The user wants me to build a single-page web app with:
1. A clickable pentatonic pad grid that triggers synth sounds with reverb
2. A play/stop button that runs an arpeggiator sequence
3. Adjustable tempo for the arpeggiator
4. All sound synthesized (no audio files)
5. Using tone.min.js which is already in the current directory

Since I can't use external CDNs, I need to load tone.min.js from the local file. Let me first check if it exists and then build the app.

Pentatonic scales commonly used are:
- Major pentatonic: C, D, E, G, A
- Minor pentatonic: A, C, D, E, G

I'll create a 5x4 or 5x5 grid of pads, each triggering a different note from a pentatonic scale.

Let me build this step by step:
1. Create index.html with embedded CSS and JS
2. Use Tone.js for all the audio synthesis
3. Create reverb using Tone.Convolver with a generated impulse response (to keep it self-contained)
4. Create a synth using Tone.Synth or Tone.PolySynth
5. Create a 5x4 or 5x5 grid of pads
6. Implement play/stop button for arpeggiator
7. Add tempo control

Let me write this file.

I've created the index.html file with:
1. A 5x3 pentatonic pad grid using C major pentatonic scale (C, D, E, G, A across three octaves)
2. Clickable pads that trigger synth sounds with reverb
3. A play/stop button that runs an arpeggiator sequence
4. A tempo slider (60-240 BPM) that's fully functional
5. Keyboard support (1-5, q-t, a-g for the lower and upper octaves, spacebar for play/stop)
6. All sound synthesized using Tone.js (Triangle wave synth with envelope, reverb using generated impulse response)
7. No external dependencies - just loads tone.min.js from the local file

The app uses:
- Tone.PolySynth with triangle wave oscillators
- Tone.Reverb with a generated impulse response (to keep it self-contained)
- Tone.Sequence for the arpeggiator
- Keyboard mapping for quick access to different notes
- Visual feedback on active pads

The pentatonic scale used is C major pentatonic: C, D, E, G, A across three octaves (C3, D3, E3, G3, A3, C4, D4, E4, G4, A4, C5, D5, E5, G5, A5) - that's 15 notes which fits well in a 5x3 grid.