Let's Make Robots!

IR Tank Battle Bots

I want to make 2 robots out of Lego with tank treads and a turret that will shoot an "Ion Cannon" at the other bot. When hit, the bot will rock its wheels, make a sound and a point given to the victor. I want these to battle in an arena of fish tank gravel, and the turrets only will have left-right degrees of freedom in a maximum of a 180 degree spread (powered by a servo)