2D Physics game using sprites

Hello.

I am trying to build a game that uses 2D sprites, with physics that limit themselves to 2 axes, identical to what one would be able to achieve using Box2D or Chipmunk.

Now, what I'm hoping to build is a physics-based platformer that involves some very weird use of boxes and spheres. To make my explanation easier, I'm going to link you to a popular title (popular because they made a sequel) called Werebox:

http://www.bubblebox.com/play/puzzle/1660.htm

The implementation for the physics would be the same, so I'm going to limit my question to just that: How can I get this kind of a system going using Unity3D? I know for sure that I can use sprites and what not and get the 2D interactions working in no time, but what about the physics?

Thankyou for your help! :)