Yep, I've always liked coding Verlet particle physics and mass-spring physics because they're easy to implement and fun to play with.
Here are a few other tests I made with my JavaScript Verlet engine (they were mainly made for Mozilla Firefox, I'm afraid):
http://projects.mezane.org/physics-e...html/test.html
http://projects.mezane.org/physics-e...ml/funnay.html (Use arrow keys)
I was thinking about how to turn Verlet physics + accelerometer into a game. One could make an obstacle course where the player has to rotate their phone to get through it.