Rendering
three.js draws every object with instanced meshes, so hundreds of bodies cost about as much as one draw call per shape type. Soft shadows and a studio environment map do the rest.
One HTML file, a physics engine, no server.
Physics
Rapier, a Rust physics engine compiled to WebAssembly, steps the world at a fixed 60 Hz. The headline letters start asleep and wake up as their neighbours get knocked loose.
Hosting
It's all static files: HTML, CSS, JS and some WASM. Cloudflare Pages serves them from its edge network on the free plan. No build step, no backend.
Ship it in a minute.
npx wrangler pages deploy physics-site --project-name my-playgroundOr connect the repo in the Cloudflare dashboard and set the build output directory to physics-site.