Ba
A ba 「場」 or wind round is a complete round of play, where each player is the dealer at least once barring any premature end game conditions. Each round of play is associated with a single cardinal direction and its corresponding wind tile. For the remainder of this article, the term round will refer to a wind round, although it is sometimes used to mean kyoku instead.
Normally, a match is played for an agreed-upon number of rounds. Traditionally, this was four rounds (an iichan 「一荘」), one for each wind. This is still common in Chinese variants. In modern Japanese play, a match is normally played for two rounds (a hanchan 「半荘」) or sometimes for only one round (a tonpuusen 「東風戦」). Some rules sets allow the match to extend into additional wind rounds if no player has met the goal score.
The first round in a match is always associated with east, and subsequent rounds follow in the standard mahjong order of south, west, and then north. Consequently, a tonpuusen consists of an east round only, and a hanchan is an east round and a south round. In exceedingly rare rulesets which allow the game to continue beyond four rounds, the rounds would repeat so that the fifth round would be east, the sixth south, and so on.
The major difference in the play rules between each of the rounds is that the round wind is a more valuable tile and can be used by any player to score the yakuhai yaku. Additionally, the conditions under which the match ends may vary depending on the round, with additional rounds usually having a form of sudden-death rule.
Hand designations
Every hand in the game has a designation, and it is attached to the wind round.
Deal rotation
A complete round gives each player the opportunity to be the dealer once. After each hand, the dealer may be permitted to repeat the hand with an additional honba counter. While this is subject to many variations, the most common rule is that a repeat occurs if the dealer wins the hand, is tenpai when an exhaustive draw occurs, or when an abortive draw occurs. A chombo also causes the hand to be replayed, but without a honba counter. Some variations provide that if the dealer commits a chombo, the deal does rotate.
When the deal rotates to the fourth time, back to the player who was originally the dealer, the round ends and either the game is over or a new round begins.
Game length
The total game length is dependent on the number of game rounds used and the rules pertaining to the end of games.
Additional rounds
In many rulesets, a goal score must be reached by at least one player for the game to end. If this score is not met by any player at the end of the normal rounds of the game, the game proceeds into an additional round, or enchousen 「延長戦」. This round is usually played as sudden death: the game end as soon as a player reaches the goal score. Usually, but not always, the game will also end at the end of the additional round regardless of score; and the game will not proceed into a second additional round.