The Marble Flip-Flop is a teeter-totter for marbles. It is a mechanical analog for an electronic flop-flop, or divide by two counter. a marble fed to this device will first go to one side, the next marble will go to the other side, hence the divide-by-two. This is scaled for 16mm marbles and a small nail is the axle. It may be stacked to make a binary counter. This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/fy0MJ0698MT