My students built and programmed these for the Robofest competition. We won our regional and are advancing to the Worlds. It's built from Lego NXT hardware with a few aftermarket sensors. All the coding is done with RobotC. The game simulates a disaster rescue. The Kleenex boxes are rubble and the silver balls are injured victims. Ball locations, table dimensions, and table alignment are variable, so the robots have to be fairly smart.