Chopsticks is a hand game for two or more players, in which players extend a number of fingers from each hand and transfer those scores by taking turns to tap one hand against another. Chopsticks is an example of a combinatorial game, and is solved in the sense that with perfect play, an optimal strategy from any point is known.
This official set of rules is called rollover where five fingers are subtracted should a hand's sum exceed 5 as described below.
- Each player begins with one finger raised on each hand. After the first player turns proceed clockwise.
- On a player's turn, they must either attack or split, but not both.
- To attack, a player uses one of their live hands to strike an opponent's live hand. The number of fingers on the opponent's struck hand will increase by the number of fingers on the hand used to strike.
- To split, a player strikes their own two hands together, and transfers raised fingers from one hand to the other as desired. A move is not allowed to simply reverse one's own hands. If any hand of any player reaches exactly five fingers, then the hand is killed, and this is indicated by raising zero fingers.
- A player may revive their own dead hand using a split, as long as they abide by the rules for splitting. However, players may not revive opponents' hands using an attack. Therefore, a player with two dead hands can no longer play and is eliminated from the game.
- If any hand of any player reaches more than five fingers, then five fingers are subtracted from that hand. For instance, if a 4-finger hand strikes a 2-finger hand, for a total of 6 fingers, then 5 fingers are automatically subtracted, leaving 1 finger. Under alternate rules, when a hand reaches 5 fingers and above it is considered a "dead hand".
- A player wins once all opponents are eliminated (by each having two dead hands at once).
- There is no variation in which a player can kill their own hand.