I think it is an interesting game. Put the crabs on a record player. Turn the switch on and wait a few minutes. It is used for keeping one's balance. But if organisms go round and round, the semicircular canal doesn't work.
Crabs walk sideways.
That's how we can make crabs walk straight. Show the observer your coin. Tell him that you will make it disappear. After the observer has searched you, looking for the coin, tell him that you will make it appear from your mouth. Put the tip of your thumb of the arm that has the coin in it behind your front teeth.