Box2D for Unity
Box2D is the familiar physics engine used by many indie game developers. If you would like to use Box2D physics in pre-4.2 Unity, this package makes it as simple as drag and drop!
This package includes a DLL of the open source Box2D-Unity project, which we've ported to use Unity's built in types, and made available for free on github!
This package includes all the glue needed to get Box2D working with Unity. We've done our best to make it look and feel like the built-in physics so you can get up and running quickly!
Available on the Unity Asset Store.