Self-working magic

Self-working magic is just that — self-working. After the set-up (sometimes, there's no set-up at all), the trick works completely by itself. All the magician has to do is follow a certain procedure, and everything will be good. Usually, self-working card tricks revolve around some mathematical principle, such as in the trick "Magical 13", where the spectator is asked to cut the deck 13 times, then split the deck into 13 piles. Upon revealing each pile, it is found that each pile contains the only cards of the same value (i.e., one pile has all four fours, the other pile has all four twos, etc.). This is based on the principle that beforehand, the deck is set up with all the suits in order. No matter how many times you cut the deck, the same cards will always be 13 cards away from each other.