The Annual Computer Poker Competition started with heads-up (i.e., two player) poker games. As techniques in the two player game improved and as the popularity of poker rose, interest in ring games (games with more than two players) also increased. In 2008, the Annual Computer Poker Competition introduced its first ring game: 6-player limit Texas Hold'em. Subsequent years switched to 3 players.
The competition uses standard rules for its ring games. Generally the rules for each hand of a ring game are similar to a heads-up game. The most notable difference is the betting order. More specifically, there will be a button, a "small blind" to the left of the button, and a "big blind" to the left of the small blind. As per their names, these players make forced bets of the small blind and big blind, respectively. The action starts to the left of the big blind pre-flop, and it starts to the left of the button on all other betting rounds.
As in heads-up limit Texas Hold'em, bets are of a fixed size and there is a maximum of 4 bets per round, even if it is heads-up.