Knock-off uses the frenzied flipping of two electrical panic buttons by each of two contestants as competition. Object of button play is to direct Big Bopper, a grinning 6 armed ball-shaped robot, as he moves to knock off your opponent's fall guy before he can knock off yours. Big Bopper runs across what looks like a raised bridge and the two fall guys are at either end. Wires from switches for control run along outside bottom edge of the bridge walls. The toy is battery operated.