   2D Collision Detection for Physics Demo
  I'm developing a 2D Physics Engine [c++] (simple, lately I've been doing huge and unrealistic projects, so this one I'll finish since it won't be too complex).  I've got drawing, input, and everything I need (I've taken physics classes and know how to implement it), but what I don't have is a way to detect collisions.I've searched and seen a lot of posts about the SAT method and the Polycolly demo, and I'm definately going to try them out, as they look promising.  But they only deal with convex polygons.  Some polygons that I would like to use will be concave(like maybe an L shaped box).  Is there a simple way to do this, either with SAT or some other method?   
  The method I know is break your concave polygon in two or more convex polygons and then simply use SAT the same way you use for convex polygons.   ;  Thanks, I was thinking in school today about this, and thought of something like that but wasn't sure if it would work.  I'll start to learn the SAT, and then see if I can get it to work.  If I have troubles...I'll be back.  Thanks.   