I built this robot last year for a science fair project. It is really very simple, but has become more complicated as time went by. I started with simple bump sensors, as can be seen on the front and back. Later came an optical encoder system, which can also be seen. I have added, although not shown, another optical circuit that acts as a power switch, to shut the robot down in a dark area. I did this only to dabble with behavioral processing. The controller is a BSII. My code was mostly based on subroutines, and printed out ranged from 1 to about 4 pages long. I only say this because I would like to know how other people write programs. Perhaps what I like best about the robot is the chasis. It is standard aluminum stock, but I took care in making sure it can be adjusted and redesigned. For example, the optical encoder hardware can be adjusted for a thick or thin disk, the gear box can be moved forward or backwards, and the sensitivity of the bumpers can be adjusted, to name a few. My site www.geocities.com/isenbergdoug/isenbergrobotics.html has information on other robotic projects I am working on, as well as this one. Email: dri103@psu.edu