Utilizing the popular open-source Bullet Physics engine, recoil simplifies the setup and execution of complex physical simulations by combining robust collision detection with a variety of constraints, forces, and controls. By simply tagging any mesh item to be dynamic, it is ready to respond to forces like gravity or collisions from other objects in your modo scene. The recoil plug-in lets you quickly create incredibly complex animations of interacting objects that would be almost impossible to simulate manually. It is also useful for -stacking- up objects so that they rest against each other (see gumball image below).