Backgammon is a board game for two
players in which the playing pieces are moved according to the roll
of dice. A player wins by removing all of his pieces from the
board. There are many variants of backgammon, most of which share
common traits. Backgammon is a member of the tables family, one of
the oldest classes of board games in the world.
Although luck plays an important role, there is a large scope for
strategy. With each roll of the dice a player must choose from
numerous options for moving his checkers and anticipate possible
counter-moves by the opponent. Players may raise the stakes during
the game. There is an established repertory of common tactics and
occurrences.
Like chess, backgammon has been studied with great interest by
computer scientists. Owing to this research, backgammon software
has been developed capable of beating world-class human
players.
Rules
Backgammon playing pieces are known variously as checkers, stones,
men, counters, pawns, or chips.
The objective is to remove (bear off) all of one's own checkers
from the board before one's opponent can do the same. The checkers
are scattered at first and may be blocked or hit by the opponent.
As the playing time for each individual game is short, it is often
played in matches, where victory is awarded to the first player to
reach a certain number of points.
Setup
Each side of the board has a track of 12 long triangles, called
points. The points are considered to be connected across one edge
of the board, forming a continuous track in the shape of a
horseshoe, and are numbered from 1 to 24. Each player begins with
two checkers on his 24-point, three checkers on his 8-point, and
five checkers each on his 13-point and his 6-point. The two players
move their checkers in opposing directions, each from his own
24-point towards his 1-point.
Points 1 through 6 are called the home board or inner board, and
points 7 through 12 are called the outer board. The 7-point is
referred to as the bar point, and the 13-point as the mid
point.
Movement
A Short Treatise on the Game of Backgammon, by Edmond Hoyle
To start the game, each player rolls one die, and the player with
the higher number moves first using both the numbers shown. Both
dice must land completely flat on the right hand side of the
gameboard. The players then alternate turns, rolling two dice at
the beginning of each turn.
After rolling the dice a player must, if possible, move his
checkers according to the number of pips shown on each die. For
example, if the player rolls a 6 and a 3 (notated as "6-3"), that
player must move one checker six points forward, and another or the
same checker three points forward. The same checker may be moved
twice as long as the two moves are distinct: six and then three, or
three and then six. If a player rolls two of the same number,
called doubles, that player must play each die twice. For example,
upon rolling a 5-5 that player may move up to four separate
checkers forward five spaces each. For any roll, if a player can
move both dice, that player is compelled to do so. If a player
cannot move either die in a roll, given the position of his
checkers then that turn is over and the turn passes to the
opponent.
If it is possible to move either die, but not both, the higher
number must be played. For example if a player rolls 6-3 and can
only move a 6 or a 3, the 6 being the bigger number must be moved;
if it is possible to move the 3 but not the 6 then the 3 is played.
Further, if one die is unable to be moved, but such a move is made
possible by the moving of the other die, that move is
compulsory.
For example, in the case of a 6-3 roll, no moves of 3 are possible
by any checker. However there are 2 moves of a 6, with checker A or
checker B. If checker A is moved 6, the 3 still cannot be played.
If checker B is moved 6, a 3 now may be played. The rules state
that the player is forced into moving checker B 6 points, and then
3. In short, the rules compel a player to exhaust every option
available to complete both die moves where possible.
In the course of a move, a checker may land on any point that is
unoccupied or is occupied only by a player's own checkers. It may
also land on a point occupied by exactly one opposing checker, or
"blot". In this case, the blot has been hit, and is placed in the
middle of the board on the bar that divides the two sides of the
playing surface. A checker may never land on a point occupied by
two or more opposing checkers; thus, no point is ever occupied by
checkers from both players simultaneously.
Checkers placed on the bar re-enter the game through the opponent's
home board. A roll of 2 allows the checker to enter on the
23-point, a roll of 3 on the 22-point, and so forth. A player may
not move any other checkers until all checkers on the bar belonging
to that player have re-entered the game.
When all of a player's checkers are in that player's home board,
that player may start removing them; this is called bearing off. A
roll of 1 may be used to bear off a checker from the 1-point, a 2
from the 2-point, and so on. A die may not be used to bear off
checkers from a lower-numbered point unless there are no checkers
on any higher points. For example if a player rolls a 6 and a 5,
but has no checkers on the 6-point, though 2 checkers remain on the
5-point, then the 6 and the 5 must be used to bear off the 2
checkers from the 5-point. When bearing off, a player may also move
a lower die roll before the higher even if that means 'the full
value of the higher die' is not fully utilized. For example, if a
player has exactly 1 checker remaining on the 6-point, and rolls a
6 and a 1, the player may move the 6-point checker 1 place to the
5-point with the lower die roll of 1, and then bear that checker
off the 5-point using the die roll of 6; this is sometimes useful
tactically.
If one player has not borne off any checkers by the time that
player's opponent has borne off all fifteen, then the player has
lost a gammon, which counts for double a normal loss. If the losing
player has not borne off any checkers and still has checkers on the
bar or in the opponent's home board, then the player has lost a
backgammon, which counts for triple a normal loss.
