Box2D

Box2D is a free open source 2D physics simulator engine written in C++ by Erin Catto and published under the MIT license. It has been used as the engine of several Angry Birds games.

Angry Birds games that use Box2D

 * Angry Birds (Lite/Lite Beta/Free/Free with Magic)
 * Angry Birds Seasons (Free)
 * Angry Birds Rio (Free)
 * Angry Birds Space (Free)
 * Angry Birds Star Wars (Free)
 * Angry Birds Star Wars II