Flow-field particles · deepseek-v4.1-flash

Let me build the flow field particle animation. Let me first check the directory.

Let me write the index.html. Design:

- Full screen canvas via p5.
- 2500 particles with position, velocity, color hue.
- Perlin noise field: angle = noise(x*scale, y*scale, z) * TWO_PI * 4? Use field scale. Also evolve z over time.
- Trails: draw translucent black rect each frame instead of clearing. But trails need fading. Use low alpha background rect each frame. That's fine, not allocating growing history.
- Particle colors vary over time: hue based on position + time.
- Recycle particles when out of bounds: respawn at random edge.
- Pause/Resume and Restart buttons as HTML overlay.
- Responsive at 1200x800.

For performance with 2500 particles, drawing each as small ellipse with p5 at 60fps might be heavy. Better use point or small rect. p5 stroke + point. Actually we could use standard canvas 2D context via p5's drawingContext for speed. But using p5 functions is fine-ish. 2500 points per frame is okay.

Actually, to leave trails with fading, every frame fill background with rgba(0,0,0,0.06) and then draw particles. The accumulated alpha creates trails. Good.

Use p5 in global mode with setup/draw.

Need field to evolve gradually: z = frameCount * 0.002.

Particle color: use HSB? Set colorMode(HSB). hue = (noise offset + time) etc. Each particle has a base hue that shifts slowly.

Let me implement with drawingContext for performance using canvas API directly? p5 global is required. We can still use p5 for setup canvas and use ctx internally. But mixing is fine. Let's just use p5 drawing functions but use `strokeWeight` and `point`. p5 point() is fine.

Actually for 2500, computing noise each frame = 2500 noise calls, fine.

Let me use typed arrays for performance? Simpler: array of objects.

Movement: vx = cos(angle)*speed, vy=sin(angle)*speed. Smooth direction by lerping particle's heading toward field angle to keep local coherence. Actually nearby particles following local field already coherent. Add slight momentum for smoothness.

Bounds: when x<-10 or x>w+10 etc, recycle to opposite side or random position. "Recycle particles at the canvas boundaries" - respawn from random edge.

Restart: clear particles array reinit, clear trails by drawing background fully opaque once.

Controls: fixed top-left buttons. Responsive.

Let me also handle resize.

Pause: noLoop/loop, button text.

Let me write it.

Field scale: noiseScale = 0.0025. angle = noise(x*ns, y*ns, z)*TWO_PI*2.

Speed ~ 1.5-3.

Let me write the file.

For trails color: each particle leaves colored stroke; fade to black. Colors vary over time via hue = (baseHue + t*10 + noise*40) % 360. Use colorMode HSB with alpha maybe. To make trails colorful, stroke with full brightness.

draw: ctx background fade. I'll use p5: noStroke(); fill(0, 0, 12... ) hmm with HSB. Easier: use drawingContext.fillStyle = 'rgba(4,6,14,0.05)'; fillRect. But then p5 colorMode irrelevant for background. Use ctx directly for fade; then p5 stroke for particles. p5 will use its own stroke settings. Mixing fine.

Let's use drawingContext for both for speed: ctx.strokeStyle = `hsla(...)`; ctx.beginPath moveTo/lineTo. Actually drawing lines short segments gives motion blur but trails come from fade. Point is simpler.

I'll use ctx directly: for each particle draw a 1.5px rect or arc. Line from prev to new gives smoother. But prev not stored. Just fillRect(x,y,1.6,1.6). 2500 fillRects fast.

Color string construction 2500/frame creates garbage but acceptable. Could precompute palette of 360 colors and index. Better: precompute array of hue strings at 1-degree increments with fixed alpha. Then choose index. That avoids string alloc. But colors varying over time fine via index.

Actually to vary brightness/alpha maybe. Keep simple: precompute 360 hsla strings.

Let me do that.

Trail fade: rgba(3,5,12,0.06). At 60fps, trail decays to ~ e^-3.6 per second. Fine.

Restart full clear: ctx.fillStyle='#03050c'; fillRect.

Let me set initial particles spread across screen.

Let me write.

Also pause should stop animation but keep trails. noLoop.

Buttons: HTML div with buttons, stopPropagation.

Let me code.

One issue: window.setup defined inside IIFE but p5 global mode reads window.setup at load time. Since script runs and p5.min.js loaded before, p5 global mode will call window.setup after DOM ready. Actually p5 checks for global setup/draw. Defining them on window works.

But there's a subtlety: `restart()` calls redraw() when paused. p5 redraw() only works if the draw function is registered. Fine.

Also `frameCount` while paused stays same; redraw works.

Let me run browser.

Frame 1 already looks good. Let me check motion after some time.

Motion clear, field evolves, trails. Now test pause/resume and restart. Pause button at ~(43,29). Click. Then screenshots to verify frozen. Then restart.

Paused. Now screenshot twice to confirm it's frozen.

All 4 identical = paused correctly. Now resume and restart. Click Resume, then Restart.

Resume worked (button says Pause, trails moving), Restart cleared trails completely and shows new full-screen arrangement. Everything works. No console errors. 

Let me quickly verify no console errors via inspect.

All good. Final report.