# Backgammon

Backgammon is a traditional Saxon game opposing two players. There exist a lot of ancestors everywhere around the world and they are probably coming from Ancient Rome or even earlier.

The objective is to take all your checkers out of the board, before your opponent does the same. One plays with a pair of classic six-faced dice and with a specific board composed of 24 squares called points in Backgammon.

## Game rules

### The board

The backgammon board is composed of 24 points, divided into 4 quadrants of 6 points each, or, otherwise seen, two lines of 12 points.

Points are numbered clockwise, starting at 1 on the bottom right, 12 on bottom left, 13 on top left, and 24 on top right.

Another way to describe it is to say that the track forms a horse iron open on the right.

Checkers of the first player will go through the board from point 24 to point 1, while those of the second player will go in the other direction, from point 1 to 24.

Normally, the two right quadrants are called interior quadrants, and the two on the left the exterior quadrants. As well, each player's camp is the above or below part containing their starting point (on top for the first player, containing point 24, and the bottom for the second player, containing point 1).

Finally, the *bar* separates the two camps.

Each player initially owns 15 checkers, placed as follows: 2 checkers on point 24, 3 checkers on point 8 and 5 checkers on points 13 and 6 for the first player, and symetrically, 2 checkers on point 1, 3 checkers on point 17 and 5 checkers on points 12 and 19 for the second player.

### Movements

At each turn, dice are rolled and one or two checkers are advanced by the number of points indicated by the dice.

One can move the same checker twice in a row, as long as each move is run in a clearly distinguishable way one after the other. Thus, for example, if you rolled 3 and 6, you can't advance a checker directly by 9 points; but you can advance it first by 3 points and then by 6, or the opposite, first by 6 points and then by 3, depending on your choice and your possibilities.

One can of course also advance a checker by 3 points and then another by 6 or conversely. The order in which dice are played is indifferent.

It is very important to distinguish each move because everything isn't allowed (see further below). In the previous example, it may be the case that the checker you want to move could advance by 9 points directly, but couldn't neither advance by 3 nor 6 points, in which case you can't touch that checker this turn.

You will have to move another checker if you can. It could happen sometimes that you are forced to skip your turn or a part of it because no moves are possible.

When rolling double, dice are played twice instead of just once. Thus, for example, by rolling 5 5, you can make four moves of 5 points each instead of just two.

In such a case, you can move four times the same checker, or four different checkers, at your choice.

### Barriers and captures

When moving a checker, you can make it arrive on a free point, or on a point already occupied by one or more of your checkers.

You can also move a checker on a point occupied by *a single checker of your opponent*, in which case it is *captured*. A captured checker is placed in the bar and must re-enter the board before any other movement.

You can't move any checker on the board as long as you still have one or more of your checkers captured by your opponent on the bar.

A 1 on a die allows to make a checker re-enter on point 1 or 24, a 2 on point 2 or 23, etc. of course in your camp, points 19 to 24 for the first player and points 1 to 6 for the second player.

You aren't allowed to place a checker on a point already occupied by two or more checkers owned by your opponent; the latter are forming a *barrier*.

It is therefore impossible for a point to have tokens of both players at the same time.

### Removing checkers

When all your checkers have been brought to your interior quadrant, respectively in points 1 to 6 and 19 to 24, the removal phase can start.

A 1 on the die allows to remove a checker from point 1 or 24, a 2 on the die from point 2 or 23, etc.

If there is no checker on the exact required point, you can remove checkers from the board from more advanced points, but only if there is no checker on previous points.

For example with a 4 on the die, you can always remove a checker from point 4; you can also remove a checker from points 3, 2 or 1, but only if none of your checkers are on points 4, 5 or 6.

In this case, this implies that all dice points may not be used completely. Such unused dice points are lost.

If one of your checkers is captured during your removal phase, you are no longer allowed to remove checkers from the board until the captured checker has re-entered the board and reached again the last interior quadrant.

### Winning, gammon and backgammon

To win the round, you must remove all your checkers from the board. Thus, a victory point is counted. A complete game is usually played up to 3, 5 or 7 points, which are reached in several rounds (at least 3).

Given that the randomness of the dice takes an important part in the game, it is rather unusual and inappropriate to finish a complete game in a single round.

If you manage to remove all your checkers from the board while your opponent didn't remove any, two victory points are counted instead of just one. This is called *gammon*.

If you finish while your opponent still has checkers on the bar or in his first interior quadrant, whether he already removed checkers or not, this gives a *backgammon* which is worth three victory points.

### Doubling die

At any time, you are allowed to request a doubling of the stake. If your opponent accepts, the game continues; if he refuses, then he immediately loses the round.

By doing it, the round will be worth two victory points instead of just one, and therefore the value of a gammon goes to 4 points and a backgammon to 6.

Once you doubled the stake and your opponent accepted, he has then the right of the doubling die. This means that he's now the only one allowed to make a new doubling request.

If he makes a new request and if you accept, the round will be worth quadruple and you again take the right back of the doubling die. In case you would like to request a third doubling, the value of the round could come to 8 points, and so on.

In theory, there is no limit in the number of doubling that can be requested, but having a round worth 16 points or more is quite rare.

Given that one can't refuse a doubling request made by the opponent, you aren't allowed to request it in any situation. For example in a game to 7 points, if your opponent is winning 6-5, you aren't allowed to request a doubling. Normally, in this situation, you would need a gammon, or two simple wins, in order to win the whole game. Doubling would remove that obligation and would allow you to win the game in a single simple win. Otherwise said, this would superficially remove the advantage your opponent had against you in the score.

More generally, as soon as doubling would allow to immediately win the game or remove such score advantages, it isn't allowed.

## Shortcut keys summary

- Enter: roll dice and move checkers
- To move a checker, press enter on the starting point and then press enter on the destination point
- To make a checker previously captured by the opponent re-enter the board, press enter on the destination point
- To remove a checker from the board, press enter on its point
- C: check the last dice roll
- I: obtain general game information
- S: announce scores
- T: see who's turn it is
- D: consult the value of the doubling die
- Shift+D: request doubling