Matter.js – A 2D rigid body physics engine for the web
Pros: The samples play well, look fun, and it looks like a great solution to small physics demos in JS. Great job!Cons: Playing with the Stress demos (especially #2) really shows the slowdowns and downsides to using a JS based engine. At 450 boxes (+ 4 bounding walls), it runs at 20fps  on my Macbook and thats with a lot of jitter and overlap. Not as fun.Edit: Significantly better w/ WebGL render, @32fps, and with sleeping+WebGL render @34fps.I wish I could see a physics engine using WebGL and GPU acceleration for the web. This one is a great start if the author were to take it further and implement some of the logic with shaders.