Some time ago I had a great idea: I'm going to make two robots. One will be an obstacle avoider and its job will be just wander around with its big head. The other bot will then try to catch it and hit the head with a hammer. Tracking would be done with infrared leds and phototransistors. For the time being I've pretty much completed the first part and posted Head. Head already has infrared leds on its head so next thing would be building an infrared tracker.