI layout with a header that includes controls for ADSR envelope parameters and a play button.

Building the keyboard visualization... Building the keyboard UI... Let me verify the keyboard mapping I'm using—I need to make sure the computer keys line up correctly with the piano notes from C4 through E5, with the center keys matching up as expected. I've verified all 18 note mappings are correct, so now I'm ready to generate the final file.

The Tone.js library is available. Now I need to build a piano keyboard app with:

1. ADSR envelope synthesis
2. Mouse click interaction on keys
3. Computer keyboard interaction
4. Visual feedback (keys light up when pressed)

Let me design the piano keyboard. I'll use a standard 88-key layout but maybe start with a practical range (like 2-3 octaves) to keep it manageable. I'll use:
- White keys and black keys properly arranged
- ADSR envelope via Tone.js Synth or custom setup


- Mouse: click to press, release to stop
- Computer keyboard: keys like A S D F G H J K L for white keys, W E T Y U O P for black keys (common mapping)

I'm going to use Tone.Synth with a custom envelope for the ADSR synthesis, and I'm thinking through the layout - starting at C4 and going up through several octaves with the standard white and black key arrangement, mapping to keyboard keys across two octaves.

Actually, let me reconsider and go with a full 88-key piano layout instead, starting from A0 to C8, which is more realistic. I'll use Tone.PolySynth to handle multiple notes simultaneously, and I need to figure out which computer keys map to which piano keys - probably using a row-based approach where one row handles the lower octaves and another handles higher ones.

For the keyboard mapping, I'm thinking of using a standard piano layout where the bottom row (Z-M) covers one octave and the top row (Q-P minus the black key positions) covers the next octave up, with the shift keys or number row handling the black keys in between.

Now I'm mapping out the full keyboard layout: the home row handles white keys across two octaves starting from C, the row above handles the sharp/flat notes, and the number row covers the highest octave, with the spacebar reserved for the sustain pedal. I'm setting up a two-octave keyboard layout starting at C4, mapping computer keys across three rows to cover both the white and black keys, with the home row handling the naturals and the upper rows handling the accidentals in the standard piano pattern. I'm settling on a two-octave layout from C4 to B5 with computer key mappings that follow a logical progression—using ZXCVB for the lower octave's white keys, then QWERTYUIOP for the upper octave, with ASDFGHJK for the black keys in between. This keeps the layout ergonomic and avoids awkward mappings like Q=E. I'm mapping out a two-octave keyboard with the home row handling white keys (Z through M for C4-B4) and the number row for the next octave (2 through = for C5-B5), with black keys on the row above (W, E, T, Y, U, O, P) and shift keys for the remaining accidentals.

Actually, let me simplify this and use a cleaner approach with a visual piano keyboard app that includes mouse and keyboard interaction, an ADSR envelope for sound synthesis, and visual feedback when keys are pressed, along with controls for adjusting envelope parameters.

I'm settling on a two-octave layout from C4 to B5 since that's practical for a web interface, using the QWERTY keyboard mapping where the home row handles one octave and the row above handles the next, with dedicated keys for the sharps and flats.

Now I'm ready to build the full implementation.

Mapping out the piano keyboard layout... Building the keyboard UI... Writing the keyboard player logic... I'm reconsidering the key mappings for the upper octave to make them more intuitive—using the top row numbers and symbols instead of the current layout, which should be easier for users to remember and reach.

Now I need to be careful about how computer keys and mouse clicks interact, since they both trigger the same note-on/note-off events but through different mechanisms.

Writing the HTML file...

Let me verify the file looks right and that everything is in order.

Let me verify the HTML is well-formed by checking for any obvious issues, and also test that the Tone.js integration is syntactically correct.

The file is built and validated. Let me provide a summary of what was created.

Let me do a final review of the black key positioning logic — I want to make sure it's correct. Let me look at the actual logic.

The white keys are laid out as flex items. The black keys need to overlay them at correct positions. The standard piano pattern per octave is:

W W B W W B W W B W W B W (7 white, 5 black)

White indices in octave: 0=C, 1=D, 2=E, 3=F, 4=G, 5=A, 6=B


Black keys positioned after specific white keys: C# after C (idx 0), D# after D (idx 1), F# after F (idx 3), G# after G (idx 4), A# after A (idx 5). The offsets should align with these positions so each black key sits correctly between its neighboring white keys.

For positioning, I need to calculate the left edge based on the width of the white key plus gap, then place the black key slightly overlapping. The pattern repeats across both octaves, so I'm iterating through each octave and placing black keys at their corresponding white key indices.

I need to fix the black key positioning and also the note-finding logic. Let me think through the correct approach.

White keys per octave (indices 0-6): C, D, E, F, G, A, B
Black keys (sharps) in an octave: C#, D#, F#, G#, A#

Position of black keys relative to white keys:
- C# sits between C(0) and D(1) → after whiteNotes[0]
- D# sits between D(1) and E(2) → after whiteNotes[1]


- F# sits between F(3) and G(4) → after whiteNotes[3]
- G# sits between G(4) and A(5) → after whiteNotes[4]
- A# sits between A(5) and B(6) → after whiteNotes[5]

So the blackOffsets array should be [0, 1, 3, 4, 5] to position each black key after its preceding white key. The layout pattern of white and black keys across an octave confirms this arrangement. I'm redefining the blackOffsets to represent the index of the white key that each black key sits after, so C# follows C at index 0, D# follows D at index 1, and so on. Then I'm recalculating the left position for each black key based on the white key width and spacing, with the black key centered or offset slightly from the boundary between adjacent white keys.

Rather than manually calculating positions, I think it's cleaner to use flex layout and let the browser handle it—I can position the black keys absolutely with a left offset that's half a white key width minus half a black key width, adjusted by the gap. But I need to reconsider this calculation because the spacing might not work out correctly. I'm refining the positioning formula to center each black key between adjacent white keys by adjusting the left offset calculation—removing the bottom gap from the white key width and accounting for the black key's own width and a small vertical overlap adjustment.

Actually, let me step back and simplify this with a flex container approach where white keys use flex-grow and black keys are positioned absolutely relative to the piano element, calculating their position as the midpoint between consecutive white keys rather than trying to manage all the margin and gap math. I need to calculate the black key position based on the gap between white keys—I'm using the formula `left = (whiteIdx + 0.5) * whiteKeyStep - blackKeyWidth / 2` where `whiteKeyStep` includes both the key width and gap. Let me just simplify this and use a percentage-based approach instead, or stick with pixel values and straightforward math. I've verified the math checks out, so now I'll refactor the code to use clearer variable names for positioning. Actually, I realize I can simplify this by using overflow: visible on the piano container instead—that way I can position black keys as negative margins extending leftward from the white key positions, which eliminates the need for JavaScript positioning altogether. Positioning black keys with negative margins is tricky because I can't target them individually, so I'll stick with JavaScript to position them precisely using offset calculations instead of trying to manage absolute positioning with percentage values.

Let me write out the clean positioning code now.

The code in the file is actually correct — it uses `whiteNotes[base + wIdx]` where `wIdx` is the index of the white note before the black key. Let me trace through it carefully.

The white notes in octave 4 are:
- whiteNotes[0] = C4 (midi 60)
- whiteNotes[1] = D4 (midi 62)


- whiteNotes[2] = E4 (midi 64)
- whiteNotes[3] = F4 (midi 65)
- whiteNotes[4] = G4 (midi 67)
- whiteNotes[5] = A4 (midi 69)
- whiteNotes[6] = B4 (midi 71)

Now checking the black keys: C#4 at midi 61 should sit between C4 and D4, so the code uses `whiteNotes[0 + 1]` and calculates the MIDI as midi + 1, which correctly gives 61.

But wait — I need to verify the `blackOffsets` array is actually correct. The offset for C# should be 0 (positioning after whiteNotes[0]), but the code has it as 1, which would position it after D4 instead. That's the bug I'm seeing.

Looking at the code that finds the note, it uses `whiteNote.midi + 1`, so with offset 1 it gets D4's midi (62) + 1 = 63, which is D#4 — wrong note entirely. I need to fix the offsets array to `[0,1,3,4,5]` and confirm the positioning logic handles this correctly.

Now I'm checking how the left positioning works: the formula `(base + 1) * (wkWidth + wkGap) - bkW - wkGap * 0.3` places the black key after `whiteNotes[base]`. With the correct offsets, a C# key at base 0 positions it right after C4, and a D# key at base 1 places it after D4, which is exactly what I want.

Wait, I need to carefully redo the black key positioning. The issue is:

- blackOffsets = [1,2,4,5,6] — these refer to indices in whiteNotes AFTER which the black key sits
- But actually, black key sits BETWEEN white keys, not after.
- Pattern: W(W) W(B) W W(B) W W(B) W W(B) W W(B) W

Actually wait — the positions of black keys relative to white keys in a piano are:


- C# sits between C and D
- D# sits between D and E
- F# sits between F and G
- G# sits between G and A
- A# sits between A and B

So if whiteNotes = [C, D, E, F, G, A, B] (indices 0-6), then:
- C# sits between C(0) and D(1) → its left edge aligns with the right edge of C
- D# sits between D(1) and E(2) → aligns with right edge of D
- F# sits between F(3) and G(4) → aligns with right edge of F
- G# sits between G(4) and A(5) → aligns with right edge of G
- A# sits between A(5) and B(6) → aligns with right edge of A

So the correct offsets (index of white key BEFORE the black key) are: [0, 1, 3, 4, 5], not [1, 2, 4, 5, 6]. I've been using the wrong indices — I need to shift them back by one to get the right positions. The code uses `blackOffsets` as indices into whiteNotes, treating them as the index AFTER which the black key sits. But that means C# should come after whiteNotes[0], D# after whiteNotes[1], and so on—which gives [0, 1, 3, 4, 5] as the correct offsets. However, the actual code uses [1,2,4,5,6], resulting in incorrect positioning where C# ends up between D and E instead of between C and D. The formula also needs adjustment—instead of calculating left as `(base + 1) * (width + gap) - bW`, I need to use the right edge of the preceding white key.

The core problem is that the code sets each black key's left edge to the left edge of the NEXT white key minus the black key's width, but black keys should actually align with the right edge of the PREVIOUS white key. Since this positions them slightly to the right, I need to account for the gap between white keys in the calculation.

Even with numbers, the offset is consistently wrong—it's off by about one full white key width plus the gap. I need to fix `positionBlackKeys()` to use the correct preceding white key index and adjust the formula to properly align with that key's right edge. Let me also verify the note-finding logic works correctly with these fixed offsets. Now I'm mapping out the exact positions for the black keys in octave 5 — C#5 through A#5 — and I can see the positionBlackKeys function needs to use the correct offsets to align them properly with their neighboring white keys. I see the issue now—the position formula needs to reference the white key's right edge with the proper index, and I should remove the unused blackNames array. Let me refactor this more carefully by calculating the actual left position based on the previous white key's right edge, then write a corrected version of that section. Now I'm working through the positioning logic for black keys—I need the left edge of black key i to align with the right edge of the preceding white key, which means calculating `left` as `(whiteIndex + 1) * (wkWidth + wkGap) - (bkW + overlap)`. The current code is off by one and missing the gap adjustment, so I'm going to fix the positionBlackKeys function and simplify the black key creation logic.

Now let me also remove the unused `BK` variable references and verify the file still passes validation. Let me also check the kbToNote mapping is correct — black key kb indices should map to the right NOTES index. Currently BLACK_KB.forEach maps to WHITE_KB.length + i, but the note lookup in noteOn/noteOff uses `NOTES[WHITE_KB.length + (kbIdx - WHITE_KB.length)].name`. Let me verify this is consistent.

WHITE_KB.length = 14 (2 rows × 7 keys).
BLACK_KB.length = 10 (2 octaves × 5 keys).

kbToNote: WHITE_KB[0..13] → 0..13, BLACK_KB[0..9] → 14..23.

In noteOn/keydown handler:
```
if (kbIdx < WHITE_KB.length) {
    noteName = whiteNotes[kbIdx].name;
} else {
    noteName = NOTES[WHITE_KB.length + (kbIdx - WHITE_KB.length)].name;
}
```

So for a black key with kbIdx = 14 (first black key), we look up NOTES[14 + (14-14)] = NOTES[14]. 

Let me verify NOTES[14]:
NOTES is built as [{midi:60,i:0}, {midi:61,i:1}, {midi:62,i:2}, ...].
NOTES[14] = midi 60 + 14 = 74, i = 2, name = "C#5"? Wait let me recalculate.

NOTES: 2 octaves, 24 notes total (octave 4: indices 0-11, octave 5: indices 12-23).

The black keys in note data are at indices: 1 (C#4), 3 (D#4), 6 (F#4), 8 (G#4), 10 (A#4), 13 (C#5), 15 (D#5), 18 (F#5), 20 (G#5), 22 (A#5).

But NOTES is indexed 0-23 in order. So:
- NOTES[1] = C#4 (midi 61, i=1)
- NOTES[3] = D#4 (midi 63, i=3)
- NOTES[6] = F#4 (midi 66, i=6)
- NOTES[8] = G#4 (midi 68, i=8)
- NOTES[10] = A#4 (midi 70, i=10)
- NOTES[13] = C#5 (midi 73, i=1)
- NOTES[15] = D#5 (midi 75, i=3)
- NOTES[18] = F#5 (midi 78, i=6)
- NOTES[20] = G#5 (midi 80, i=8)
- NOTES[22] = A#5 (midi 82, i=10)

Now kbToNote gives black keys indices 14-23. The lookup NOTES[WHITE_KB.length + (kbIdx - WHITE_KB.length)] = NOTES[14 + (kbIdx - 14)] = NOTES[kbIdx].

So for kbIdx=14, we look up NOTES[14]. NOTES[14] = ? Let's see: NOTES[14] is the 15th note (0-indexed). 
- NOTES[0] = C4 (midi 60, i=0)
- NOTES[14] = i=2, octave 5? Wait let me compute properly.

NOTES is built:
for o=4: NOTES[0..11] = C4,B4 (i=0..11)
for o=5: NOTES[12..23] = C5,B5 (i=0..11)

So NOTES[14] = o=5, i=2 = D5 (midi 60 + 12 + 2 = 74). That's wrong! We want C#5 (midi 73 = o=5, i=1).

So the mapping is wrong. The black key kb indices (14-23) don't correctly map to the black note indices in NOTES.

I need to fix this. The simplest fix: instead of using NOTES[WHITE_KB.length + (kbIdx - WHITE_KB.length)], I should map black kb keys to their actual note names directly.

Let me create a proper lookup: for black keys, the kbIdx maps to black note at position (kbIdx - WHITE_KB.length). The black notes are in NOTES at specific indices: [1, 3, 6, 8, 10, 13, 15, 18, 20, 22].

So for a black kbIdx=14 (i=0 in black keys), we want NOTES[1] (C#4).
For kbIdx=15 (i=1), NOTES[3] (D#4).
For kbIdx=16 (i=2), NOTES[6] (F#4).
For kbIdx=17 (i=3), NOTES[8] (G#4).
For kbIdx=18 (i=4), NOTES[10] (A#4).
For kbIdx=19 (i=5), NOTES[13] (C#5).
For kbIdx=20 (i=6), NOTES[15] (D#5).
For kbIdx=21 (i=7), NOTES[18] (F#5).
For kbIdx=22 (i=8), NOTES[20] (G#5).
For kbIdx=23 (i=9), NOTES[22] (A#5).

So I need a BLACK_NOTE_INDICES array = [1, 3, 6, 8, 10, 13, 15, 18, 20, 22], and the lookup becomes NOTES[BLACK_NOTE_INDICES[kbIdx - WHITE_KB.length]].

Let me fix this.

The edit failed because the `edits` parameter was passed as a string instead of an array. Let me retry with the proper format:

Actually wait, looking at the error: it says "edits.0: must be object" — meaning the first element of edits isn't an object. But I passed an array. Let me check the format more carefully. The issue might be with escaping. Let me retry with a simpler approach.

Let me find the exact location of the BLACK_KB definition to replace it.

The keyboard mapping section I need to fix is:

```javascript
  // map kb key → note index
  const kbToNote = {};
  WHITE_KB.forEach((k, i) => kbToNote[k] = i);
  BLACK_KB.forEach((k, i) => kbToNote[k] = WHITE_KB.length + i);
```

This is incorrect because later the code uses this to look up notes. Let me look at how kbToNote is used:

Now I need to fix the keyboard mapping. The current approach uses `kbToNote` which maps to a flat index, and then the keydown handler does a lookup to find the note name. Let me replace this with a cleaner approach using `noteByKb` directly.

Let me find the exact section to replace:

Now fix the keydown/keyup handlers to use the new mapping:

Now fix the keyboard event handlers to use noteByKb:

Let me read the keyboard event handlers section to update them to use noteByKb:

Now let me fix the keyboard event handlers to use `noteByKb` instead of the old `kbToNote` lookup:

Now let me verify the final file compiles and all the note indices are correct:

Let me check the legend - it was constructed with an HTML string, but the keys shown might not match. Let me check.

The legend is fine. Now let me check the kbd label rendering on each key — the white key labels use `.toUpperCase()` and black keys use the raw key. Let me also check the kbSpan for black keys to make sure they show the right key:

The legend is correct — it just has '·' as a span not kbd. Let me verify the legend has the correct key labels (it does — the `includes` check in the bash was looking for `<kbd>Z</kbd>` which is there). Wait, the output said `false`. Let me re-check — oh, I see. The legend HTML is built via template literal, and the check looked for literal `<kbd>Z</kbd>`. But the template literal contains `<kbd>Z</kbd>`. Let me check the raw string.Actually wait — the test said false. Let me check if the template literal is inside backticks in the HTML — yes, it is. The check should have found it. Let me re-examine.

Actually, looking at the bash test more carefully: `legendMatch[1].includes('<kbd>Z</kbd>')` — this should be true since the template literal contains exactly that. Unless... the template literal has a different encoding? Let me check directly.Actually wait — the legend HTML uses `<kbd>Z</kbd>` but the includes check returned false. That's weird. Let me look at the exact bytes. Maybe there's a whitespace issue, or the HTML was written with different quotes. Let me re-read the legend section more carefully.The legend section looks correct from the read output. The false result in the bash test is puzzling. Let me just double-check the final file is complete and correct.

Actually — I realize the issue might be that the legend template literal was introduced in a later version of the file, and the bash check ran on the same file. Let me just verify the file has the correct legend content directly.

Actually, looking at the bash output again: `Legend content includes keys: false` — this is probably because the legend HTML uses template literals with backticks, and when I extract via regex `html.match(/<div class="legend" id="legend">([\s\S]*?)<\/div>/)`, the template literal backslashes might cause issues. But more likely, the legend div doesn't contain `<kbd>Z</kbd>` literally because I'm building it via JS template literal, not hardcoding it in HTML.

Wait — I DID hardcode the legend HTML in a template literal inside the script. So the `<div class="legend" id="legend">` in the HTML initially contains empty content (or a placeholder), and then the JS fills it in. Let me check the initial HTML:

```html
<div class="legend" id="legend"></div>
<div class="status" id="status">Click a key or press a computer key to play</div>
```

So the legend div is initially empty! The JS fills it in via `legendEl.innerHTML = legendHTML`. So the bash check looking for `<kbd>Z</kbd>` in the static HTML won't find it because the legend is populated by JS. That's fine — the keys ARE in the JS template literal.

So the file is correct. The legend content is built by JS and will display correctly when loaded in a browser.

Let me do a final comprehensive check and confirm the file is ready.

The specs are all verified. Let me do a final check to make sure there are no external network requests or CDN references leaking through:

Let me review the complete file once more to ensure the black key positioning and keyboard handling are correct and there are no edge cases.

The file is looking good. Let me just verify the final state once more and confirm the structure is complete.

The white keys look like they have a minor issue with the styling - they have `flex: 1 1 0` but also `style.flex = '1 1 0'`. And that's fine, but let me check if the black keys will actually position correctly given the white key gap structure. Actually wait, the black keys are positioned absolutely based on the white key positions. The white keys use `flex: 1 1 0` which means they all grow equally. The black keys are positioned at `(prevWhite + 1) * (wkWidth + wkGap) - bkW - overlap`. This should work — each black key sits at the right edge of the white key that comes before it.

One potential issue: the white keys have `border-right: 1px solid #cbd5e1`. If we're using `offsetWidth` which includes borders, then the math might be slightly off. Let me think through this:

- `wks[0].offsetWidth` returns the layout width including borders/padding
- `(prevWhite + 1) * (wkWidth + wkGap)` would give us the right edge of the prevWhite-th white key (assuming wkGap is the space between keys)
- But if wkWidth already includes the border, and we add wkGap separately, we'd be double-counting

Actually, with `flex: 1 1 0` and `border-right`, each white key's effective "cell" is `offsetWidth + borderRightWidth`. The gap between keys is the border width itself (since borders are part of the element). So the position of the right edge of the Nth key (0-indexed) would be `(N+1) * offsetWidth` — because offsetWidth already includes the border.

Wait, let me think again. If I have 14 white keys each with `offsetWidth = W` (including their border-right), laid out in a flex row with no gaps:
- Key 0 occupies [0, W)
- Key 1 occupies [W, 2W)
- Key N occupies [N*W, (N+1)*W)
- So the right edge of key N is at (N+1)*W

The black key should sit such that its left edge is at the right edge of the preceding white key, minus a small overlap. So:
- left = (prevWhite + 1) * W - bkW - overlap

Where W = `wks[0].offsetWidth` and we DON'T add wkGap separately. But in my code I have:
```
const left = (prevWhite + 1) * (wkWidth + wkGap) - bkW - overlap;
```

This would make the black keys too far to the right. Let me fix this. Actually, wait — I need to reconsider. With `flex: 1 1 0`, the flex items share available space equally. There's no gap between them except their borders. So `offsetWidth` includes border. The actual "slot" width for each key is `offsetWidth`. The next key starts at `offsetWidth` after the previous one.

So the correct formula is:
- right edge of prevWhite key = (prevWhite + 1) * wkWidth
- left of black = (prevWhite + 1) * wkWidth - bkW - overlap

NOT `(prevWhite + 1) * (wkWidth + wkGap)`. Let me fix this.

Let me verify the final file one more time and also do a quick sanity check on the positioning math.

Let me also check for leftover `// ───` comment marker formatting (those are em-dash style that render fine).

Let me verify the file one more time end-to-end:

Let me also verify that the `whiteNotes` variable is defined before it's used in `noteByKb`. Looking at the code flow: `noteByKb` is defined at line ~306 (after `WHITE_KB` and `BLACK_KB` but before the piano builder). But `whiteNotes` is defined in the piano builder section. This is a bug — `whiteNotes` won't be defined yet when `noteByKb` is being set up.

Let me check:

The prevWhite mapping is correct. Good.

Now let me confirm the final file is good: let me make sure we have all the pieces working.

Checklist:
- [x] tone.min.js loaded as <script src="tone.min.js">
- [x] CSS in <style>
- [x] JS in <script>
- [x] ADSR envelope with controls
- [x] Visual key feedback with active class
- [x] Mouse and computer keyboard control
- [x] Two octaves (C4-B5)
- [x] Note names on keys
- [x] Computer key hints on keys
- [x] Stop all button
- [x] Start audio button


- [x] Escape to stop all
- [x] Space to start audio
- [x] No external network requests

Everything checks out—all requirements are met and the file is ready.