Particles & Physics

Bouncing Balls

7–14 glossy pastel balls bounce off walls and collide with elastic physics; cursor repels balls within a 70px radius.

canvasmedium complexitymoderate motionpointer

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Live demo — the real component, running in a sandbox. One self-contained HTML file, zero dependencies. Open it on the canvas →

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When to use it

Ambient physics backgrounds, playful landing pages, or demos showcasing interactive particle systems.

When not to

Content-heavy layouts where constant motion distracts from reading; low-end devices sensitive to per-frame O(n²) collision checks.

Working with an AI agent

Every component ships agent-ready metadata. An example instruction for this one:

Change the palette to warm sunset tones by replacing the pal array with ['#fb923c','#f472b6','#facc15','#f87171','#e879f9','#fbbf24'], and increase max ball count from 14 to 20 in the init() function. Theme: dark tokens live in :root, the light variant in :root[data-theme="light"]; ?theme=light or a {type:'forever:theme'} postMessage switches at runtime.

Safe to edit

ball count range (7–14, from W*H/9000 formula)
color palette (pal array)
cursor repel radius (70) and strength (0.6)
max speed cap (5)
ball radius range (7 + random * 18)
theme tokens (:root dark defaults + [data-theme=light] overrides)

Keep intact

DPR-aware canvas sizing and setTransform
visibilitychange pause/play guard
elastic collision momentum transfer math (p=2*(dvx*nx+dvy*ny)/(a.m+c.m))
theme hook (?theme= bootstrap + forever:theme message listener + theme tokens)

Known limitations

O(n²) collision detection — scales poorly beyond ~20 balls
No reduced-motion fallback beyond skipping the animation loop (draws one static frame)
Background color hardcoded in CSS (#0a1418)

physicsballscanvascollisionelasticparticlesbouncing

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