> If you want the *fastest*, coolest 2D game physics for Ruby, be sure to
> look at Chipmunk:
>
>   http://wiki.slembcke.net/main/published/Chipmunk
>
> Just watch the sample videos on that site; it's amazing!

Mmm, the Sketch video is stunning. Now that is the sort of software I
would want my son to play with.

http://files.slembcke.net/chipmunk/movies/sketch.mov