Matrix digital rain · qwen3.8-max-0902

Let me try building it.

Design: Full-screen canvas, columns sized by fontSize, each with y position, velocity, and character set. Animation via rAF using frame skipping based on per-column timing.

Implementation: Each column has y (in cell units), velocity (cells per second), and accumulates time. Every frame, update the position. Drawing: fade the entire canvas with a black rgba every frame (trails), and draw a bright leading glyph and green trailing glyphs.

A better approach for clean fades: Use a trail buffer with per-column history, drawing glyphs with decreasing alpha every frame. This avoids the smearing that comes with global fade (which can leave residue). But the canvas fade approach is classic. Problem: fading leaves a faint residue, and restart requires clearing. Let's do explicit rendering: every frame, clearRect and draw the last N cells of each column with computed alpha. This makes pause/resume and restart clean, with no accumulated state. Cost is not a problem.

Character glyphs: katakana unicode 0x30A0-0x30FF, plus a few Latin letters and numbers.

Draw bright leading character: white/light green, and also occasionally swap out trailing characters.

Pause: cancel rAF, but keep the last frame as is (since we redraw completely every frame, we just need to stop rAF; the canvas retains its contents). Restart: reinitialize columns, clear the canvas, and if paused, draw one frame.

Resize: set canvas width/height to innerWidth/innerHeight * devicePixelRatio, rebuild columns to cover the width, and clear.

Buttons: a fixed overlay at the top, maybe hidden. Also, keyboard space to pause, R to restart.

Let's write it.

Note: restart while paused — buildColumns uses rows, and elapsed gets reset. No problem. But should restart also unpause? It's not required, so keep the paused state while displaying the new frame — acceptable. draw() renders the new columns.

Let's test in the browser.

At the first frame, only a few columns are visible near the top (the initial staggered placement). This is as expected at t=0. Wait a bit and take a screenshot. Use the motion action or a screenshot after a delay. The browser tool's "motion" captures frames over time. Let's use motion to sample multiple moments.

The animation is working: columns move independently at different speeds, bright leading glyphs (white with glow), fading green trails. Looks good.

Next, test pause: click Pause, take 2 screenshots at intervals, and confirm the image is frozen. Then resume, and confirm motion. Then restart, and confirm that old trails are cleared.

Paused. Next, take screenshots at two points in time to confirm that the frames are identical (frozen). After that, resume and confirm motion.

The paused frames are identical (same glyph positions as the previous screenshot). Confirmed the freeze. Next, click Resume and verify that the motion continues.

Resumed — comparing with the paused frame: positions have shifted slightly (e.g., the leading glyph of the column at x≈40 moved from y≈370 to y≈320? Actually the leading "T+" is at 421, and previously it was 421... hmm, comparing: in the paused screenshot the leading "T +" was at (240,421); now "T +" is at (240,421)? Wait, this screenshot was taken right after the click, so very little time has elapsed. Some glyphs have changed (e.g., "=3" → "=$", "C Q" moved). Actually, the leading glyph of the column at x≈563: previously "C Q" was at (563, 347/369); now "サ 2 / C Q" is at (583,331/347/369)? Slightly different. Motion has resumed. Let's take another screenshot after a delay to confirm clear movement, then click Restart to verify the clearing.

The columns have clearly moved (positions are completely different from before) — the animation is continuing after resume. Next, click Restart and confirm that the old trails are cleared: after restart, the columns should be reset to staggered start positions (above the top edge of the screen), so the screen should display only the new columns near the top, with no old trails remaining.

Restart cleared everything — the canvas is pitch black, with only a single leading glyph entering from the top-right (the staggered start positions are all above the screen). This confirms that the old trails have been cleared. But at t=0 after restart the screen is almost empty; the columns appear with time offsets. This is by design (staggered start), but it might look better to have some columns already on-screen at restart time. The initial build (on load) also uses `initial: true` and starts from -random*(rows+TRAIL), all above the screen. Hmm, at load time the first motion frame showed several columns on-screen at +576ms... Actually, the first screenshot after reload showed columns at the top. With speeds of 6–28 cells/sec, after 1 second the columns have advanced 6–28 cells. The staggered range of -(rows+TRAIL) means some enter quickly.

For a better experience, at restart/init I could distribute some columns within the screen: startY = random from -TRAIL_LEN to rows. Let me improve: initial start: Math.random() * (rows + TRAIL_LEN) - TRAIL_LEN → some on-screen, some above. This gives immediate coverage. The first motion frame at +576ms showed enough columns, so it's fine, but at restart the screen goes almost completely black for about 1 second. The requirement is "Restart resets columns and clears previous trails" — satisfied. But visually, having some columns on-screen immediately after restart would be better. Let me adjust makeColumn's initial to distribute across the full height: startY = -TRAIL_LEN + Math.random() * (rows + TRAIL_LEN). For recycling (non-initial), keep it above the top.

Wait: if the head starts in the middle of the screen, the trail slots above the head get drawn immediately (the trail is drawn behind the head), so it looks like a complete column suddenly appears — acceptable and typical.

Also check resize behavior. Let me test resizing the viewport... The browser tool's viewport is fixed at 1200x800; can I test resize via evaluate? There's no evaluate action. Can I test with scroll? Not applicable. I'll trust the resize handler logic: rebuild columns, clear, redraw. Can I simulate by dragging? Not possible. Skip; the logic is simple.

One more check: pause freeze was verified by two identical screenshots. Resume verified. Restart verified (cleared to black, new columns entering).

Let me apply the initial distribution adjustment, reload, and verify that the initial frame shows columns on-screen.

Reload and check the initial frame and restart. Also, I want to quickly verify the resize behavior, but I can't easily resize the viewport with the tools. However, I can at least confirm that the handler exists. Maybe I can test resize by using browser key/scroll? Not possible. I'll trust the logic.

Reload, take a screenshot, click restart, and take a screenshot.

Full coverage at load time: columns are distributed across the entire screen, with bright heads and fading trails, and varying speeds/positions.

Next, verify whether restart immediately displays distributed columns: click RESTART and take a screenshot.

On restart, a completely new set of columns (different glyphs/positions from before the restart) is immediately displayed across the entire screen, and the old trails are cleared. All required behaviors have been verified:

- Independent columns with varying speeds/starting positions ✓
- Bright leading glyph + fading trail ✓
- Pause freezes (identical frames), resume continues ✓
- Restart clears trails and resets ✓
- Resize: handler rebuilds columns and clears; logic verified by reading (couldn't resize the viewport in the tool, but the code resets the transform, rebuilds, and redraws).
- No external resources ✓
- No console errors ✓

Done. Reporting.