Arimaa is played on an 8×8 square board. There are four trap squares which allow pieces to be captured. The two players, Gold and Silver, control sixteen pieces each:
Piece | Elephant | Camel | Horse | Dog | Cat | Rabbit |
---|---|---|---|---|---|---|
Number | 1 | 1 | 2 | 2 | 2 | 8 |
Symbols |
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The game can be won by:
A player loses if it is their turn and they have no legal moves. In addition, a player can forfeit by resigning voluntarily or (if a clock is being used) if he or she runs out of time.
The rows (ranks) are numbered from one to eight starting from the one closest to Gold. The columns (files) are called by the letters "a" through "h" starting from Gold's left. [a]
The game begins with an empty board. Gold places the sixteen gold pieces in any configuration on the first and second ranks. Silver then places the sixteen silver pieces in any configuration on the seventh and eighth ranks. Figure 1 shows one possible initial placement. Gold has the advantage of moving first but Silver has the advantage of being able to react to Gold's setup.
Most pieces move one square at a time forward, backward, left, or right. Rabbits can only move forward, left, or right.
[b]
Moving a piece one square is a step.
A turn consists of one to four steps.
After the setup phase is completed the players alternate turns with Gold moving first.
The steps in a turn can be used on four different pieces, all on the same piece, or any combination. A step can only be made into an unoccupied square.
A player may not pass his or her turn, and each turn must make a net change to the position.
Thus one cannot, for example, take one step forward and one step backward with the same piece as their only two steps of a turn.
Position exchange of two equal pieces in four steps does not change the position and is therefore not legal as well.
[c] Furthermore, one's turn may not create the same position with the same player to move as has been created twice before.
[d]
Some pieces are stronger than others.
Stronger pieces can
push,
pull, and
freeze weaker enemy pieces.
The order of pieces from strongest to weakest is: elephant, camel, horse, dog, cat, rabbit.
Stronger pieces can freeze weaker enemy pieces.
If a piece is next to a stronger enemy piece and it is not next to any friendly pieces, the weaker piece is frozen and cannot be moved.
[e]
For example, elephants can freeze camels because elephants are stronger than camels.
In Figure 3:
A piece's state of being frozen or unfrozen is recalculated after every step. If a player uses one or more steps to unfreeze a piece, [f] the newly unfrozen piece may be moved on later steps of the same turn. It is legal to use one piece to unfreeze a second piece which in turn is used to unfreeze a third piece.
Friendly pieces do not freeze each other.
At the cost of two steps, a stronger piece may push a weaker enemy piece.
First the weak piece moves one step forward, backward, left, or right into an empty square. Then the stronger piece moves into the square that was just vacated.
In Figure 4, the b6 horse can push the b7 cat:
At the cost of two steps, a stronger piece may pull a weaker enemy piece. First the stronger piece moves one step forward, backward, left, or right into an empty square. Then the weaker piece moves into the square that was just vacated.
In Figure 4, the g5 horse can pull the g6 cat:
In Arimaa every step must always be into an empty square. A push requires that the weak piece move to an empty square, while a pull requires that the strong piece move to an empty square. If there are no appropriate empty squares the piece in question may not be pushed or pulled.
A piece that is frozen may not push or pull another piece, but it can be pushed or pulled by another piece.
Equally strong pieces cannot push or pull each other.
Rabbits can be pushed or pulled backwards but they cannot move backwards voluntarily.
Friendly pieces cannot push or pull each other.
A piece may not push and pull simultaneously. That is, a player cannot use three steps to have one friendly piece move two different enemy pieces. It is perfectly legal to use two steps for one push or pull followed by another two steps for another push or pull. The same piece can push, pull, be pushed, or be pulled twice in the same turn. [g]
The board has four specially marked trap squares located at c3, c6, f3, and f6.
If a piece is on a trap square and it is not next to any friendly pieces it is immediately captured and permanently removed from the game.
There are no exceptions to this rule.
The capture scenarios can be classified into two categories:
Figure 5 illustrates several different ways of capturing.
Case 1: A piece moves onto a trap square with no adjacent allies and is immediately captured.
Case 2: One piece is on a trap square. It is only next to one other friendly piece. The friendly piece moves away, and the piece on the trap square is captured.
A push or pull always takes two steps. Both steps are always completed even if one of the steps results in a piece being captured.
Case 1: Suicidal Step |
b3 cat steps to c3 | cat is captured | ||
Case 1: Piece Pulled onto a Trap |
f3 camel pulls f2 horse | camel steps to e3 or f4 | horse steps to f3 | horse is captured |
Case 1: Piece Pushed onto a Trap |
c8 dog pushes c7 cat to c6 | cat steps to c6 | cat is captured | dog steps to c7 |
Case 1: Suicidal Pull |
(Not shown) Strong piece sacrifices itself to pull a weaker enemy piece |
Strong piece steps onto undefended trap square | Strong piece is captured | Weak piece moves as if there were no capture |
Case 1: Suicidal Push |
(Not shown) Strong piece sacrifices itself to push a weaker enemy piece |
Weak piece is pushed to some square | Strong piece steps onto an undefended trap square | Strong piece is captured |
Case 2: Ally Leaves Voluntarily |
g6 rabbit steps to g5 or h6 | g6 rabbit steps to g5 or h6 | f6 cat is captured | |
Case 2: Ally is Pulled Away |
g7 dog pulls g6 rabbit | g7 dog steps to f7, g8, or h7 | g6 rabbit steps to g7 | f6 cat is captured |
Case 2: Ally is Pushed Away |
g7 dog pushes g6 rabbit | g6 rabbit moves to g5 or h6 | f6 cat is captured | g7 dog moves to g6 |
Arimaa is played on an 8×8 square board. There are four trap squares which allow pieces to be captured. The two players, Gold and Silver, control sixteen pieces each:
Piece | Elephant | Camel | Horse | Dog | Cat | Rabbit |
---|---|---|---|---|---|---|
Number | 1 | 1 | 2 | 2 | 2 | 8 |
Symbols |
![]() ![]() |
![]() ![]() |
![]() ![]() |
![]() ![]() |
![]() ![]() |
![]() ![]() |
The game can be won by:
A player loses if it is their turn and they have no legal moves. In addition, a player can forfeit by resigning voluntarily or (if a clock is being used) if he or she runs out of time.
The rows (ranks) are numbered from one to eight starting from the one closest to Gold. The columns (files) are called by the letters "a" through "h" starting from Gold's left. [a]
The game begins with an empty board. Gold places the sixteen gold pieces in any configuration on the first and second ranks. Silver then places the sixteen silver pieces in any configuration on the seventh and eighth ranks. Figure 1 shows one possible initial placement. Gold has the advantage of moving first but Silver has the advantage of being able to react to Gold's setup.
Most pieces move one square at a time forward, backward, left, or right. Rabbits can only move forward, left, or right.
[b]
Moving a piece one square is a step.
A turn consists of one to four steps.
After the setup phase is completed the players alternate turns with Gold moving first.
The steps in a turn can be used on four different pieces, all on the same piece, or any combination. A step can only be made into an unoccupied square.
A player may not pass his or her turn, and each turn must make a net change to the position.
Thus one cannot, for example, take one step forward and one step backward with the same piece as their only two steps of a turn.
Position exchange of two equal pieces in four steps does not change the position and is therefore not legal as well.
[c] Furthermore, one's turn may not create the same position with the same player to move as has been created twice before.
[d]
Some pieces are stronger than others.
Stronger pieces can
push,
pull, and
freeze weaker enemy pieces.
The order of pieces from strongest to weakest is: elephant, camel, horse, dog, cat, rabbit.
Stronger pieces can freeze weaker enemy pieces.
If a piece is next to a stronger enemy piece and it is not next to any friendly pieces, the weaker piece is frozen and cannot be moved.
[e]
For example, elephants can freeze camels because elephants are stronger than camels.
In Figure 3:
A piece's state of being frozen or unfrozen is recalculated after every step. If a player uses one or more steps to unfreeze a piece, [f] the newly unfrozen piece may be moved on later steps of the same turn. It is legal to use one piece to unfreeze a second piece which in turn is used to unfreeze a third piece.
Friendly pieces do not freeze each other.
At the cost of two steps, a stronger piece may push a weaker enemy piece.
First the weak piece moves one step forward, backward, left, or right into an empty square. Then the stronger piece moves into the square that was just vacated.
In Figure 4, the b6 horse can push the b7 cat:
At the cost of two steps, a stronger piece may pull a weaker enemy piece. First the stronger piece moves one step forward, backward, left, or right into an empty square. Then the weaker piece moves into the square that was just vacated.
In Figure 4, the g5 horse can pull the g6 cat:
In Arimaa every step must always be into an empty square. A push requires that the weak piece move to an empty square, while a pull requires that the strong piece move to an empty square. If there are no appropriate empty squares the piece in question may not be pushed or pulled.
A piece that is frozen may not push or pull another piece, but it can be pushed or pulled by another piece.
Equally strong pieces cannot push or pull each other.
Rabbits can be pushed or pulled backwards but they cannot move backwards voluntarily.
Friendly pieces cannot push or pull each other.
A piece may not push and pull simultaneously. That is, a player cannot use three steps to have one friendly piece move two different enemy pieces. It is perfectly legal to use two steps for one push or pull followed by another two steps for another push or pull. The same piece can push, pull, be pushed, or be pulled twice in the same turn. [g]
The board has four specially marked trap squares located at c3, c6, f3, and f6.
If a piece is on a trap square and it is not next to any friendly pieces it is immediately captured and permanently removed from the game.
There are no exceptions to this rule.
The capture scenarios can be classified into two categories:
Figure 5 illustrates several different ways of capturing.
Case 1: A piece moves onto a trap square with no adjacent allies and is immediately captured.
Case 2: One piece is on a trap square. It is only next to one other friendly piece. The friendly piece moves away, and the piece on the trap square is captured.
A push or pull always takes two steps. Both steps are always completed even if one of the steps results in a piece being captured.
Case 1: Suicidal Step |
b3 cat steps to c3 | cat is captured | ||
Case 1: Piece Pulled onto a Trap |
f3 camel pulls f2 horse | camel steps to e3 or f4 | horse steps to f3 | horse is captured |
Case 1: Piece Pushed onto a Trap |
c8 dog pushes c7 cat to c6 | cat steps to c6 | cat is captured | dog steps to c7 |
Case 1: Suicidal Pull |
(Not shown) Strong piece sacrifices itself to pull a weaker enemy piece |
Strong piece steps onto undefended trap square | Strong piece is captured | Weak piece moves as if there were no capture |
Case 1: Suicidal Push |
(Not shown) Strong piece sacrifices itself to push a weaker enemy piece |
Weak piece is pushed to some square | Strong piece steps onto an undefended trap square | Strong piece is captured |
Case 2: Ally Leaves Voluntarily |
g6 rabbit steps to g5 or h6 | g6 rabbit steps to g5 or h6 | f6 cat is captured | |
Case 2: Ally is Pulled Away |
g7 dog pulls g6 rabbit | g7 dog steps to f7, g8, or h7 | g6 rabbit steps to g7 | f6 cat is captured |
Case 2: Ally is Pushed Away |
g7 dog pushes g6 rabbit | g6 rabbit moves to g5 or h6 | f6 cat is captured | g7 dog moves to g6 |