Verlet–js is a framework shared by Sean at subprotocol.com earlier this week. If you’ve worked with physics engines before, you’ve probably heard of Verlet integration which is often used for the math behind putting particles in motion. This is a JavaScript implementation of it, complete with some very fun examples. Cloth and spider web are pretty much guaranteed to make you smile.
The source for verlet–js is on github so you can easily dig right into the code or just snag it to use in your own experiments. There’s a short guide to getting started with it too.