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Rain on a Window (2D)

Interactive 2D rain-on-glass simulator: droplets form and grow, held round by surface tension until gravity along the tilted pane overcomes adhesion, then slide down and coalesce with everything in their path.

Everyday Physics2DEasy60 FPS📱 Mobile-adapted⇄ 3D version

This 2D companion to the 3D rain-window simulation looks straight at a pane of glass from indoors: raindrops land and grow into round beads held in place by surface tension and adhesion, until a droplet's weight along the tilted pane finally overcomes that pinning force and it slides, coalescing with every droplet in its path and leaving a streaked trail behind it. Raise the rain intensity to flood the glass faster, and tilt the pane toward vertical to watch smaller and smaller droplets break free and race down — the same contact-angle physics that decides whether a raindrop clings to your car window or streaks straight down it.

⚙ Under the hood

A 2D canvas view of raindrops forming on glass, held round by surface tension until gravity along the tilted pane overcomes adhesion and they slide down, coalescing with droplets in their path.

RainSurface TensionFluid DynamicsCoalescence

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install