This experiment was done in 2009 using Box2DJS[1] for the site Chrome Experiments[2]. Since then I've been improving it by cleaning up the code, adding DevideOrientation support and, some weeks ago, updated it to the new google.com design.
Fun fact: The API being used has been deprecated for a while and, as far as I know, there is no alternative.
[1] http://box2d-js.sourceforge.net/ [2] http://www.chromeexperiments.com/