Backgammon is a two-player board game played with counters and dice. It dates back nearly 5,000 years to the regions of Mesopotamia and Persia. The earliest record of backgammon itself dates to 17th-century England, being descended from the 16th-century game of Irish.

For an introduction to learning backgammon see https://ukbgf.com/wp-content/uploads/An-Introduction-to-Backgammon-September-2019-V2.1-final.pdf.

Rules

The object of the game is for each player to bring all their checkers into their home board, and then to bear them off the board. The first player to get all their checkers off the board is the winner.

Each player starts with 15 checkers setup as shown in the starting diagram above.

From the perspective of the player playing with the white pieces (player 1) their home is on the bottom right (currently points 1-6) and their pieces moves anti-clockwise around the board. Whereas the black home (player 2) is on the top right (currently points 19-24) and their pieces move in the other direction (clockwise).

The points shown on the board are for the active player - and will swap each turn, such that a players checkers move from point 24 to point 1. This helps within keeping the notation consistent.

Pieces can be captured if they are landed upon by the opponent, however a piece cannot move onto a square if that square in occupied by 2 or more pieces of the opponent.

A captured piece must be placed back into the opponent's home (with the dice roll limiting where it can land 1-6 for the home spots) before that player can move a piece or take a piece off the board.

It is possible for a player to have no legal actions available once they have rolled the dice, in this situation they must just end the turn.

There is a special rule of 'gin' that states that "If the player whose time has run out is certain to win the match, no matter what is rolled in the remainder of the game, including an already rolled legal throw, the player is still declared the winner of the match."

Platform Gameplay

There is a preference which a user can set ("Play Forced Actions") to automatically play moves and end their turn if their is no choice to be made. This is a common feature on other Backgammon websites.

A turn in Backgammon is made up three phases, rolling the dice, moving pieces, and confirming. The rolling of dice happens automatically at the start of a turn, immediately giving the player the chance to make moves. A player may freely undo their moves back until the dice roll. This is achieved by clicking the 'UNDO' button on the game board. Undos are similar to takebacks, but undos do not require permission from your opponent and are allowed in tournament play. Due to the ability to undo parts of a turn there is a need to confirm the end of a turn. This is achieved by clicking on the dice or hitting the space-bar key.

Limitations

• There is no support for multi-point Backgammon and games where a 'Doubling Cube' is used. It is the intention to add this extended gameplay mode in due course.
• PlayStrategy requires a cap on the total 'plies' a game can have. This is set to 1000, which is an unlikely number to reach if both players are playing to win, but it is theoretically possible to hit even if this is true. If a game reaches 1000 plies, it will be automatically ended and marked as a draw. This is true for all variants, although is more notable in Backgammon, which has no official rules to permit a draw. It is the intention to look into alternatives for Backgammon so as to never have a situation where a draw can occur.

For context, a ply is any action within the game, and for Chess the terms ply/move/turn are all equivalent. In PlayStrategy's implementation of Backgammon, a normal turn consists of 4 plies (Rolling the dice, moving a piece with the first dice, moving a piece with the second dice, and confirming the end of turn). However, the number of plies in a turn is flexible depending on if a double is rolled and if there are legal moves, and so can range from a minimum of 2 and maximum of 6.