EQUIPMENT: A set of Double 6 or Double 12 dominoes.
SETUP: Turn all the dominoes face down. Appoint one player the Flipper. It is fairest if the Flipper does not play.
OBJECT: To find loops the fastest as they are turned up and thereby finish with the most dominoes.
LOOPS: A loop is a group of dominoes that can be formed into a closed loop, with each domino matching the two on either side, and no pair of numbers occurring more than once. The dominoes 1-4, 4-5 and 5-1 make a three-domino loop. The dominoes 2-0, 0-4, 4-5 and 5-2 make a four-domino loop. The largest loops consist of seven dominoes, or thirteen dominoes in a Double 12 set. Double dominoes count as loops in themselves: 3-3 is a one-domino loop.
PLAY: The Flipper turns dominoes face up, one by one at a regular rhythm, optionally to a musical beat. As soon as someone sees a loop, he or she calls "Loop!" At this point, the Flipper stops flipping and the player creates the loop he or she claims to have found. If the player has indeed identified a loop, he or she takes the dominoes and keeps them in a pile in front of himself or herself. Each loop should be kept in a separate pile. If the player has made a mistake and failed to identify a loop, he or she must return his or her smallest loop to the face-down stock, whereupon the Flipper scrambles them in. In either case, the Flipper now continues to flip up dominoes as before. No player may call "Loop!" while another player is forming a loop. If the Flipper is not playing, he or she is the judge of who called "Loop!" first when multiple players call it. If the Flipper is playing, everyone will have to be honorable.
SCORING: After all the dominoes have been formed into loops, the player with the most dominoes wins the game. There is a simple inductive proof that all the dominoes will end up in loops, as long as the highest suit in the set is an even number.
VARIANTS: Since everyone knows the last domino will form a Loop, you may wish to rule that the last loop is worth only two dominoes. You can also try playing with two Double 6 sets at once, if you want a longer game but would prefer shorter loops or have no Double 12 set.