USED GOOD: A steel ball is set moving down a ramp towards the base, on which a tower of barrels must be built. Each barrel has a protruding shape on top and a different indented shape on the bottom, to allow some combinations of barrels to interlock. Players must find the correct barrels as quickly as possible and stack as many as they can before the ball arrives. When they have completed as much of the tower as they are able, they shut a gate to stop the ball from reaching the barrels. If they are too slow, the whole tower will fall over when hit by the ball. Players take it in turns to see how high a tower they can build.