You start out with balls located in the center of iron bars. There are color-coded slots on the side that match one of the colors of each ball. Your job is to turn those iron bars, so that the ball can get into its designated slot.
There will come a time when the bar blows up, though, so be careful! Don't let the balls hit the bars too many times! And don't send the balls on an off-board path. That's not good.