The user wants me to build a playable piano keyboard using the Tone.js library that's already provided. Let me plan this out:

1. Create a single index.html file with:
   - CSS in a <style> tag for styling the piano keyboard
   - JS in a <script> tag for the logic
   - Use the provided tone.min.js library

Features needed:
- Playable piano keyboard (visual keys)
- Mouse control (click to play)
- Computer keyboard control (keys mapped to notes)
- ADSR envelope for synthesized notes
- Visual key feedback (highlight when pressed)

Let me create a complete, self-contained piano app.

I'll map computer keys to piano notes. A common mapping is:
- Lower row (z, x, c, v, b, n, m) for white keys
- Upper row (s, d, g, h, j) for black keys

Or I could use:
- a, s, d, f, g, h, j, k for white keys (C4 to C5)
- w, e, t, y, u for black keys

Let me go with a common piano mapping:
- White keys: a, s, d, f, g, h, j, k, l, ; (C4 to E5)
- Black keys: w, e, t, y, u, o, p (C#4, D#4, F#4, G#4, A#4, C#5, D#5)

Actually, let me use a more standard mapping:
- Row 1 (white): a, s, d, f, g, h, j, k, l, ;, '
- Row above (black): w, e, t, y, u, o, p, ]

I'll create about 2 octaves (C4 to B5).

For Tone.js, I'll use:
- Tone.Synth with ADSR envelope
- Map keys to notes
- Visual feedback on key press/release

Let me build this now.

I've created a complete piano keyboard web app in a single index.html file. Let me verify it was created correctly.

I've created a complete, self-contained piano keyboard web application. Here's what it includes:

**Features:**
- **Visual Piano Keyboard**: 2 octaves (C4 to G5) with realistic white and black keys
- **Mouse Control**: Click and hold keys to play notes
- **Keyboard Control**: Computer keys mapped to piano notes (a-' for white keys, w,e,t,y,u,o,p,] for black keys)
- **ADSR Envelope**: Adjustable Attack, Decay, Sustain, and Release sliders
- **Waveform Selection**: Choose between Sine, Square, Sawtooth, and Triangle
- **Volume Control**: Adjustable master volume
- **Visual Feedback**: Keys highlight when pressed (red gradient)
- **Note Indicator**: Shows currently playing note in top-right corner
- **Touch Support**: Works on touch devices
- **Start Overlay**: Click to initialize audio context (required by browsers)

**Technical Details:**
- Uses Tone.js Synth with ADSR envelope
- All CSS inline in `<style>` tag
- All JS inline in `<script>` tag
- No external dependencies (except the provided tone.min.js)
- Beautiful dark gradient background
- Responsive and accessible design