Matrix digital rain · particle-1

I noticed a problem: I clear the full black background each frame (fillRect with alpha 1), which means no trail smear, but I draw fading trail explicitly as alpha per glyph. That's fine. However, the trail drawing is off: the "fade" for characters. Also head glyph at t=0 continuous bright. Good.

But wait: columns drawn with trail behind head downward? In Matrix, trail extends upward from the head (head at bottom of the trail). I draw rows headRow - t, i.e., above the head. Correct.

Issue: paint order — trails drawn with per-column alpha, fine.

Also there's a bug: in drawScene, `col.glyphTimer += dt` even when dt===0 on resize; harmless.

Another potential bug: restart() uses colWidth computed in computeMetrics; fine.

Let's run the browser.

Looks decent, but heads seem bright at some spots. Trails are quite dim/faint but fine. Let me sample later frames and check motion, then pause/resume.

One observation: head brightness looks okay but some columns' heads are hard to spot. Let me check motion frames and console.

Motion is working, columns independently moving, bright heads and fading trails. The trails are somewhat faint — mid part of trail is dark. Acceptable but could bump brightness a bit. Let me strengthen trail visibility slightly, and check pause.

Also note column head positions move downward over frames; some columns reset. Good.

Let me verify pause by clicking, then screenshots at two times, compare. I'll do programmatically via browser click and screenshots.

Button now says RESUME. Now wait a bit and screenshot to confirm freeze.

Frozen — identical frame (pause works). Now resume and check motion, then restart clears old trails. Also I want to slightly increase trail brightness. I'll tweak: alpha exponent 1.7 → maybe keep but raise base multiplier; also the head glow is strong which is good. The trails mid-section are quite dark; user asked for fading trails — present. I'll bump a bit: alpha = pow(fade, 1.45)*0.95.

Also issue: the trails look like they end abruptly because trail length limit; acceptable.

Let me make the trail a bit brighter and then verify restart.

Resumed, same layout continued moving (columns advanced). Note the last frame before reload was under old file? Actually the file was edited but not reloaded; the browser shows the old version still running — fine, both similar.

Now reload to test new version, then restart to check trails cleared, and resize behavior. Let me reload and immediately click Restart.

The new version looks brighter trails. Now click Restart and screenshot to check clearing.

Restart cleared prior trail state and started fresh: columns now short/new trails emerging from varied positions. Old trails gone.

Now check resize (canvas fit, no uncovered strip). Resize viewport — browser tool has fixed 1200x800 viewport; I can use JS to check via DOM? I could check window resize by executing... The browser tool doesn't allow arbitrary JS eval. I can simulate via CSS? Alternatively, I can resize in an iframe test file... Simpler: write a small test page that iframes index.html at various sizes? Same-origin file iframes might work, checking canvas size matches iframe. Let me create test.html with multiple iframes of different sizes and screenshot. Since it's a sandboxed env loading via http, likely same origin. I'll do it.

Also test toggling paused state via keyboard maybe skip.

Let's create test.html with iframes 420x700, 1000x300, and check each has black coverage and layout fits by screenshot. Note devicePixelRatio and visualViewport inside iframe should match iframe size.

The browser reload loaded index.html (not test.html). I can't navigate to test.html via the browser tool directly? Maybe reload just reloads current URL root. I could temporarily rename: copy index.html aside, replace index.html with test page? That would break final state but I can restore. Simpler: use bash with a headless check? No playwright likely. Let me check if node/puppeteer available... probably not. Alternative approach: make index.html itself test resize by checking canvas pixel dimensions via a debug overlay? I can add a temporary test route inside the page? The browser tool only loads index.html, so I can temporarily add a script that resizes the window? Can't resize browser.

Another approach: temporarily change the page to include a hidden iframe test harness that runs at load, programmatically resizing iframes and logging canvas coverage to DOM (which I can inspect). Iframes to index.html from index.html would recurse. Better: create a copy matrix.html, then temporarily make index.html a harness that loads matrix.html in iframes of various sizes, measures canvas width/height and pixel coverage, writes results into DOM, then restore original index.html when done. Since I need final index.html intact, I'll do: cp index.html matrix.html; write harness to index.html; verify; then restore cp matrix.html index.html.

Let's do that with a harness that programmatically changes iframe sizes sequentially (resize scenario) and reads canvas.width/height and pixel stats. Same-origin check needed. Also check that after resizing from large to small, no uncovered strip: sample pixels along edges through canvas getImageData inside iframe. Let's write it.

CSP blocks iframes. Alternative: test resize behavior within a single page by temporarily embedding the app in an iframe via srcdoc? CSP default-src 'none' likely also blocks srcdoc child contexts? srcdoc might be allowed as it's inline; but script inside iframe srcdoc would inherit CSP maybe allowing inline scripts? Uncertain.

Better alternative: use bash + headless browser? Check for node modules like puppeteer/playwright and chromium binary.

Playwright available in /app/pipeline/node_modules! Check browsers installed.

Resize works: canvas matches viewport exactly each time, no overflow, brightness up to ~246. Pause screenshot compare gave false — but screenshot compare across calls might differ due to restart animation? Wait pausedSame=false means screenshots taken while paused differ. Hmm, maybe screenshot captured mid-frame timing (the frame buffer changes between screenshots due to compositor timing?). Since paused, no draw calls occur, so pixel content shouldn't change... unless the screenshot comparison includes the button hover/focus animation (CSS transition on background/box-shadow) at the moment of click! Yes — screenshot `a` taken immediately after click while CSS transition running; `b` 1.2s later after transition completes. That explains difference. Need to verify pixel freeze using canvas getImageData hash instead. Let me do a quick dedicated test: capture data URL of canvas before/after pause, and also confirm frameCount stops increasing.

Also litRatio ~0.05 means only 5% grid cells lit; that's low-ish but rain is sparse; screenshot looked good. Could increase density? Visually fine.

Let me run the pause pixel-hash test.

Pause truly freezes pixels and frameCount, resume advances, restart changes content. Everything verified.

One more thing: sizing responsiveness with dpr > 1 wasn't tested (deviceScaleFactor). Could run with deviceScaleFactor 2 quickly. Also test restart clears previous trails specifically — screenshot showed new short trails. Fine.

Let me run a quick dpr=2 check for edge coverage (canvas size = css*2, no uncovered).

All good at dpr=2. Now final cleanup: index.html is the final matrix app (already restored), remove matrix.html/test.html. Ensure index.html intact.

Then brief report.