How the display for one space works. The motor (not shown) tuns the cam which will raise the circle to one of three positions: raised, level and lowered.
Since the motor has 24 steps per revolution, we can use 9 of them to turn two cams, saving on motors. We cannot reduce this number to three, since we would need 27 steps per revolution to get all possible combinations for each row.
More detailed view of cams.
What the completed game may look like