Thanks! It was Cocos2D for graphics with Box2D for the physics engine. The hard part with Box2D (as with any physics engine, I assume) was tweaking the coarsene

Thanks! It was Cocos2D for graphics with Box2D for the physics engine. The hard part with Box2D (as with any physics engine, I assume) was tweaking the coarseness of the simulation to balance performance against visual quality.