The following rules apply to official Arimaa games that are played for ranks, tournaments, contests, championships, etc.
Match Game Requirements
Game must be recorded. All moves made in the game must be recorded using the Notation for Recording Arimaa Games
Time controls must be used. An official Arimaa match must be played with some form of Arimaa Time Control. Details of time controls are given below.
The time control must be chosen to allow a game to reach at least 80 moves.
If a game is stopped due to reaching the time control limit then the winner is determined by scoring the game as follows: the player who currently has or most recently had more pieces left after the completion of a turn wins. Otherwise the player to move second (silver) wins.
A player may resign at any time to end the match. However, resigning is highly discouraged. Continuing a game to a natural finish is highly encouraged.
Time ControlsThe Arimaa time controls were chosen to achieve the following: 1. Keep the game moving, by not allowing a player to take forever to make a move and bore the spectators. 2. Allow a lot of flexibility in specifying the time controls. 3. Allow for a fixed upper limit on the total game time for practical reasons. 4. Attempt to prevent a player from losing the game due to time while imposing these time limits. 5. Preserve the quality of the game while imposing these time limits. 6. Allow for the most common time controls used in Chess. Thus the Arimaa time controls support all the common time controls used in Chess and more. The time control used for Arimaa is specified as: M/R/P/L/G/T where M is the number of minutes:seconds per move; required R is the number of minutes:seconds in reserve; required P is the percent of unused move time that gets added to the reserve; optional defaults to 100 L is the number of minutes:seconds to limit the reserve; 0 means no limit; optional; defaults to 0 G is the number of hours:minutes after which time the game is halted and the winner is determined by score. G can also be specified as the maximum number of moves by ending with 't'; 0 means no limit; optional; defaults to 0 T is the number of minutes:seconds within which a player must make the move; 0 means no limit; optional; defaults to 0 On each turn a player gets a fixed amount of time per move (M) and there may be some amount of time left in the reserve (R). If a player does not complete the move within the move time (M) then the time in reserve (R) is used. If there is no more time remaining in reserve and the player has not completed the move then the player automatically loses. Even if there is time left in the move or reserve, but the player has not made the move within the maximum time allowed for moves (T) then the player automatically loses. If a player completes the move in less than the time allowed for the move (M), then a percentage (P) of the remaining time is added to the players reserve. The result is rounded to the nearest second. This parameter is optional and if not specified, it is assumed to be 100%. An upper limit (L) can be given for the reserve so that the reserve does not exceed L when more time is added to the reserve. If the initial reserve already exceeds this limit then more time is not added to the reserve until it falls below this limit. The upper limit for the reserve is optional and if not given or set to 0 then it implies that there is no limit on how much time can be added to the reserve. For practical reasons a total game time (G) may be set. If the game is not finished within this allotted time then the game is halted and the winner is determined by scoring the game. This parameter is optional and if not given (or set to 0) it means there is no limit on the game time. Also instead of an upper limit for the total game time, an upper limit for the total number of turns each player can make may be specified by adding the letter 't' after the number. After both players have taken this many turns and the game is not finished the winner is determined by scoring the game. For games which use a time per move of less than 1 minute, both players are always given 1 minute of time to setup the initial position in the first move of the game. If the setup is not completed in 1 minute then the reserve time (R) is also used. The unused time from the setup move is not added to the reserve time. Example 1: 0/5 means 0 minutes per move with 5 minutes in reserve (per player). This is equivalent to G/5 in Chess; it means each player has a total of 5 minutes of time to play. If a player runs out of time before the game is over, the player loses. This is known as Blitz or "Sudden Death" time control in Chess. Example 2: 0:12/5 means 12 seconds per move with 5 minutes in reserve and all of the unused time from each move is added to the reserve time. It is similar to "5 12" in Chess which means "Game in 5 minutes with a 12 second increment". After each move 12 seconds is added to the remaining time. This is known as Incremental time control in Chess. Example 3: 3/0 means 3 minute per move and no reserve time, but 100 percent of the unused time for each move is added to the reserve. This guarantees that each player will make at least 40 moves in 2 hours. This is similar to the "40/2" Quota System time control used in Chess. Example 4: 0:30/5/100/3 means 30 seconds per move with 5 minutes in reserve and 100% of the unused time from each move is added to the reserve time. When the reserve already exceeds the limit, more time is not added to it. When the reserve falls below 3 minutes more time can be added to it, but the reserve is capped at 3 minutes. Example 5: 4/2/50/10/6 This means 4 minutes per move with a starting reserve of 2 minutes. After the move 50% of the time remaining for the move (rounded to the nearest second) is added to the reserve such that it does not exceed 10 minutes. There is a limit of 6 hours for the game after which time the game is halted and the winner is determined by score. Example 6: 4/4/100/4/6 This means 4 minutes per move and a starting reserve of 4 minutess. 100% percent of the unused move time gets added to the reserve such that it does not exceed 4 minutes. There is a time limit of 6 hour for the game after which the winner is determined by score. Example 7: 4/4/100/4/90t This is the same as above, but the game ends after both players have made 90 moves. Thus it ends after move 90 of silver is completed. Example 8: 4/4/100/4/90t/5 This is the same as above, but the players may not take more than 5 minutes for each turn even if there is still time remaining in reserve. Different time units for any of the time control fields can be specifed by adding one of the following letters after the numbers. In such cases the letter serves as the seperator and : should not be used. s - seconds m - minutes h - hours d - days For example: 24h5m10s/0/0/0/60d means 24 hours, 5 minutes and 10 seconds per move and the game must end after 60 days. Such a time control may be used in a postal type match. The game time parameter (G) can also be specified in terms of maximum number of turns each player can make by adding the letter t after the number.
The rules for official matches are subject to change by the game desingers as more experience is gained with the game. These rules are effective July 1st, 2008.
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