It challenges robots to force their opponents out of a 5-foot diameter circular ring. Because the rules are straightforward, Sumo robots can be fairly simple. Tom Rowley's Web site shows how to build a simple Sumo robot. Sine Robotics makes it easy to build a maze running or line following robot. Except for batteries, it has everything needed to build a reliable robot.
Some competitions use standard computer modules.
In the MIT 6.270 Lego robot competition, the students use Dr. Fred Martin's Handy Board. This computer has a Motorola 68HC11 microprocessor and includes motor drivers, sensors, and an LCD display. It runs Interactive C, a multi-tasking development system that includes functions for controlling the motors and reading sensors. As a result, it allows students to begin writing applications without worrying about low-level control programming. They focus attention on the mechanical parts of a design.