Robot-sumo, or pepe-sumo, is a sport in which two robots attempt to push each other out of a circle (in a similar fashion to the sport of sumo). The robots used in this competition are called sumobots.
The engineering challenges are for the robot to find its opponent (usually accomplished with infrared or ultra-sonic sensors) and to push it out of the flat arena. A robot should also avoid leaving the arena, usually by means of a sensor that detects the edge.
The most common "weapon" used in a sumobot competition is an angled blade at the front of the robot, usually tilted at about a 45-degree angle towards the back of the robot. This blade has an adjustable height for different tactics.