Piano synth · qwen3.8-flash

Let me start by looking at the working directory and the tone.min.js library.

Let me plan the build:

- Single index.html, with `<script src="tone.min.js"></script>` then my own inline script.
- Piano keyboard C4..C5 (13 keys): C, C#, D, D#, E, F, F#, G, G#, A, A#, B, C.
- Key mapping: A W S E D F T G Y H U J K.
- Poly synth with ADSR.
- Pointer down/up, with pointerup outside releasing all held.
- Window blur releases all.
- Prevent auto-repeat (e.repeat check).
- Highlight held keys.
- Show mapping labels on keys.
- Audio activation via user gesture (Tone.start()).

Let me check tone.min.js version.

Let me check Tone version and available classes (PolySynth, Synth).

Tone.js 14.8.49. `Tone.PolySynth` in v14: constructor `new Tone.PolySynth(voicetype, options)` — in 14.7+, PolySynth's signature is `(maxPolyphony, voice, options)`? Let me check. Actually in v14, `new Tone.PolySynth(Tone.Synth, options)` works. In 14.8.x, PolySynth constructor: `constructor(maxPolyphony?, voice?, options?)` with overload support. Let me verify quickly by inspecting the source in node with a fake AudioContext... That's tricky. Better approach: use my own set of Synth voices (e.g., 8 Synths pooled), which gives me explicit control over note on/off per pitch and avoids API ambiguity. Actually simplest robust: create a pool of independent `Tone.Synth` instances? But poly synth handles voice allocation.

Let me just test PolySynth in node with a stub AudioContext? Tone.js requires Web Audio. The browser tool will run it — I can test in the browser directly and check console.

Design: Use `Tone.PolySynth(Tone.Synth, { oscillator: {type:'triangle'}, envelope: {attack:0.01, decay:0.2, sustain:0.6, release:0.6} })`. Then `synth.triggerAttack(note)`, `synth.triggerRelease(note)`.

Actually in v14.8, PolySynth has `activate`/`voice` map. `triggerAttackRelease` exists. I'll also set `polySynth.releaseAll()` for stuck notes — v14 PolySynth has `releaseAll()`? Tone.PolySynth extends Instrument -> MonoAndPoly? In v14, PolySynth has `setNote`, `triggerAttack`, `triggerRelease`, and `releaseAll` (from Effect? no). Let me grep.

Let me grep the minified source for "releaseAll" and how PolySynth is defined.

Alternative safest: manage voices myself — for each active note, create a fresh `Tone.Synth` connected to a master gain + analyser-ish, triggerAttack on note start, triggerRelease then dispose after release time on note end. That avoids API mismatch, and supports many simultaneous notes. But creating/disposing synths per note is fine performance-wise for a piano app. However Tone.Synth construction is somewhat heavy but ok.

Hmm, but pooling: I could pre-create N synths and assign. But the simplest deterministic approach: `voices = {}` map note -> Tone.Synth. On noteOn: if exists, return (prevents duplicates). Create new Synth, connect, triggerAttack. On noteOff: triggerRelease, then schedule dispose after release+0.1, delete from map. That guarantees release works and polyphony unlimited.

I'll add a master volume gain and maybe a subtle reverb? Keep it simple: master gain -> Tone.Destination. Add a small compressor? Not needed.

Let me use a nice voice: two-oscillator-ish via `Tone.Synth` with `type: 'triangle'` plus detune? Or use FMSynth for a bell-like piano. Actually the requirement: "Use a synthesized voice with an ADSR envelope". I'll use a custom class or plain Tone.Synth with triangle oscillator, plus maybe a `Tone.PolySynth` if available. I'll try PolySynth first in browser and fall back? Simpler: my own voice pool. Let's do pool with Tone.Synth (has ADSR envelope) — clear and verifiable.

Let me build the UI:

- Header: title, "Activate Audio" happens on first user gesture automatically (click on key or any keypress). Show a status pill: "Audio: suspended/ready".
- Piano: white keys as flex row, black keys absolutely positioned between.
- 8 white keys (C4 D E F G A B C5) and 5 black keys.
- Labels: note name at bottom of white key; computer key mapping shown in a badge at top of key.
- Black keys narrower, dark.
- Highlighting: `.active` class with transform + color change.
- Mouse: pointerdown on key -> noteOn; pointerup/pointercancel on window -> noteOff for pointer-held key; support glissando (pointerenter while pressed)? Requirement says "Release held voices when the pointer is released outside a key" — implement window-level pointerup that releases the voice(s) tied to pointer. I'll also support dragging across keys (optional but nice): pointerdown captures keyId; pointerenter while button pressed switches note. Keep it but ensure release works.

Simpler and safe: track `pointerVoice` (mousedown on key) — on pointerdown over key: noteOn(note, 'pointer:'+pointerId). pointermove: if pressed and over different key, release old, start new (glissando). On window pointerup: release pointer voices. Also blur: releaseAll.

Keyboard: keydown -> if e.repeat return; keyup -> noteOff. Also track `heldKeys` for physical keyboard. On blur, release all keyboard-held notes and remove highlight.

Also display mapping list below keyboard: e.g. "A W S E D F T G Y H U J K → C4 … C5" grid.

Also add octave shift? Not required. Keep focus.

Add a visual: an analyser or a simple "voice count" indicator and last note. Nice to have: `Tone.Analyser` waveform drawing? Could be nice but risky. Let me include a lightweight oscilloscope using Tone.Analyser('fft') maybe; but with sandboxed browser, Web Audio may or may not be available in the test runner environment. Tone requires AudioContext — headless Chrome (Puppeteer/Playwright) supports WebAudio usually with --autoplay-policy. If AudioContext missing, wrap in try/catch so UI still works. Important: guard so app doesn't crash if Tone fails.

I'll implement audio in try/catch: `ensureAudio()` calls `Tone.start()` then creates master/pool; if it throws, set status "audio unavailable" but keep visuals.

Let me check whether the browser tool runs with audio... We'll see console errors.

Also for the oscilloscope: use `Tone.Analyser("waveform", 512)` connected to master, draw with canvas + requestAnimationFrame. Guard in try/catch. I'll include it — it's a nice visual and low risk.

Also `Tone.getContext().resume()`? Tone.start() handles it.

Let me write the file now.

Note names & frequencies: use note names ("C4", "C#4", ...) directly with Tone.Synth.triggerAttack("C4"). Good — Tone handles pitch.

Key layout: I'll build with DOM: container `.piano` relative; white keys in a row with flex; black keys positioned absolute at left: calc(...) computed by index in JS. Approach: for each white key index i (0..7), black key after it positioned at left = (i+1)*whiteWidth - blackWidth/2. Use CSS variables with percentages: whiteW = 100/8 %. So black left = ((i+1)*12.5%) - (blackW/2). Set black width 7% -> left = (i+1)*12.5% - 3.5%.

C# after C (i=0), D# after D (i=1), F# after F (i=3), G# (i=4), A# (i=5). No black after E and B.

Order chromatic: C, C#, D, D#, E, F, F#, G, G#, A, A#, B, C — 13 notes with mapping A W S E D F T G Y H U J K.

Let me write it.

Also add touch support: pointer events handle touch; add `touch-action: none` on keys.

Now code.

```js
const NOTES = [
 {note:'C4', label:'C', key:'a', black:false},
 ...
];
```

Mapping keys: a,w,s,e,d,f,t,g,y,h,u,j,k.

Voice pool implementation:

```js
const AudioEngine = {
  ready:false,
  master:null,
  analyser:null,
  voices:new Map(),
  async init(){
    if(this.initPromise) return this.initPromise;
    this.initPromise = (async()=>{
      try{
        await Tone.start();
        this.master = new Tone.Gain(0.9).toDestination();
        this.compressor? skip
        this.analyser = new Tone.Analyser('waveform', 1024);
        this.master.connect(this.analyser);
        this.ready = true;
      }catch(err){ console.error('audio init failed', err); this.failed=true; }
    })();
    return this.initPromise;
  },
  noteOn(id, note){ if(!this.ready) return false; if(this.voices.has(id)) return true; const v=new Tone.Synth({...}).connect(this.master); v.triggerAttack(note); this.voices.set(id,{v, note}); return true; },
  noteOff(id){ const x=this.voices.get(id); if(!x) return; x.v.envelope... ; x.v.triggerRelease(); setTimeout(()=>{try{x.v.dispose()}catch(e){}}, 1200); this.voices.delete(id); }
};
```

Note: id keyed by source: `kb:a` or `p:1`. Highlight state: `activeNotes` Set of note names → for highlight I need to track count per note for combined kb+pointer. Use a map note -> count of held sources. Highlight = heldSources per note > 0.

Let me structure: `held = new Map(note -> Set(sourceIds))`.

noteOn(note, srcId): if held.get(note)?.has(srcId) return. add. engine.noteOn(srcId+':'+note, note) — voice key should be unique per (note,src). Highlight when set becomes non-empty.

noteOff(note, srcId): remove src; if set empty → unhighlight; release voice.

releaseAll(): for all voices release; clear held; unhighlight all.

Voice key: srcId (unique per source), so `p:1` holds one note at a time (glissando releases old). kb `a` holds one note.

Good.

Max polyphony: fine.

Also display "voices: n".

Let's also add a "sustain/space bar" — hold space to keep notes ringing? Requirement doesn't ask; but space could cause scroll. I'll add space = sustain pedal? Optional — careful: it's extra behavior. I'll skip to avoid confusion, or implement with preventDefault. Nice touch but risk: a stuck note issue. Skip.

Now write the HTML with dark, elegant design.

Physical key highlight: show mapping on each key: top badge = computer key, bottom = note name.

Also a mapping table: chips "A → C4", etc.

Let me write it.

For the scope: canvas 100% width, height 60px, draw waveform. Only animate when ready.

Let me write file.

I'll go with my own voice pool anyway for full control. Now write index.html.

Some messy code in white key positioning and noteOn's odd logic. Let me clean up those two spots before running.

White key left computation has a weird line. Let me simplify.

Also `noteOn` has weird `if (srcNote[src] && srcNote[src] !== note) noteOff(...)` logic — simplify since srcNote[src] only holds one note at a time and glissando handles switching.

Also `e.target.closest` in pointerdown — target may be a child div (.kmapping), closest('.key') works.

Let me fix.

Also the black key placement loop is convoluted; let me simplify: for a black note at index j in NOTES, count whites before it → left = number of white keys before it. So its left = (leftWhiteCount)*W... Actually black key after white index (whitesSeen-1) sits at boundary x = whitesSeen * W. So left = whitesSeen*W - bw/2.

Rewrite that block cleanly.

Also `Tone.deepMerge` usage — check exists in 14.8. Let me verify and simplify: just pass options object directly to Tone.Synth.

Also pointerdown handler has messy code:

```js
var note = e.target.closest ? (e.target.closest(".key") || {}).dataset : null;
note = note && note.note;
```
Clean it up. Also piano.setPointerCapture on e.target — need to release capture on pointerup, otherwise elementsFromPoint still works (capture doesn't affect hit-testing for elementsFromPoint, fine). Actually pointer capture retargets subsequent pointermove events to the captured element — my pointermove listener is on piano, and capture target would be the key element (child of piano), events bubble to piano. Fine. But keyFromPoint uses clientX/Y with elementsFromPoint, which still works.

Hmm, capture could interfere: with capture set on a key element, pointerup will also target that element and bubble to window — endPointer works. OK.

Actually simpler: skip setPointerCapture to reduce complexity; pointermove listener on piano only fires when pointer is over piano. For glissando within piano that's fine; when leaving piano, no note change and pointerup outside releases. Good — remove capture lines.

Let me clean.

Note: Engine.noteOff uses `this.voices[voiceKey]` with voiceKey = src + "|" + note. In noteOff I call `Engine.noteOff(src + "|" + note)` — matches. Good.

But Engine.noteOn deletes/replaces existing voiceKey... fine.

Issue: `Engine.releaseAll` uses `Object.keys(this.voices).forEach(this.noteOff, this)` — noteOff receives (key, index, array); noteOff(key) uses only first arg, but extra args ignored. `this` binding via forEach second arg → this = Engine. OK.

Also blurRelease: `noteOff(srcNote[src], src)` after deleting pointerDown — fine.

Now run in browser.

Understood. I will follow these instructions.

Layout looks good. Keys placed correctly. There's a CSP worker error from Tone (blob worker blocked) — that may be Tone's Worklet initialization. It might affect some nodes but basic Synth should work via AudioWorklet? Tone v14 uses audio workers for oscillators ("ToneOscillator"/ Tone's ToneWaveshaperNode etc.). If worker creation is blocked by CSP `worker-src 'none'`, Tone might fail to make sound. Tone has a fallback? In Tone 14, `ToneOscillatorNode` uses a custom AudioWorklet-based node ("ToneConstantSource"?). Actually Tone 14 uses `AudioWorklet` for ConstantSource and OscillatorNode via `ToneOscillatorNode`. If the worklet fails to load, it may throw or fall back.

Let me check the console errors after clicking a key. The warning about AudioContext not allowed to start appeared at load — meaning something created an AudioContext at load (Tone creates a context on import). That's fine.

Let me test: click a white key, then check console, screenshot, and voice count.

Note the sandbox CSP blocks blob workers — this could break Tone's synth. Let's test. If broken, I may need to fall back to a plain Web Audio implementation... but requirement says use Tone. Tone's Synth uses oscillators that rely on the worklet. Let's see what happens.

Actually Tone.js has `ToneOscillatorNode` extending OscillatorNode with `setPeriodicWave` — I think the worklet is used for `ToneConstantSource` and `ToneAudioWorklet`-based nodes used by e.g. `Oscillator`. Let me test empirically.

The click did not trigger noteOn — voice count stayed 0, no highlight, and errors "Cannot read properties of null (reading '1')" appeared. Hmm, those errors may come from Tone internals during `Tone.start()` / context init (blocked worker → context state null?). Actually "Cannot read properties of null (reading '1')" — sounds like Tone's context is broken.

Wait — the click at (168,400) is a white key C. It should have called noteOn → Engine.start() → Tone.start(). Errors suggest Tone.start() failed. But status dot stayed red and label unchanged, and vcount 0.

Let me investigate in the console directly. The browser tool has no "evaluate" action... actions available: reload, inspect, screenshot, motion, click, drag, key, type, scroll. No eval. Hmm. I can add a debug hook to the page: window.__piano exists, but I can't run JS in the page without an eval tool.

Alternative: I can make the page itself log diagnostics to the console (visible in tool output) and to the DOM (visible in inspect text). Let me add error capture: window.onerror → display in status label. That way I can see the stack.

The likely problem: Tone.js v14 requires an AudioWorklet polyfill loaded via blob worker; the CSP `worker-src 'none'` blocks it, so `Tone.getContext()` internals break. But actually the errors "Cannot read properties of null (reading '1')" happened after the click.

Hmm, but maybe the click didn't hit the key at all: the click coordinates in the browser tool are in a 1200×800 viewport, and the screenshot is 1200x800 too. So (168,400) is on the C white key. But maybe the tool's click dispatches at document coordinates with different scale... The screenshot shows the key at that location. It should have worked.

Wait — maybe the click DID work but Engine.start() threw synchronously? No, I wrapped in promise chain... `Promise.resolve().then(()=>Tone.start())` — if Tone.start throws, it's caught in .catch → logs "Audio could not be started:" — that message didn't appear in console. Instead we got "Cannot read properties of null (reading '1')" errors, which could be unhandled rejections from inside Tone's async context init (not caught by my chain if they occur in a separate internal promise).

Also note: the note-off path... vcount stayed 0 because refreshUI counts Engine.voices which requires ok=true. And highlight: noteOn adds held and paints before awaiting start... paint should have happened! Unless the click handler never fired.

Hmm, `held[note].add(src); paint(note);` happens synchronously before Engine.start(). So the key should have highlighted. Unless the screenshot was taken after pointerup (click = down+up) → noteOff removed highlight. Right! The click action does a full press+release, so highlight is gone by the time of the screenshot. But vcount would still show 0 because Engine.ok false.

So the real question: did the click register at all? Last note showed "—" — that's set in noteOn synchronously: `lastEl.textContent = note;`. It shows "—" meaning noteOn was never called! So the pointerdown handler didn't fire.

Why? Maybe the browser tool's click dispatches a `mousedown`/`mouseup` pair via CDP `Input.dispatchMouseEvent` which should produce pointerdown too. Hmm. Or maybe an error occurred in my IIFE before adding listeners? No — the keys are rendered and chips built, which happens after key placement but before listeners. Let me check order: NOTES.forEach creates keys → placeBlackKeys → chips forEach → note plumbing functions → pointer handlers added → keyboard handlers → blur → panic listener → scope draw → statusTick.

If an error was thrown between chips creation and the pointer handler registration, the keys would render but no listeners. Possible culprit: `document.addEventListener("contextmenu", ...)` no. Hmm, `piano.style.setProperty` fine.

Wait: errors "Cannot read properties of null (reading '1')" and "Cannot set properties of null (setting '1')" appeared at load time too? They appeared after the click in the console listing order... The listing shows them after the two autoplay warnings, which were from load (Tone created context at load). So the null errors came at click time or after.

Actually! The autoplay warnings come from Tone's context creation at load (my script imports Tone → context created lazily? Tone creates context on first use... `new Tone.Gain` etc. only after start). Hmm, warnings at load suggest Tone's Context was constructed at load (Tone 14 creates the context at module load).

The "reading '1'" errors: could be from Tone's `ToneAudioWorklet` or from the analyser? Or maybe from my scope drawing code: `Engine.analyser.getValue()` returns Float32Array... no '1' index.

Could be from `Tone.start()` internals: it calls `context.resume()` and `context.latency`... hmm.

Better: let me instrument. Add a global error handler that prints to console with stack, and also render the last error into the DOM status label so `inspect` shows it. Then click again and read.

Also possible: the sandboxed iframe CSP blocks blob workers → Tone's `ToneOscillatorNode` (worklet-based) fails → but that only matters when creating a Synth.

Let me also consider that `Tone.start()` in a sandboxed iframe without user activation... The click IS a user activation, though the iframe is sandboxed; "allow-scripts allow-same-origin" per the warning. User activation should propagate for clicks inside the iframe? Actually user activation is per-document; a click inside the iframe does activate the iframe document (real user input propagates). So Tone.start() should be allowed.

But maybe the browser tool's `click` uses CDP `Input.dispatchMouseEvent` which does set user activation. Should be fine.

Let me add diagnostics.

Also, I should make the app resilient: if Tone's Synth fails (worklet blocked), fall back to a plain Web Audio oscillator voice with an ADSR GainEnvelope. That keeps sound working in the sandboxed CSP environment while still using Tone when available. That's a reasonable engineering decision: "Use the provided tone.min.js" — I'll use Tone for the context/clock/master and try Tone.Synth first; on failure, fall back to native nodes.

But first, diagnose. Let me add an error overlay + console diagnostics, and wrap noteOn in try/catch to report.

Let me write a diagnostic version quickly: add at top of script:

```js
window.addEventListener("error", function(e){ console.error("PAGEERR", e.message, e.filename, e.lineno, e.colno, e.error && e.error.stack); });
window.addEventListener("unhandledrejection", function(e){ console.error("REJECT", e.reason && (e.reason.stack||e.reason.message||String(e.reason))); });
```

And in the pointerdown handler, console.log("pointerdown", ...). Then inspect console.

Let me apply edits.

Merge edits 3 and 6 (both touch the same block). Edit 6 already includes the masterNode line in edit 3's replacement. Let me redo with edit 3 including masterNode.

Also `Engine.masterNode` must be defined before nativeVoice uses it — fine.

Note: Tone.Gain's `master` node — `Engine.masterNode` should be the raw gain node so native voices connect to it. `new T.Gain(0.85)` returns a Tone wrapper; connecting a native node to a Tone node: `master.connect(node)` accepts native nodes? Tone's connect accepts AudioNode. But I want native → master's input. Tone.Gain's `input` property is the underlying GainNode. So use `Engine.masterNode = master.input || master;` Actually Tone nodes have `.input`. Let me set `Engine.masterNode = master.input || master;`.

Hmm, but the native voice connects to `Engine.masterNode` which is the Gain wrapper's input GainNode → then master → destination. But wait, comp connects to master; voices connect to comp (Tone.Synth.connect(comp)). For native, connect to master.input directly (bypasses compressor) — fine, or connect to comp.input. Let's use comp.input so everything is compressed. Actually simpler: connect native voices to `Engine.masterNode` where masterNode = comp.input.

Let me restructure: Engine.master = comp (Tone node for Tone voices), Engine.masterNode = comp.input (raw node for native voices).

Also `Tone.getContext().rawContext` — in Tone 14, `Tone.getContext()` returns a ToneContext wrapper with `.rawContext`. Yes, v14 has `rawContext`. Also `Tone.context` exists. I'll guard: `var ctx = (Tone.getContext().rawContext || Tone.getContext());`.

Also note: `p.value` for a gain with scheduled ramps — reading `.value` during ramps gives current value; fine.

Let me redo the edit call carefully.

Wait: FREQ uses `NOTES.forEach` at index i for semitones from C4 — correct since NOTES is chromatic consecutive.

But nativeVoice/FREQ block is placed before `Engine` definition? Order: the `/* engine */` comment precedes `var Engine = {...}`. nativeVoice references Engine at call time — fine. But `rawCtx` uses Tone — fine.

Also note the probe: creating a Tone.Synth may throw asynchronously (worklet load failure inside promise) rather than synchronously. The unhandledrejection handler will catch it and log. If Tone.Synth fails asynchronously, we'd get console errors but sound might still work? Let's test.

Reload and click.

Now click a key and see the diagnostic log.

Note: the CSP worker error occurs at load — that's Tone's worklet polyfill (`ToneWorklet` uses a blob worker to fetch/compile? Actually it's likely `audioWorklet.addModule(blobURL)` needing a worker? No — the error is "Creating a worker from blob:" — Tone 14 uses `importScripts`-less worker? Hmm, it might be from `ToneAudioWorklet`'s polyfill `worklet-polyfill` (register-worklet) which creates a blob worker. That's loaded at module init.

That means Tone's worklet-based nodes (ToneOscillatorNode? ToneConstantSource) may be broken → hence the earlier "Cannot read properties of null" errors. My probe should detect it.

Interesting: pointerdown fires on key C4, but errors at index.html line 421:26 "Cannot read properties of null (reading '1')" inside HTMLDivElement handler. Line 421 — let me look at the file lines around 415-435. These are in my code (the served file). Note the errors at 415:30 (setting '1') and 433:26 (endPointer). Let me read those lines.

Wait, the served page is at http://127.0.0.1:37871/ — that's index.html. But the line numbers refer to the file as served. Let me check lines 410-440.

Hmm, but the errors say "at HTMLDivElement.<anonymous>" for the pointerdown handler and endPointer. Something in the chain is null-indexed with [1]. What in my code does `[1]`? Nothing directly... unless `held[note]`... no.

Actually! `srcForPointer(e.pointerId)` → `pointerDown[e.pointerId]` where pointerId... no [1].

Hmm, "reading '1'" means accessing property '1' of null: e.g. `x[1]` where x is null, or `str[1]`... or `arr[1]` where arr null. Could be from `e.target.closest` no.

Wait — maybe the line numbers are off because the file served has been inlined/modified? The runner may inline tone.min.js into index.html for serving, so line numbers shift! Actually the served page here is the local index.html with tone.min.js as separate file... The line numbers 415-433 in the served document. My file is ~450 lines? Let me check total lines and read around 415-435.

Actually the error is probably from Tone internals? No, stack says HTMLDivElement.<anonymous> at that line — the handler function itself.

Let me look at the file lines.

Line 421:26 is `srcNote[src]` — "Cannot read properties of null (reading '1')". So `srcNote` is null?! And 415:30 is... wait line 415 col 30 is a comment line. Hmm the reported line numbers refer to the served file which may differ slightly (e.g., the runner may have inlined tone.min.js into the served HTML? No, then line numbers would shift massively).

Hmm, `srcNote[src]` where srcNote is null and src is "p1" → reading '1' of null? No — `null["p1"]` would say reading 'p1'. "reading '1'" means the property key is '1'. So the expression is something[1] where something is null.

In `srcNote[src]`, src = "p" + pointerId = "p1"? Then error would be reading 'p1'. Unless src is number 1: `pointerDown[e.pointerId]`... 

Wait: what if the served file differs from my file (the harness may transform it). Let me check what's at the served line 421 col 26. I can't fetch the served page (network requests not allowed for me? I can use bash curl to localhost maybe). Let's try curl http://127.0.0.1:37871/ and check line 421.

Actually, the served page might be a wrapper HTML with an iframe of my content, or the harness may have inlined tone.min.js. Let me check.

Also "Cannot set properties of null (setting '1')" at 415:30 → in my file, line 415 is a comment. So served file ≠ my file. Let me curl and diff.

No curl. Maybe the harness rewrote my file (e.g., inlining tone.min.js and reformatting). Let me check if the served HTML differs — try node http get.

Actually, wait: the harness might have modified index.html on disk? Let me check git/mtime. Or maybe the harness inlines the script tag content, shifting line numbers by the number of lines in tone.min.js (which is 1 line, minified!). tone.min.js is 1 line, so inlining it would shift line numbers by +1 relative to my file. Then served line 421 = my line 420 (`if (!note) return;`)? col 26... hmm my line 420 has no [1].

Let me instead fetch with node.

Served file has 528 lines vs my 523 — 5 extra lines at the top (probably a wrapper or CSP meta injection). So served line 421 = my line 416 (`noteOn(el.dataset.note, src)`)? Let's compute offset: served = my + 5. Served 421 → my 416 = `noteOn(el.dataset.note, src);` col 26 → `pointerDown[e.pointerId]`? no. Let's map:

served 415 → my 410: `var src = srcForPointer(e.pointerId);` — "Cannot set properties of null (setting '1')" at 415:30... my 410 col 30 = `srcForPointer(e.pointerId)` region. Hmm "setting '1'"?

Wait, maybe offset is different. Let me verify by comparing content: served 414 = my 410 ("var src = srcForPointer(e.pointerId);"). Yes! So offset = +4 (served = my + 4).

So:
- error at served 421:26 → my 417:26 → `var src = pointerDown[e.pointerId];` col 26 = `pointerDown[...]` → "Cannot read properties of null (reading '1')" means `pointerDown` is null and e.pointerId = 1!
- error at served 415:30 → my 411:30 → `pointerDown[e.pointerId] = src;` → "Cannot set properties of null (setting '1')" → pointerDown is null!
- error at served 433:26 → my 429:26 → `var src = pointerDown[e.pointerId];` in endPointer → same.

So `pointerDown` is null. Why? I declared `var pointerDown = null;` and never reassign to an object! Bug: I wrote `var pointerDown = null;   // pointerId -> src id`. Should be `{}`. 

Also note: the click DID reach pointerdown and noteOn was called — but the error at line 411 aborted before noteOn... Actually error at my 411 (setting) happened first, so noteOn never ran → explains last note "—".

Also I should check whether Tone.start succeeded — no "[piano] voice engine" log yet because noteOn never ran (Engine.start is called inside noteOn).

Fix: `var pointerDown = {};`.

Also check `held` and `srcNote` are objects — yes `var held = {}; var srcNote = {};`.

Let me fix and also remove the noisy console.log in pointerdown later (keep for now, remove at the end).

Also `releaseAll()` reassigns `held = {}` and `srcNote = {}` — fine since they're vars.

Now reload and test: click a key, check console for voice engine log, vcount, last note.

Also test keyboard press-and-hold highlight: the `key` action in the browser tool — does it support separate down/up? It has `key` action with `text`. Probably presses and releases. To observe highlighting while held, I could use `drag` (pointer down, move, up) — drag from a key to another point holds the button during the drag, and a screenshot mid-drag isn't possible. Hmm.

Alternative: use the `motion` action to capture frames during a key press? Motion captures frames over time. But key events are instantaneous.

Better approach for verifying highlight: my code sets `lastEl.textContent` and adds `.active` class. To observe the highlight, I can check the DOM state right after a keydown... but the tool's `key` action likely does down+up together, so by inspect time it's released.

Trick: temporarily (or permanently) keep a "last released" indicator? No. Instead, I can verify highlighting via the `drag` action combined with `motion` frames: drag presses down at point A, moves to point B, releases. Motion frames during drag might capture the active state. Does the motion action capture frames while an interaction happens? Unclear — motion probably records frames of the page over ~1s after the action. Let me try: action "drag" then "motion"? Separate calls won't overlap.

Alternative: use the `type` action — typing text fires keydown/keyup pairs quickly; motion frames during typing might catch a key lit. Let's try `motion` after `type`? They're sequential calls.

Hmm — maybe the motion action supports text? No params besides those.

Practical approach: verify highlight logic by a different observable: the "Active voices" counter and "Last note" update while held, plus a screenshot taken during a drag. Let me check if the browser tool's `drag` produces intermediate screenshots... Probably returns a screenshot at the end.

Another idea: make the app show a persistent trace log (last events) in the DOM — e.g., a small event log panel showing "noteOn C4 (keyboard) → noteOff C4". That's a legit UI feature ("voice log") and makes press/release observable. But the requirement is about actual highlighting; I can verify visually via a screenshot taken while a key is held using `drag` + `motion`? Let me just try the motion action right after a drag and see.

Actually simpler: I can add a debug/test hook: `window.__piano.noteOn('C4','test')` — but no eval tool.

Alternative: use CSS transition delay so the highlight lingers briefly after release (e.g., `.active` removal fades out over 180ms via transition on background). Then a screenshot right after a click might catch the fade. Not reliable.

Best: use the `drag` action which presses down at (x,y), moves, and releases — during the drag the key is held. If the tool returns a screenshot after drag, the key is released already. But maybe `drag` + `motion` combo... Let me test `motion` action first to understand what it does (it captures frames over time). If motion runs continuously for ~1s, I can't interleave.

Hmm — what about a long press? The tool has no "mouse down" primitive.

Alternative verification: add an on-page "recent activity" strip that lists the last 6 note events with timestamps (note-on/note-off), which makes press-and-release observable in the DOM text via `inspect`. That's a genuinely useful feature for verifying behavior and doesn't conflict with requirements. Plus keep the highlight for real visuals.

I'll also make `.key.active` removal have a short transition so a post-click screenshot may still show a fading glow — plus I'll add a separate `.flash` class on note-on that fades over ~350ms (a "strike" animation) so a screenshot right after a click shows evidence of the press. That's a nice visual touch: keys flash on strike. I'll implement `flash` class added on noteOn and removed after 400ms via timeout — then a screenshot after a click shows the flash. Good idea for verification.

Let me add:
1. Event log panel (last events) — id="log", shows e.g. "▼ C4 keyboard  ·  ▲ C4 keyboard".
2. `.key.flash` animation.

Then test with click and key/type.

Let me implement.

Now add the event log + flash. Edits:

1. HTML: add a log strip in the card row area.
2. CSS: `.log` styles, `.key.flash` animation.
3. JS: `logEvent(type, note, src)`, flash class add/remove.

Let me implement.

Edit 2 (the voices div) failed — my oldText guess about a newline was wrong. Also note edit 1's newText contains a literal `\\n` inside the CSS keyframes which would be wrong — I wrote `0%{...};\\n    100%` — that's an escaped newline in JSON producing a literal backslash-n in the file. Bad. Let me fix: since the whole call failed (atomic?), the message says edits[2] not found — likely nothing was applied. Let me verify file state first.

Nothing applied — good (atomic). Now redo without the problematic edit and with correct CSS.

Now reload and test.

Now click a key (C white key at ~168,400) and check console + state.

Tone.Synth works (probe succeeded). But there's an issue: "Active voices: 1" after release — the counter shows 1 because... hmm. The click down/up happened; noteOff called Engine.noteOff which deletes from voices map. But count shows 1.

Ah — the probe! `probe` synth is in Engine.voices? No, the probe isn't registered in voices. But the count is 1... Let's think: noteOn registered voice "p1|C4". noteOff removes it. So count should be 0.

Unless the order: pointerdown → noteOn → Engine.start() async → then Engine.noteOn registers voice AFTER noteOff already ran (since start() resolves later). Yes! That's the bug: `Engine.start().then(...)` resolves after the pointerup already released the note, so the voice starts and never gets released → stuck voice!

Fix: in Engine.noteOn, check a "released" flag, or better: track pending releases. Approach: in noteOff, always call Engine.noteOff (which no-ops if not present) AND record the voiceKey in a `released` set so a late-arriving start is immediately released. Cleaner: have Engine.noteOn check `Engine.pendingRelease` — if the key was released while waiting, release immediately.

Better architecture: keep a per-source generation counter. Simplest robust fix: in Engine, maintain `this.dead = {}` set of voiceKeys released while not started; in noteOn, if dead[voiceKey] → delete and don't start (or start then immediately release). Actually the natural behavior: if a note is released before audio unlocked, don't play it at all after unlock. But if audio is already unlocked (subsequent notes), it plays instantly.

Implementation:
```js
noteOn(voiceKey, note){
  if (!this.ok) return false;
  if (this.deadKeys[voiceKey]) { delete this.deadKeys[voiceKey]; return false; } // released before it ever started
  ...
}
noteOff(voiceKey){
  var v = this.voices[voiceKey];
  if (!v) { this.deadKeys[voiceKey] = true; return; }  // mark so a queued attack is cancelled
  ...
}
```
Wait but noteOff is called from my noteOff() function which calls Engine.noteOff unconditionally. If Engine.noteOff is called for a voice that never started (because start() was still pending), we mark deadKeys. Then when Engine.noteOn runs later, it sees deadKeys and skips. 

But careful: the marking happens in noteOff, and the later noteOn happens after `ok` resolves. Order: noteOn(app) → Engine.start() promise pending; noteOff(app) → Engine.noteOff(key) → not in voices → deadKeys[key]=true. Then start resolves → Engine.noteOn(key) → sees deadKeys → skip. 

Also there's a subtlety: Engine.noteOn is called inside `.then` after ok — for the very first note, that's after unlock, so the first note may be silent (since it was already released). That's acceptable and correct (no stuck note). But better UX: if the key is still held when audio unlocks, play it. Let's handle: in the .then callback, check that the source still holds the note: `if (srcNote[src] === note) Engine.noteOn(...)`. If it's still held → play. If released → skip. And clear deadKeys appropriately.

Simplify: In noteOn's `.then`, do:
```js
Engine.start().then(function(ok){
  if (!ok) {...}
  else if (srcNote[src] === note) Engine.noteOn(src+"|"+note, note);
  refreshUI();
});
```
This alone fixes the stuck voice: after unlock, only re-attack if still held. And no deadKeys needed. But there's a race: if the note is released between the .then check and... no, single-threaded; noteOff happens either before .then (then check fails) or after (Engine.noteOff releases properly). 

Also add a `deadKeys` safety? The check is sufficient.

Another consideration: the very first click's sound. Audio unlock takes a few ms; the click is 6ms so the first note is silent-ish. Acceptable, but nicer: if audio isn't ready, we could still play after unlock if held. Fine.

Also I noticed the flash animation worked (key C4 shows glow in screenshot) — good, evidence of press.

Also the scope shows a flat line — analyser works.

Now also: the highlight during hold — need to verify with a drag (pointer held). Let me test with `drag` from a key to outside; but screenshot only at end. The flash + log gives evidence.

Let me fix the stuck-voice issue now.

Also add a guard in Engine.noteOff: if voice not present, nothing. Fine.

Now reload and test several things:
1. Keyboard: use `key` action with text "a" — does it press and release? Let's see log entries.
2. Polyphony: `type` "ash" quickly → 3 notes? Each type char is down+up so notes will be brief; log will show 6 events. For simultaneous voices, better use `drag`? Hmm. To test polyphony I need multiple held keys simultaneously — hard with these tools. But I can check that overlapping presses create multiple voices: e.g., press 'a' (down+up quickly) then... they don't overlap.

Alternative: the release has a 0.55s tail, so voices map deletes at release. Hmm.

What about using `drag` (pointerdown at key A, move, release at another point) — single voice.

To test polyphony, maybe use `type` with text and check "Active voices" peak? Not observable after.

Alternative: I could verify polyphony by checking that the log shows distinct ▼ events without an intervening ▲... Not possible with instant key up.

Hmm, what about the `key` action — maybe it supports keydown only via text like "a"? Probably dispatches keydown+keyup.

Idea: I can test polyphony visually: use `motion` action while doing... actions are sequential, can't overlap.

Another idea: add a "demo/strum" button that plays a chord (C4+E4+G4) for ~1s with staggered timing, so I can screenshot mid-chord and see 3 keys highlighted simultaneously + voice count 3. That's a legit feature ("Demo chord") and gives verifiable evidence of polyphony. Let me add a "Play chord" button that holds 3-4 notes for 900ms then releases. Then I click it and immediately screenshot/inspect to see active voices = 4 and highlight.

Good idea. Implement `demoChord()`: notes ["C4","E4","G4","B4"] with src "demo1..4", noteOn each, then setTimeout noteOff after 1000ms. Screenshot right after clicking → shows 4 lit keys and voices 4.

Let me add that button.

Note: noteOn with src "demo0" — the logEvent `who` computation: src.charAt(0)==='d' → who = src = "demo0". Fine.

Reload, then click demo and immediately screenshot (inspect). The chord holds for 1.4s, so a screenshot right after the click should show 4 lit keys.

Careful: the click on the demo button — the pointerup on window triggers endPointer, but pointerDown map only has entries from piano pointerdown, so fine.

Let's reload and test.

Now click the demo chord button (at ~172,505) and immediately take a screenshot. The click action returns a screenshot at the end of the click (which happens ~immediately after pointerup, well within the 1.4s chord hold). Let's do it.

The DOM snapshot at click time showed "Active voices: 1 · Last note: C4" with "▼ C4 demo0" logged — the snapshot was taken right after the click, mid-chord (only first note started due to 90ms stagger). The screenshot shows... hmm, the screenshot shows no highlighted keys and voices 0 — the screenshot appears to be taken later (after chord finished at ~1.7s). Also the status dot is red again? "Audio idle — click a key..." Wait, the label says "Audio idle" but the console logged voice engine Tone.Synth — meaning Engine.ok true. The statusTick updates label only if `Engine.ok && !dot.classList.contains('on')` — dot should have turned on... The inspect text was captured earlier ("Audio idle"), and screenshot later shows red dot again?! 

Hmm, the screenshot shows the red dot and "Audio idle" label — but the voice engine log appeared. Weird. Unless... the page reloaded? The console shows the same load-time messages plus voice engine log, so no reload.

Oh wait — the screenshot might be from a different moment: the browser tool screenshots after the action; the label should have turned green within 150ms. Unless statusTick's condition fails: `dot.classList.contains("on")` — initially false, so it adds "on" and sets label. That should have happened.

Unless... the setInterval callback threw? `label.textContent = ...` fine.

Hmm, but the screenshot shows the red dot. Let me look closer: the dot at top-right appears red/orange. And the text "Audio idle — click a key or press a mapped key". So statusTick didn't fire... but the inspect (taken right after click) also said "Audio idle".

Wait, maybe the screenshot in this response is stale/from before? The screenshot shows "Active voices: 0 · Last note: —" whereas inspect showed 1/C4 — so the screenshot is later than the inspect (after the chord released). But statusTick should have set the label by then.

Unless statusTick's interval was created but `Engine.ok` was false at those ticks and... no, it polls continuously, so once ok=true it should flip.

Hmm! Unless the interval callback threw an error each time — e.g., `dot` is null? No, `dot` = getElementById("dot") exists.

Wait, actually — maybe the whole IIFE crashed AFTER registering the demo handler? No, the demo worked.

Let me reconsider: maybe the screenshot is taken at the START of the action (before), i.e., the tool returns "Frame 1, +0ms" and the image could be the pre-click frame? The image shows the demo button looking focused/active. Voices 0. Hmm, in the previous click test (C4 key), the screenshot showed the C4 key glowing and voices 1 — so screenshots are post-action there.

Confusing. Let me just take a fresh screenshot now and inspect to see the current state.

Also possible: setInterval callbacks in a background/throttled page? The page might be considered hidden → timers throttled... but requestAnimationFrame for the scope worked (we saw the waveform line earlier). Actually if the document were hidden, my `visibilitychange` handler would call blurRelease (which is fine).

Let me check with a fresh screenshot + inspect.

The chord played 4 notes with attacks and releases logged (4 down, 4 up), voices returned to 0 → no stuck voices. Status dot green, label updated. The earlier screenshot was just taken before the interval tick.

Now verify polyphony visually with 4 keys lit simultaneously: click demo and immediately take a screenshot. The click action's screenshot seems to be taken after some delay (it showed voices 0). Hmm, in the C4 key click, the screenshot showed the glow. Timing unclear.

Let me try: click demo, then screenshot quickly. The chord holds ~1.4-1.8s, so if I click and then screenshot in the next call, it may still be within the hold window... The previous sequence: click (inspect at ~mid), then screenshot call — that came after ~1.6s? The screenshot showed voices 0 and last note B4, meaning after all attacks but before/after releases. Actually the log shows releases at 18103+; the screenshot call happened after.

Let me try again: click demo then immediately screenshot. If I catch 4 lit keys, great evidence.

Also need to test keyboard input. The `key` action with text "a" — let's test and check the log shows ▼ C4 key:A and ▲ C4 key:A. Also `type` with "asdf" for multiple.

Also test auto-repeat: not directly possible (tool likely sends single keydown/keyup). I can at least confirm code path.

Also test blur release: can't easily blur the window... maybe clicking outside the iframe? Not available. I could verify by code review.

Let me do: click demo → screenshot (attempt to catch held chord).

The C4 key is highlighted (active state, teal) — press highlighting confirmed visually. Now screenshot immediately to catch the full chord (4 notes held until ~44s).

The second chord ran fully: 4 attacks, 4 releases, voices back to 0. The screenshot timing missed the held moment (screenshots appear to be taken ~1.5s after action). 

I want a visual of 4 simultaneous lit keys. Option: extend the demo hold to ~2.5s so a subsequent screenshot catches it. The screenshot after the click seems delayed by ~1.5-2s (the click's own screenshot caught C4 lit at 1 voice). Actually the click's screenshot caught the state right after the click (1 voice lit). Then a separate screenshot call ~2s later showed 0.

So: click demo → screenshot shows state at click time (1 voice). To catch 4 voices, I'd need a screenshot at ~+0.5s to +1.3s. The screenshot call itself has latency, so the previous screenshot came at +1.4s+ (after releases began at 44092).

Fix: increase the chord hold to ~3.5s so the follow-up screenshot catches all 4 lit. Let me change demo hold to 3000ms base. That's fine as a demo feature (it's my choice). Let me set release at 3200 + i*90.

Also, I want to verify keyboard events. Let me use the `key` action with text "a" and check the log.

Let me make the demo hold longer, reload, click demo, screenshot.

Now let me also review the input handlers for matching note-start/note-release behavior (the verification asks me to inspect them). Let me read the handler section of the file to double check correctness, then reload and test keyboard + demo.

Let me read lines ~400-500.

Handlers look correct. One issue: in `keydown`, `e.key.toLowerCase()` — for letters fine. Note: `if (e.repeat) return;` placed after preventDefault — fine.

Another: keyup after blur — downKeys cleared, so keyup no-ops. Good.

Potential issue: `noteOn` uses `held[note]` Set; if the same note is pressed by both keyboard and pointer, releasing one keeps highlight. Good.

`releaseAll` sets `held = {}` but the closure variable reassignment is fine (held declared with var in same scope).

One more: in keydown, if a modifier like Shift is pressed, `e.key` = "Shift" → byKey undefined → return. Good.

Also `Engine.releaseAll` in releaseAll() — releases all live voices. Good.

Also: `document.activeElement`/focus — keydown listener on window requires the iframe document to have focus. In the sandboxed iframe, keyboard events from the tool go to the page. Should work; let's test.

Now reload and test keyboard.

Now test keyboard. First, audio needs a user gesture; a keydown counts as a user gesture. Let's use `type` with text "asdf" (types A,S,D,F = C4,D4,E4,F4). Then check log.

Actually `key` action with text "a" first.

Keyboard works: key 'a' → C4 attack + release, key flashed (glow visible), audio unlocked via keyboard gesture, voices back to 0.

Now test a black key via keyboard, e.g. 'w' → C#4, and 'k' → C5. And test the demo chord visual with 4 held keys.

Let me do `key` 'w' then `key` 'k'. Then click demo and screenshot.

Actually let me batch: type "we" (C#4, D#4) to check black keys.

The `type` action produced no new log entries — so typing "weyk" didn't fire keydown events (maybe the type action requires focus in an input, or it dispatches char events to the focused element only, or the iframe lost focus). Let me try the `key` action for individual keys, e.g. text "w".

Maybe `type` sends insertText via CDP which doesn't produce keydown. So use `key`.

Let me test `key` with "w" (C#4).

Also, the page needs focus for key events; `key` worked earlier, so focus is fine.

Note: after the previous `key a`, the screenshot shows the C4 key still glowing (flash animation) — good.

Let me run key "w" and then key "k".

Black key W → C#4 works (attack/release logged).

Now test the pointer drag: press on a key and release outside the piano — verify the voice releases. Use `drag` from (168,400) to (600,700) (outside piano). Then check log: ▼ C4 pointer then ▲ C4 pointer, and voices 0.

Also test glissando: drag from C4 to E4 — log should show C4 on, C4 off, E4 on, E4 off.

Let's do the drag outside first.

Excellent: drag started on C4 (▼ at 27835ms) and released outside a key at 28053ms (▲) — voice released, count back to 0. Also the scope shows a waveform (the diagonal pattern is the analyser showing... hmm, that zigzag looks like a sawtooth-ish pattern — it's the waveform of the note decaying? It's actually a plausible waveform render). The scope shows activity — good.

Note the C4 key still shows the flash glow.

Now test glissando drag across keys: from C4 (168,400) to A4 white key (~782,400). Expect ▼C4 ▲C4 ▼E4?... intermediate keys.

Then test the demo chord with a screenshot to see 4 keys lit (hold now 3.2s; the screenshot after click seemed to be taken ~1.4s later? In the earlier test, the click's own screenshot showed 1 voice (taken immediately). Hmm, the screenshot attached to the click action showed the state right after pointerup (only C4 started). So the click's screenshot is immediate; a separate screenshot call has ~1.5-2s latency. With a 3.2s hold, a separate screenshot call should catch 4 lit keys.

Let me do: click demo → screenshot.

Actually careful: clicking demo button then screenshot: 2 calls. Let's try.

The click's DOM snapshot showed "Active voices: 1" (just C4 started), but the attached screenshot shows 0 voices — so the screenshot is taken ~1s+ after the DOM snapshot. Since the chord now holds 3.2s, let me take a screenshot right now (should be within the hold window, as the chord started at 38366ms and releases at ~41566ms; time now ~39.5s+).

Let me screenshot immediately.

The screenshot call happened at ~41.9s (after releases) — the tool's actions have ~1.5-3s latency, so screenshots land after the 3.2s hold ended (started 38.36, ended 41.83). Timing is tight. The log confirms 4 concurrent voices existed (4 attacks before any release), which proves polyphony ≥4 with Tone.Synth voices active simultaneously — the voice counter would have shown 4.

Let me try the `motion` action right after clicking demo — motion captures multiple frames over time, likely catching the held chord. Actually motion is a standalone action; it records frames while... nothing happens. Hmm.

Alternative: increase hold to 6s and click demo, then screenshot (latency ~2-3s → catches 4 lit keys). Let me set the demo hold to 6000ms and try once. If it works, I'll keep ~4000ms for a nicer feel (or keep 6s? A 6s chord is a bit long but fine; I'll use 5s).

Let me change to 5000ms and test.

Actually, polyphony is already evidenced by the log (4 overlapping attacks with no interleaved release) plus the "voice engine: Tone.Synth" path. A visual of 4 lit keys is nice-to-have confirmation of highlighting (already confirmed with 1 key). I'll do one attempt with a longer hold since it's cheap.

Also, I should double check the "Active voices" counter reaching 4 — the DOM snapshots at click time showed 1. Let me do the test: set hold 5000, reload, click demo, then inspect (fast) — inspect returns DOM text which includes voice count. The click's own snapshot is taken right after pointerup (1 voice). Then a second `inspect` call at ~+2s should show 4.

Let me do it.

Wait — reload resets the page; the click then a screenshot. But each tool call has ~1.5-3s latency, and reload+click+screenshot = 3 calls. The chord starts at click time; the screenshot arrives ~2-4s later → within 5s hold. Good.

Let me reload, click demo, screenshot.

Now click demo (first click also unlocks audio, so the first note might be skipped due to my "still held" check — no wait, the check is `srcNote[src] === note`, and demo notes are held for 5s, so after unlock they'll start. Good — actually the .then runs after unlock (~ms), still held → plays.

Click demo, then screenshot.

Two voices active simultaneously (C4 + E4) — polyphony confirmed. Let me grab one quick screenshot to catch 4 lit keys, then finalize.

Actually time is short. Let me do one screenshot call (it should land within the 5s hold) and then finish up.

4 simultaneous voices (C4, E4, G4, B4) all highlighted, waveform active. Everything verified.

Final tidy-ups (quick):
1. Shorten the demo hold back to ~1.6s (5s is long but harmless; I'll set 2200ms).
2. Remove the debug error/rejection handlers? Keep them — they're useful and harmless. Actually keep the unhandledrejection/error logging but it logs "[piano] error" — fine, useful diagnostics. I'll keep them.
3. The CSP worker error at load is from Tone itself (blocked blob worker) — unavoidable and doesn't affect sound.

Let me make the demo hold 2200ms and do a final quick syntax check + reload to confirm no console errors from my code.

Time is tight — do the edit, reload, and finish.

I need to reload and test a single key press to verify everything works and there are no new errors, then I'm done.

File is saved and clean. Done. Let me do a final syntax sanity check and report.

The file is saved. Final report.

Note: script tags = 2 (tone.min.js + inline). No external resources besides the local tone.min.js.

Report what was checked and what remains unverified.