The game is a marble path cut out of wood. The basic idea is that marbles go in the top, are directed around the paths by pivoting switches (flipping them around in the process), and eventually come out one of the bottom paths. The goal is to get it to come out a particular path.

For example, the game pictured here has two inputs, each of which goes into an alternator. These direct the marble down one path or the other, then flip so that they use the other path the next time. They then hit some part of he "latch", either forcing it to tip left or right, or else hitting the middle and going whichever way the last marble left the latch.

The final plan involves three separate puzzles of varying difficulty based around this idea.