Welcome to the Lego League challenge. Twenty thousand kids tried to solve this scenario using the Lego Mindstorms Robotic Invention System. The essence of Mindstorms is the RCX microcomputer brick, pioneered at the MIT Media Lab. Users program their robot's behavior on a PC and then transmit that information to an RCX brick. The brick, the size of a deck of cards, has input ports that connect to sensors and output ports that, in turn, can be connected to anything from wheels to cables to pulleys.