Physion

Physion is a 2D physics simulator that runs entirely in the browser, with nothing to download or install. You draw rigid bodies directly on the canvas (circles, rectangles, capsules, polygons, regular polygons, gears, polylines, spirals and text bodies), connect them with revolute, weld, distance and wheel joints or with springs, and press play. It also simulates liquids, particle emitters and soft bodies, supports boolean shape operations (union, difference, intersection) and a laser raycast with script callbacks.

Any object can carry a JavaScript "node script", so a scene can measure itself, react to collisions, or drive its own motors. There is an assets library for images, fonts and scripts, and a public showcase of community scenes.

Its main use is education and STEM teaching, where the fact that students need no install and no admin rights on a school machine is the whole point, but it is equally usable as a sandbox toy.

Free to use, with optional paid plans.