Box2D physics engine for developing iPhone apps (reliable resource):
http://www.handcircus.com/2009/01/15/iphone-port-of-box2d-testbed-now-available/
or skip to checking out the code via svn:
https://box2d.svn.sourceforge.net/svnroot/box2d/
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how do i use box2d in my iphone apps? porting the box2d engine to iphone and ipod touch games. what do i need to do to use box2d in my iphone app? box2d to iphone/ipod touch port.