Here are some notes that I wrote up awhile back about the double cube. If you see anything below that is wrong, or needs added - please let me know!

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Some random notes about double cube:

Good match point games would be 3, 5, 7, 9, 11, 15, 21


Scoring:

1) Winning a single game is worth 1 point.

2) IF you bear off all your men BEFORE your opponent has borne off any, then that is called a "gammon" and you score double points (2 points if cube is still on 1)

3) IF you bear off all your men and your opponent still has one or more men either on the bar or in your home area (6 places nearest where you bear off), then that is called a "backgammon" and you score triple points (3 points if cube is still on 1)

NOTE: As long as the person has borne off 1 man, even if now some of their pieces are on the bar - it is NOT considered a gammon or backgammon - since at least 1 piece had been borne off.



Double Cube: 1, 2, 4, 8, 16, 32, 64

1) Either player can decided to offer the first double (to 2 points) At that point the opponenet has the option to accept (bringing the game worth to 2 points, or decline - and forfeit the current game for 1 point. If they accept, then only the opponenet will have the option to re-double - bringing the game total worth up to 4 points, if their opponent accepts.

2) Double cube is NOT AN OPTION on the very first turn. So if a person wins the "roll off", they do not have the option to offer the double. The person who lost the roll off will then have first option to offer the double.

3) If a person is 1 point away from winning, there is NO POINT in asking them if they want to double - since 1 point will win the game for them. (IYT still asks if they want to double at this point and it annoys many many users!)

4) When the double cube reaches the point where it will win the game for a person, there is NO POINT in having the option of doubling anymore for the player. So if it is a 5 point match, and the cube jumps to 8, then there is no need to offer it anymore.



Crawford Round:

1) If either player reaches a score which is only 1 point away from winning the match, the next game is played as a Crawford Round. In a Crawford round, the double cube is NOT USED and the winner will only score the standard 1 point. Crawford Round only last for 1 game. After that 1 game, the double cube can then again be used for the rest of the match.



Other Things needed:

1) Need a way to resign game for MAXIMUM cube value without resigning the game (to help speed things up) So if I still have men on the bar and try to resign, it would be for 3 points. If I had not borne off any men and resign, it would be for 2 points. If I have at least borne off 1 man and resign, it would be worth 1 point. (values are for when cube is still on 1)

So possible when they try to resign a game, a "are you sure - this resign will cost you X points" should come up so they don't think they are resigning just 1 point when they may be resigning 2 or 3 points.


2) Need a way to resign COMPLETE MATCH


3) So basicly when the turn comes to a player, they will have the options to: Roll Dice, Double Cube, Resign game (for current max value), or Resign complete match. Plus I guess the current options of a draw of complete match would also be needed.

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Plus if you scroll back far enough, Alanback made a pretty good post about the subject, which I'll repost here:

A doubling cube is an object used to record the current value of a game that has been doubled one or more times. It's shaped like a die and has the numbers 2, 4, 8, 16, 32 and 64 on its six faces. A player who wishes to double the value of the game picks up the doubling cube before he rolls his dice, and offers it to his opponent with the side labelled 2 facing up. If the opponent accepts the double, he "owns" the cube and places it on his side of the board. The owner of the cube can choose to double at any later time when it is his turn, before he rolls the dice. He would offer it to his opponent with the "4" facing up. The original doubler then owns the cube, and can double again on his turn, and so on.

Here is an explanation of the doubling cube and of gammon and backgammon from Backgammon Galore!

I forgot to mention in an earlier post that multipoint matches would require the system to recognize gammon and backgammon as well.


Doubling
Backgammon is played for an agreed stake per point. Each game starts at one point. During the course of the game, a player who feels he has a sufficient advantage may propose doubling the stakes. He may do this only at the start of his own 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 one point. 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 number of points that were at stake prior to the redouble. Otherwise, he becomes the new owner of the cube and the game continues at twice the previous stakes. There is no limit to the number of redoubles in a game.



Gammons and Backgammons
At the end of the game, if the losing player has borne off at least one checker, he loses only the value showing on the doubling cube (one point, if there have been no doubles). However, if the loser has not borne off any of his checkers, he is gammoned and loses twice the value of the doubling cube. Or, worse, if the loser has not borne off any of his checkers and still has a checker on the bar or in the winner's home board, he is backgammoned and loses three times the value of the doubling cube.