[patricklynch]

Right Click ==> View Source, obviously :D http://www.google.com/events/io/2011/static/js/io.js

So, it looks to be built on the Box2DJS Javascript physics engine: http://box2d-js.sourceforge.net/

The author, Matt King, says he recently got into Javascript through Crockford's "JavaScript: The Good Parts," and seems to be knocking it out of the park: http://mking.me/