Backgammon - Object of the Game
The object of the game is for each player to bring all his checkers into his home board, and then to bear them off the board. The first player to clear all his checkers off the board is the winner.
Playing the Game
Backgammon is a game for two players, played on a board of twenty-four narrow triangles called points. Each player has fifteen stones of one color (light or dark) that are placed along the boards 24 points. Points alternate in color and are grouped into four quadrants of six points each. Quadrants are referred to as a players home board and outer board. The board is divided in half by a center partition called the bar. All points on a backgammon board are distinguished by numbers. A players outermost point is the twenty-four point, which is also his opponents one point. A doubling cube, with the numbers 2, 4, 8, 16, 32, and 64, is used to keep track of the current stake of the game.
To start the game, each player rolls a single dice. This determines both the player to go first and the numbers to be played. If equal numbers come up, then both players roll again until they roll different numbers. The player who throws the highest number moves first according to the number displayed on the dice. After the first roll, the players throw both dice and alternate turns. The roll of the dice indicates how many points (or pips) a player can move his stones. Stones are always moved forward, to a lower-numbered point. The following rules apply: A stone can only be moved to an open point (one not occupied by two or more opposing stones).
The numbers on the two dice constitute separate moves. For example, if a player rolls 5 and 3, he may move one stone five spaces to an open point and another stone three spaces to an open point, or he may move the one stone a total of eight spaces to an open point, but only if the intermediate point (either three or five spaces from the starting point) is also open. A player who rolls doubles plays the numbers shown on the dice twice. A roll of 6 and 6 means that the player has four sixes to use, and he may move any combination of stones he feels appropriate to complete this move. A player must use both numbers of a roll if legally possible (and all four numbers of a double). When only one number can be played, the player must play that number. If either number can be played, but not both, a player must play the higher one. When either number cant be used, a player loses his turn. In the case of doubles, when all four numbers cant be played, a player must play as many numbers as he can.
Hitting and Entering
A point occupied by a single stone of either color is called a blot. If an opposing stone lands on a blot, the blot is hit and placed on the bar. Anytime a player has one or more stones on the bar, his first obligation is to enter that stone(s) into the opposing home board. A stone is entered by moving it to an open point corresponding to one of the numbers on the rolled dice. For example, if a player rolls 4 and 6, he may enter a stone onto either the opponents four point or six point, so long as the prospective point is not occupied by two or more of his opponents stones. If neither of the points is open, the player loses his turn. If a player is able to enter some but not all of his stones, he must enter as many as he can and then forfeit the remainder of his turn. After the last of a players stones has been entered, any unused numbers on the dice must be played.
Once a player has moved all of his fifteen stones into his home board, he can begin bearing off. A player bears off a stone, by rolling a number that corresponds to the point on which the stone resides, and then removing that stone from the board. If there is no stone on the point indicated by the roll, the player must make a legal move using a stone on a higher-numbered point. If there are no stones on the higher-numbered points, the player can remove a stone from the next highest point. A player is under no obligation to bear off if he can make an otherwise legal move. A player must have all of his active stones in his home board in order to bear off. If a stone is hit during the bear-off process, the player must bring that stone back to his home board before continuing to bear off.
The Doubling Cube
Backgammon is played for an agreed wager (or number of points in the tournament play). During the course of the game, a player who feels he has a sufficient advantage may propose doubling his stakes. He may do so, only at the start of his turn, and before he has rolled the dice. A player who is offered a double may refuse, in which case he concedes the game and pays the original wager. Otherwise, he must accept the double and play on for the new higher stakes. A player who accepts a double becomes the owner of the cube and only he may make the next double. Subsequent doubles in the same game are called redoubles. If a player refuses a redouble, he must pay the wager that was at stake prior to the redouble. Otherwise, he becomes the new owner of the cube and the game continues at twice the previous stakes. Redoubles can increase upto 64 times the original wager.
Playing with beavers
An optional rule in Single Game Mode which says that when a player is doubled, he may immediately redouble (beaver) while retaining possession of the doubling cube. The original doubler has the option of accepting or refusing as with a normal double.
The Jacoby Rule makes gammons and backgammons count for their respective double and triple points only if there has been at least one use of the doubling cube in the game. This encourages a player with a large lead in a game to double, and thus likely end the game, rather than see the game out to its conclusion in hopes of a gammon or backgammon. The Jacoby Rule is widely used in money play, but is not used in match play.
The Crawford Rule makes match play much more fair for the player in the lead. If a player is one point away from winning a match, his opponent has no reason not to double; after all, a win in the game by the player in the lead would cause him to win the match regardless of the doubled stakes, while a win by the opponent would benefit twice as much if the stakes are double. Thus there is no advantage towards winning the match to being one point shy of winning, if one's opponent is two points shy!
To remedy this situation, the Crawford Rule requires that when a player becomes one single point short of winning the match, neither player may use the doubling cube for a single game, called the Crawford Game. As soon as the Crawford Game is over, any further games use the doubling cube normally.
Not quite as universal as the Jacoby Rule, the Crawford Rule is widely used and generally assumed to be in effect for match play.
When automatic doubles are used, any re-rolls that players must make at the very start of a game (when each player rolls one die) have the side-effect of causing a double. Thus, a 3-3 roll, followed by a re-roll of 5-5, followed by a re-roll of 1-4 that begins the game in earnest, will cause the game to be played from the start with 4-times normal stakes. The doubling cube stays in the middle, with both players having access to it. The Jacoby Rule is still in effect.
Automatic doubles are common in money games (upon agreement). They are never used in match play.
Known variant - all same but 6-6 triples rather than doubles stakes.
Gammons and Backgammons
At the end of the game, if the losing player has borne off at least one stone, he loses only the value showing on the doubling cube (the original wager or one point if there have been no doubles). However, if the loser has not borne off any of his stones, he is gammoned and loses twice the value of the doubling cube. More so, if the loser has not borne off any of his stones and still has a stone on the bar or in the winners home board, he is backgammoned and loses three times the value of the doubling cube.