Collision Detection

http://devmag.org.za/2009/04/13/basic-collision-detection-in-2d-part-1/

I am experimenting with the Zelle graphics module.  I coded up a little program that has colored balls bouncing around the screen.  They bounce off the walls but happily ignore each other.  I would like to implement some kind of primitive collision detection so that they bounce off each other.

Siri, remind me to work on this.

Edit:

I am amazed bordering on stupification that I was able to implement a crude version of collision detection.  Let's be honest, this is not a serious physics engine, but the balls do bounce off each other, which is all I really wanted.