Matrix digital rain · mimo-v2.6-flash

Let me build the index.html file with a Matrix digital rain effect.

Key features:
- Full-screen black canvas
- Columns of green katakana glyphs, independently moving
- Bright leading character, fading trail
- Vary column speed and start position
- Recycle columns after leaving bottom
- Pause/Resume and Restart buttons
- Resize handling without stretching
- No external resources

Let me write it.

Design:
- Each column: x position (in cells), speed (rows per second), y offset (head position in float), glyph set random per column maybe random per cell.
- Draw: instead of persistent canvas trails (which require clearing), I'll do full redraw each frame: clear to black, then for each column draw the trail: head bright white-green, trail segments with fading alpha. This makes pause freezing easy and restart clearing trivial.

Actually "fading trail" — full redraw each frame with alpha gradient based on distance behind head. That gives fading trail visually. Recycle: when head passes bottom + trail length, reset column to top with new random speed/x.

Let's do cell-based: fontSize = 16, cols = ceil(width/cellW). Column spacing with some gaps: each column assigned a random x cell index, possibly skip some cells for variation (multiple independently moving columns). Let's use fontSize 18, charWidth ~ fontSize * 0.6? For katakana monospace-ish, use measureText. Simpler: use monospace font, cellW = fontSize * 0.6... but katakana in monospace may be double-width in some fonts. Let's compute cell width by measuring "あ" or use a fixed. Actually we draw glyphs at fixed x positions, so overlap/spacing just needs to look fine. Use cellW = Math.round(fontSize * 1.0) maybe too wide. Let's measure with ctx.measureText on a sample katakana char and use max of that and '0' width... Katakana in many monospace fonts are full-width (2 cells). Let's just measure "ア" width and use that as cell width. If font renders it narrow, spacing is fine anyway.

Head brightness: brightest at head — fillStyle white-ish green (#d6ffd6 or rgba(190,255,190)) plus maybe shadow glow (shadowBlur). Others fade from green (0.9) to dark.

Trail length varies per column: e.g. 10-30 cells.

Speed: rows per second, vary 5-25. dt-based movement: headY += speed * dt (in cells).

Glyph: each drawn glyph should probably flicker/change occasionally — pick random glyph per cell per some interval; simplest: pick random glyph each frame for cells near head? That flickers a lot. Common approach: each column has array of glyphs regenerated randomly when drawing (or update a couple per frame). I'll assign each column a glyph array of length trail+something, and randomly mutate a few glyphs per frame (changes look alive). Or just pick glyph from hash of (colIndex, cellIndex, floor(time*changeRate)). Simpler: each column stores glyphs; on recycle regenerate; mutate random 1-2 glyphs per frame.

Pause: stop rAF updating, keep drawing? Just stop the loop (cancel or skip updates and skip redraw). Freeze = don't redraw. Resume continues with time delta reset (accumulate dt only when running).

Restart: re-init columns (new random x/speed), clear canvas (fill black).

Resize: on resize, set canvas width/height to innerWidth*dpr, style width/height 100%, recompute cols and rebuild columns layout (preserve? Spec says resize column layout to fit viewport). We rebuild columns — need to be careful: rebuilding on resize resets positions, that's acceptable. Avoid stretching: set canvas.width = w*dpr, ctx.setTransform(dpr,0,0,dpr,0,0).

No uncovered strip: canvas CSS width:100%, height:100%; body margin 0; overflow hidden.

Controls: buttons Pause/Resume (toggle text), Restart. Style with green border, black bg. Position top-right or top-left, fixed.

Also maybe a hint. Keep simple.

Let me write the code.

Glyph set: katakana half-width ｱ-ﾟ plus full-width ア-ン. Use a string: "ﾊﾐﾋｰｳｼﾅﾓﾆｻﾜﾂｵﾘｱﾎﾃﾏｹﾒｴｶｷﾑﾕﾗｾﾈｽﾀﾇﾍ" classic Matrix set plus アイウエオ... I'll build from codepoints: 0x30A1..0x30F3 (katakana) and 0xFF66..0xFF9D (halfwidth). Random selection.

Head detection: cells from headIndex going back. For column: headPos (float, in cells, y center = headPos * cellH + something). Draw cells i = 0..trailLen: cellY = headPos - i. If cellY in [-1, visibleRows+1], draw glyph with alpha = fading: alpha = i===0 ? 1 : pow(1 - i/trailLen, 1.6) * 0.85. Head color bright: rgba(200,255,210) with glow. Trail color green (0,255,70)-ish scaled by alpha.

Also slight color: use hsl(130, 100%, X%).

Glow: ctx.shadowColor/shadowBlur only for head to be performant.

Recycle: when headPos - trailLen > rows + 2 (all off-screen), reset: headPos = -random(0..trailLen?) Actually to vary start position, reset headPos = -(random * rows?) Hmm start above screen: headPos = -rand(0..rows*0.5)? Spec: "Vary column speed and start position. Recycle columns after they leave the bottom". Initial start: random negative positions so columns start staggered. On recycle, new random speed and trail length, headPos = -randomInt(0, someMax). Could also recycle to slightly different x? Keep x fixed per column for stability; maybe occasionally re-randomize x? If x changes, may collide/skip. Simpler: keep x but allow x jitter on recycle among free cells? Complexity — keep x fixed.

Hmm "independently moving columns" — varying speeds gives that.

Column layout: compute cols = floor(width / cellW). Create columns: for each cell index, include with probability ~0.75, else gap for visual variety. Number of columns could be many (e.g., 1200/16=75). Fine.

Also add a few slower/faster. Speed = 6 + rand*20 cells/sec.

dt cap: cap at 0.1s to avoid jumps.

Pause: `paused` flag; in loop, if paused, just don't update or draw — but rAF still runs. Better: on pause, record; on resume, reset lastTime. Or stop rAF entirely and restart on resume. I'll keep rAF running but skip update/draw when paused (simple), and set lastTime = now always so dt stays small.

Actually to be power-friendly: cancelAnimationFrame on pause, restart on resume with lastTime=performance.now(). Cleaner.

Restart while paused: re-init and keep paused? Reset then if paused, draw one frame so canvas shows fresh state (not old trails). I'll draw a frame after restart regardless.

Let me write.

Also visibilitychange pause? Not required.

Fonts: use local stack: '"MS Gothic", "Osaka-Mono", "Noto Sans CJK JP", monospace'.

Also random per-column font size variation? Keep uniform for grid alignment.

Write file now.

Draw loop:

```js
function draw() {
  ctx.fillStyle = '#000';
  ctx.fillRect(0,0,W,H);
  const now = performance.now();
  let dt = (now - lastTime)/1000; lastTime = now;
  dt = Math.min(dt, 0.1);
  for (const col of columns) { update & draw }
}
```

Update inside draw since redraw-every-frame.

Glyph mutation: col.glyphs array length = trailLen+1 maybe; mutate random 1-2 entries per frame: col.glyphs[idx] = randomGlyph(). On trail length change at recycle, regenerate array.

Actually simpler: glyph for cell drawn = col.glyphs[i % col.glyphs.length]. Fine.

Let me also add head "flash": a couple of cells near head brighter (alpha 1 for head, 0.75 for i=1, etc.).

Buttons: `<div id="ui">` with buttons. Also maybe a small label. Pointer events fine.

DPR: cap at 2 for perf.

Resize handler: debounce not needed; recompute layout (rebuild columns) — but "without stretching an old screenshot": since we redraw full each frame, after resize next frame redraws correctly. But if paused and resized, need a redraw after resize (frozen frame would be cleared). On resize: set canvas size (clears canvas to transparent/black), rebuild columns, and if paused, draw one static frame? Drawing a frame would advance nothing if we draw without updating. I'll make a `renderFrame(update)` function: if paused, render without updating dt (dt=0) so the image shows current state. Good.

Let's structure:

```js
function frame(){ ... update(dt); render(); raf = requestAnimationFrame(frame) }
```

Pause: cancel raf, render() once (dt=0). Resume: lastTime=perf.now(); raf=requestAnimationFrame(frame).

Restart: initColumns(); render() (clears since render fills black first).

render(dt): fill black, for each column compute advance (if dt>0), draw.

Wait, columns advance in render — mixing update/render is fine but let me separate: update(dt) then draw().

For paused static render: update(0); draw(). headPos unchanged, but glyphs mutate — mutation should only happen when dt>0. Put mutation in update.

Alright, code:

```js
const canvas = document.getElementById('rain');
const ctx = canvas.getContext('2d');
let W=0,H=0,dpr=1,cellW=16,cellH=20,rows=0,columns=[];
const GLYPHS = ...string
function randGlyph(){return GLYPHS[(Math.random()*GLYPHS.length)|0]}
function measure(){ ctx.font = fontStr; cellW = Math.ceil(ctx.measureText('ア').width) || 16; cellH = Math.ceil(fontSize*1.15)? }
```

Hmm cellH: fontSize*1.2 rounded. fontSize = 18 (desktop), maybe scale with viewport: fontSize = clamp(width/60, 14, 24)? Keep simple: fontSize = 18; if width < 600, 14.

Actually let's derive: fontSize = Math.max(14, Math.min(22, Math.round(W/64))). W in CSS px.

cellH = Math.round(fontSize * 1.25); measure "ア" for cellW, fallback fontSize.

Measure requires font set on ctx; set ctx.font before measureText.

drawText: ctx.fillText(g, x, y) where y = (i+0.8)*cellH baseline? For each cell index r (row), y baseline = r*cellH + fontSize (approx baseline) — use textBaseline='top' and y = r*cellH. Easier: ctx.textBaseline = 'top'; draw at (col.x*cellW, r*cellH). Then headPos in rows float; head row = Math.floor(headPos). Cell row r = headRow - i. y = r*cellH.

Column update: headPos += speed*dt. If headPos - trailLen > rows + 1 → recycle: headPos = -Math.floor(Math.random()*rows*0.6) - 1? Hmm start position varied: could start above screen or partially. Actually recycling to random negative offset means column appears after delay; but if offset too large, gap. rows*0.6 max offset gives staggered. Also new speed = 6+rand*18, new trail = 8+rand*22.

Hmm, but wait: if column resets to very negative, that region (top of screen) empty for a while — fine, other columns fill.

Initial: headPos = Math.random()*rows*1.5 - rows*0.5 → range [-0.5rows, rows], so some columns mid-screen initially. Good "vary start position".

Column x: iterate cells, include with prob 0.7 → gaps.

Guard: columns.length >= 1.

Pause button toggles: text "Pause" ↔ "Resume".

Let's also add glow on head: ctx.shadowBlur = 12; shadowColor = 'rgba(80,255,120,0.9)'. Set only when drawing head, reset after (shadowBlur=0). shadowBlur perf cost per column per frame — with ~60 columns ok.

Colors: head: '#eaffea' (near white). i>0: green with alpha: `rgba(0, ${g}, ${b}, alpha)` where base rgb(10,255,70). Use fillStyle with alpha computed.

Fading: alpha = Math.pow(1 - i/trailLen, 1.5); min 0.03. For i=0 alpha=1.

Brightness ramp: color lightness: mix from bright green to dark. Using alpha on black bg gives fading. Good.

Also the "brighter leading character" — draw head twice? Use fillStyle '#ccffdd' plus shadow glow. Also draw a slightly larger? Keep color-based.

Now resize: 

```js
function resize(){
  dpr = Math.min(window.devicePixelRatio||1, 2);
  W = window.innerWidth; H = window.innerHeight;
  canvas.width = Math.round(W*dpr); canvas.height=Math.round(H*dpr);
  canvas.style.width = W+'px'; canvas.style.height=H+'px';
  ctx.setTransform(dpr,0,0,dpr,0,0);
  layout(); // recompute rows & columns
  update(0); draw();
}
```

layout rebuilds columns (restart-like). Spec: "Resize the canvas and column layout to fit the viewport" — rebuilding columns is fine. But maybe preserve existing columns' positions when possible? Rebuild simpler. But careful: resize fires on mobile scroll... fine.

Actually to avoid resetting trails on every resize event (e.g., URL bar), I could keep column objects and just remap x if cols changed. Simpler: rebuild only if column count/x mapping changed; else just recompute rows and clamp headPos. Let's do: layout computes cellW/cellH/rows/cellCount. If columns.length is based on cellCount and cellCount changed → rebuild. Otherwise keep, clamp headPos (no clamp needed; off-screen columns just draw nothing).

Hmm, but glyph cells above old rows still fine since rows only affects recycle check (headPos - trailLen > rows+1). If rows shrinks, columns recycle faster — fine.

I'll rebuild columns only when cellCount differs (or columns empty). Also when fontSize changes (depends on W) cellH changes → fine, positions in rows units adapt automatically. 

Edge: cellW measure changes with font → cellCount changes → rebuild. OK.

Buttons HTML/CSS: fixed top center or top-right, semi-transparent black bg, green border, monospace.

Also add "click canvas to pause"? Not required, skip (could confuse verification). Keep buttons only.

Let me write the file.

Keyboard: space toggles pause, R restarts — nice extra but space might scroll; body overflow hidden anyway. Add it, harmless.

Write code now.

One more consideration for verification "independently moving columns": ensure visibly different speeds — speed range 4..24 rows/s. Also some columns could move downward only (all downward like Matrix). Yes.

Also maybe vary: some columns have longer trails. Yes random 8..30.

Draw order: fill black each frame → trails are drawn fresh each frame from head position → fading trail present. Good.

Restart clears previous trails: initColumns + draw → canvas filled black then new columns. Good.

Let me write.

Now run it in the browser and inspect.

Now load in browser and check console + screenshot.

No curl. Use browser tool to open index.html directly (file path or localhost). Let's try browser inspect on http://localhost:8777/index.html or file:///tmp/job-z0eQvp/index.html.

No curl/wget/ss. Try opening file:// URL directly in the browser tool.

Server may not be running (python3 may not exist?). Check python3.

No python. Use node to serve. Let's write a tiny node static server.

Server is up. Now use browser tool to open and inspect.

The browser tool likely opens a default index.html. Let me use the browser action reload/inspect — but how do I give it a URL? The browser tool description says "Run index.html, inspect DOM/console". Probably it runs the file in cwd. Let's just call inspect.

The rain is rendering: columns of green katakana with brighter leading chars and fading trails. No console errors. Now sample at several moments to check movement/independence, then pause/resume/restart checks.

Take screenshot now, wait, take another, compare motion. Also crop-check brighter heads: visually heads appear white-ish.

Let's take a screenshot now (second sample).

Wait, I should use browser screenshot action to capture a new frame.

The animation is clearly running: columns moved between frames, different columns at different positions/speeds, brighter white-ish heads visible, fading trails behind them.

Observations:
- Columns move independently — yes, different trails at different positions.
- Brighter leading character — visible white heads.
- Fading trail — visible, fades to dark.

One thing: the second frame shows fewer bright heads? Actually there are white heads visible (e.g., "9", "0", "口", etc.). Fine.

Now test Pause: click the PAUSE button, then screenshot twice to confirm frozen (identical frames). Then Resume and confirm continued motion. Then Restart and check old trails cleared (image differs entirely / trails gone).

Click PAUSE at (1049, 29).

Button now says RESUME → paused. Now wait and take another screenshot to verify the image is frozen (identical).

Now screenshot to compare with the paused frame.

The paused frame is pixel-identical to the previous one (glyphs at same positions). Pause works.

Now Resume (click RESUME at ~1047,28), wait, screenshot, and confirm it moved again.

Resumed (button back to PAUSE) and the frame has advanced from the frozen state (glyphs changed, e.g. heads moved down slightly — head "9" at y=310 became "ケ"... actually looking, leftmost column head ム at 308 unchanged but that column may be slow; other columns show change: "9 美" changed to "D 9 美"... anyway glyphs differ from frozen frame). Motion continues.

Now let's wait a moment and screenshot again to confirm continued motion more clearly, then test Restart.

Let's screenshot to confirm continued motion, then click Restart. Actually to save budget, I'll screenshot now (motion check) and then click restart.

Motion continued after resume — completely different positions. Columns at different positions moving at different speeds (heads at varying y: y=110, 257, 435, 464, 506, 659, etc.) confirming independent movement.

Now test Restart: click RESTART at (1142, 28). Then immediately screenshot to check that old trails are cleared (fresh columns from staggered positions; since initial heads random, some region should show trails freshly drawn but old long trails gone). Since restart rebuilds with random initial positions, the image will look entirely new. To check "old trails cleared", the key is the canvas is repainted black first — the frame should not contain the previous frame's content.

To be rigorous: pause first, screenshot frozen frame, then restart while paused, screenshot → if old trails cleared, the frozen content is fully replaced by a fresh (also frozen) render. Actually restart while paused draws a static fresh frame; then resuming continues. That's a good deterministic check: the image after restart must differ entirely from the frozen paused image (no leftover glyphs from the paused frame).

Let's do: click RESTART while running, screenshot immediately → different content. Then also test restart while paused.

Plan:
1. Click RESTART (running). Screenshot → new fresh image, content differs from previous entirely.

Note: immediately after restart, the columns are at random initial positions — some already on screen, so trails appear full. That's fine.

Better check for "old trails cleared": pause first so frame is frozen, click restart → the frozen glyphs should be gone (replaced by new ones). Let's do that sequence: pause, screenshot (have it), restart, screenshot compare.

We already have a frozen image from earlier paused state. Simpler: click PAUSE now, screenshot, then click RESTART, screenshot → compare: entirely different glyphs means repaint happened (old trails cleared).

Let's do it.

Now frozen (RESUME shown). Now click RESTART and screenshot — the frozen content should be completely replaced (old trails cleared).

Restart while paused produced an entirely fresh frame — completely different glyphs/positions from the frozen frame, so old trails are cleared. Also still paused (RESUME shown), meaning restart preserves pause state and renders a fresh static frame.

Now resume and confirm animation continues after restart. Then test resize (change viewport) — the browser tool uses fixed 1200×800 viewport; can I resize? The browser tool has no resize action. Hmm. Resize verification: I could dispatch a window resize event via... the browser tool doesn't have eval. Actions: reload, inspect, screenshot, motion, click, drag, key, type, scroll. No eval/JS execution.

Alternative: verify resize handling by reasoning + maybe use a smaller viewport? Not possible. I can at least confirm code correctness by reviewing. Another way: the "drag" action might resize? No.

I could check uncovered strip by reasoning: canvas fixed at top-left with width/height 100% of innerWidth/innerHeight, resize handler debounced 60ms repainting.

Hmm — could I verify resize via keyboard? No. But maybe scrolling causes mobile-like resize — not here.

Alternative approach: temporarily add a query param test? Not needed.

I can at least simulate the resize logic in node: extract the script? Hard without DOM/canvas.

Let me do a lightweight logic sanity test in Node: run the update/reset math to check recycling doesn't accumulate off-screen state (columns count constant, heads stay bounded). I can stub minimal functions. Actually simpler: review code mentally — resetColumn sets head negative when recycled; columns array length fixed after build. No accumulation. Good.

Let me test resize by reloading the page at a different viewport? The browser tool viewport is fixed at 1200×800 per docs.

Option: use the `drag` action to drag the window edge? No, drag is within page coordinates.

I'll consider resize unverified by direct interaction, but I can do a partial check: reload and confirm canvas covers full viewport with no uncovered strip (already visible: full black coverage with rain to edges — from screenshots, glyphs reach the right edge x=1190 and bottom).

Actually, I could verify resize indirectly: window.resize handler calls resize() which uses window.innerWidth/innerHeight. I can test that logic in Node by extracting the script and stubbing document/window/canvas/ctx. That's a decent functional test: simulate innerWidth change, call resize, assert canvas.width updated and no uncovered strip (canvas.width/dpr === innerWidth), columns rebuilt. Let's do that — it's a reasonable automated check given no viewport resizing in browser tool.

Let me write a stub harness. The IIFE runs on load: resize(); start(); — requestAnimationFrame stub needed to avoid infinite loop (collect callback, don't auto-run, or run limited frames).

Stub plan:
- document.getElementById → fake elements with addEventListener, textContent.
- canvas: {width,height,style:{}, getContext: ()=>ctxStub}
- ctxStub: measureText: (s)=>({width: s==='ア'? 18*1.0 : 9}) ... Actually katakana full-width ~ fontSize. Return {width: 20}.
- ctx methods: font setter, fillRect, fillText, measureText, setTransform, etc. Track fillRect count and fillStyle for black clears.
- window: innerWidth/innerHeight mutable, addEventListener, devicePixelRatio, requestAnimationFrame/cancelAnimationFrame, performance.now, setTimeout/clearTimeout (real), document.hidden, document.addEventListener.

The script references: window.devicePixelRatio, window.innerWidth/innerHeight, window.addEventListener, requestAnimationFrame (global), cancelAnimationFrame, performance, setTimeout/clearTimeout, document.addEventListener, document.getElementById, Math.

Then after load: assert canvas.width === innerWidth*dpr, columns count>0; change innerWidth to 800, fire resize listener (need to capture handler; debounce uses setTimeout 60 → use real timers with await), then assert canvas.style.width === '800px' etc.

Also I can run frames manually: raf stub stores callback; call it with increasing timestamps to advance and check columns recycle: run e.g. 60s of simulated time, assert all heads within bounds relative to rows (i.e., head - trail <= rows+1 or head negative) → no accumulating off-screen state, and columns length constant.

This gives good verification of update/recycle logic. Let's do it.

Then in browser: resume after restart, screenshot to confirm animation continues. Also check console already empty.

Let's do browser resume first, then node harness.

Let me click RESUME (at ~1047,28) and screenshot after a moment.

Resumed: animation advanced from the post-restart frame (glyphs shifted, new heads). Button back to PAUSE.

Now let's do the Node harness test for recycling logic and resize handling, since the browser tool can't change viewport size. Also I want to verify column recycling doesn't accumulate off-screen state and columns move independently (different speeds).

Harness: extract the inline script content from index.html, run in Node with stubs.

All checks pass:
- Canvas covers viewport exactly at DPR scaling (no uncovered strip, no stale scaling).
- 5401 frames over 90 simulated seconds: one black clear per frame, fillText bounded (~413/frame avg = 2.2M/5401 ≈ 413) → no accumulation of off-screen state; head draws bounded per sample (head counts at 10s samples: 58 at first frame then stable ~14162 per 10s... wait those are cumulative headDraws since headDraws never resets. Difference between samples ≈ 14162 constant → consistent head-per-frame count, meaning column count constant → no runaway columns).

Let me verify: fillTextsTotal/frames = 2231061/5401 ≈ 413 glyphs per frame — bounded. headDraws increments: first sample 58 (partial), then increments of ~14162 per 600 frames = ~23.6 heads/frame → ~24 columns with head visible on screen... plausible.

Also check recycle: does head position ever get stuck off-screen? The bounded glyphs/frame confirms recycling works (otherwise columns would leave screen and glyph draws would drop to 0). Actually over 90s, average glyphs/frame stayed constant at ~413, meaning columns recycle and keep rendering. 

Also verify independently varying speeds: by construction speed = 4 + rand*20 per column, reset on recycle. Observed visually in screenshots (heads at different y, columns at different progression).

Now, pause/resume/restart via buttons in harness all pass; in browser pass too.

Remaining: check the browser console was empty — yes, "console":[] all frames.

One more: keyboard shortcuts — quick browser test via key action? Space toggles. Could test quickly: press key... The browser `key` action takes text? Let's do a quick check: press space → button should become RESUME. Then press again. And 'r' restart. Let's do it briefly.

Also check reduced uncovered strip visually: screenshot shows glyphs across full width including right edge — yes.

Let's test keyboard quickly.

Space paused (RESUME). Now press Space again to resume, then R to restart — quick check both work. Let's do space first.

Let's press space again to resume, then r to restart. Combine? The key action sends one key. Do space first.

Resumed (PAUSE shown, frame advanced). Now press R to restart.

Press r key.

R restarted: entirely new glyph layout (dense fresh initial state, old trails gone), still running (PAUSE button). Console empty.

Everything verified. Final file is saved. Let me kill the temp server (optional, tidy) and confirm index.html exists.

Note: the harness eval'd the script from the file — didn't modify the file. The file is final as written.

Quick final check: file exists and content intact.

Done. Report what I checked and what remains unverified.