The rules of Backgammon.
CONFIGURATION
Backgammon is a two-player game played on a board consisting of twenty-four narrow triangles called points. The triangles alternate in color and are grouped into four quadrants of six triangles each. The quadrants are referred to as the inner board and the outer board. They are separated from each other by a bar in the center of the board.
Figura 1. Un tablero con las piezas en su posición inicial. Una disposición alternativa es la inversa de la que se muestra aquí, con el tablero interno a la izquierda y el tablero externo a la derecha.
Los puntos están numerados para cada jugador comenzando desde el tablero interno de ese jugador. El punto más externo es el veinticuatro, que corresponde también al punto uno del oponente. Cada jugador tiene quince piezas de su propio color. La disposición inicial de las piezas es la siguiente: dos en el punto veinticuatro de cada jugador, cinco en el punto trece, tres en el punto ocho y cinco en el punto seis.
Ambos jugadores tienen su propio par de dados. Además, se utiliza un dado de doblaje, con los números 2, 4, 8, 16, 32 y 64 en sus caras, para llevar el registro de la apuesta actual de la partida.
OBJECTIVE OF THE GAME
The objective of the game is to move all your pieces to your own board and then remove them. The first player to remove all their pieces wins the game.
Figure 2. Direction of movement of the white pieces. The red pieces move in the opposite direction.
MOVEMENT OF THE PIECES
To begin the game, each player rolls a single dice. This determines who goes first and which numbers will be played. If the numbers are the same, both players roll again until they roll different numbers. The player who rolled the highest number now moves their pieces according to the numbers shown on both dice. After the first roll, players roll two dice and alternate turns.
The roll of the dice indicates how many points the player must move their pieces. Pieces always move forward , toward a lower-numbered point.
The following rules apply:
1. A checker may only move to an open point, one that is not occupied by two or more opposing checkers.
2. The numbers on the two dice represent separate moves. For example, if a player rolls 5 and 3, they may move one piece five spaces to an open spot and another piece three spaces to an open spot, or they may move the single piece a total of eight spaces to an open spot, but only if the intermediate spot (either three or five spaces from the starting spot) is also open.
Figure 3. Two ways in which White can play a roll of 5 and 3.
3. A player who rolls doubles plays the numbers shown on the dice twice. A roll of 6 and 6 means the player has four sixes to use, and may move any combination of pieces they choose to satisfy this requirement.
4. A player must use both numbers of a roll if it is legally possible (or all four numbers in the case of doubles). When only one number can be played, the player must play that number. If either number can be played but not both, the player must play the higher one. When neither number can be used, the player loses their turn. In the case of doubles, if not all four numbers can be played, the player must play as many as possible.
ATTACK & ENTER
A point occupied by a single checker of either color is called a blot. If an opposing checker lands on a blot, that checker is hit and placed on the bar.
Whenever a player has one or more checkers on the bar, their first obligation is to re-enter those checker(s) into the opponent’s home board. A checker is re-entered by moving it to an open point corresponding to one of the numbers rolled on the dice.
For example, if a player rolls a 4 and a 6, they may re-enter a checker on the opponent’s four-point or six-point, provided that the chosen point is not occupied by two or more of the opponent’s checkers.
Figure 4. If White rolls a 6 and a 4 with one checker on the bar, they must re-enter the checker on Red’s four-point, since Red’s six-point is not open.
If neither point is open, the player loses their turn. If a player can re-enter some of their checkers but not all, they must re-enter as many as possible and then forfeit the remainder of their turn.
Once a player has re-entered their last checker, any unused numbers on the dice must still be played, either by moving the checker that was re-entered or by moving a different checker.
MOVING TO REMOVE THE CHIPS FROM THE BOARD
Once a player has moved all fifteen of their checkers into their home board, they may begin bearing them off. A checker is borne off by rolling a number that corresponds to the point on which the checker rests, and then removing that checker from the board. Thus, rolling a 6 allows the player to bear off one checker from the six-point.
If there are no checkers on the point indicated by the roll, the player must make a legal move using a checker from a higher-numbered point. If there are no checkers on higher-numbered points, the player is permitted (and required) to bear off a checker from the highest point on which they have a checker. A player is not obligated to bear off a checker if a legal move is otherwise available.
Figure 5. White rolls a 6 and a 4 and bears off two checkers.
A player must have all of their checkers in their home board in order to begin bearing off. If a checker is hit during the bearing-off process, the player must return it to their home board before continuing to bear off. The first player to bear off all fifteen checkers wins the game.
FOLD
Backgammon is played for an agreed stake per point. Each game begins at one point. During the course of play, a player who feels they have a sufficient advantage may propose doubling the stakes. This can only be done at the beginning of their own turn, before rolling the dice.
A player who is offered a double may refuse, in which case they concede the game and pay one point. Otherwise, they must accept the double and continue playing for the higher stakes. The player who accepts a double becomes the owner of the doubling cube, and only they may offer the next double.
Subsequent doubles in the same game are called re-doubles. If a player declines a re-double, they must pay the number of points that were at stake before the re-double. Otherwise, they become the new owner of the cube and the game continues at twice the previous stakes. There is no limit to the number of re-doubles in a single game.
GAMMONS & BACKGAMMONS
At the end of the game, if the losing player has removed at least one piece, they only lose the value shown on the doubling dice (one point if there were no doubles). However, if the loser has not removed any of their pieces, they are ejected and lose double the value of the doubling dice. Or, worse yet, if the loser has not removed any of their pieces and still has a piece on the bar or the winner's board, they are ejected and lose triple the value of the doubling dice.
OPTIONAL RULES
The following optional rules are widely used:
-
Automatic doubles. If identical numbers are rolled on the first turn, the stakes are doubled. The doubling cube is set to 2 and remains in the center. Players often agree to limit the number of automatic doubles to one per game.
-
Beavers. When a player is doubled, they may immediately re-double (beaver) while retaining possession of the cube. The original doubler then has the option to accept or refuse, just as with a normal double.
-
The Jacoby Rule. Gammons and backgammons only count as a single game if no player has offered a double during the course of play. This rule speeds up the game by eliminating situations where a player avoids doubling in order to continue playing for a gammon
IRREGULARITIES
1. The dice must be rolled together and land flat on the surface of the right-hand section of the board. The player must re-roll both dice if a dice lands outside the right-hand board, lands on a piece, or does not land flat.
2. A turn is completed when the player collects their dice. If the move is incomplete or illegal, the opponent has the option of accepting the move as made or requiring the player to make a legal move. A move is considered to have been accepted when the opponent rolls their dice or offers a double to begin their own turn.
3. If a player rolls before their opponent has completed their turn by picking up the dice, the player's roll is void. This rule is generally waived whenever a move is forced or when there is no further contact between the opposing forces. 
