Backgammon

Backgammon is a race for two players, combining checker play with dice and, in match play, decisions about the doubling cube. Little Golem supports two formats:

Both formats support computer opponents and analysis of completed games.

Moving the checkers

Each player has fifteen checkers. From that player’s perspective, start with two on point 24, five on 13, three on 8 and five on 6, moving toward point 1. Each player rolls one die to start; ties are rerolled. The higher roller starts using both dice. Later turns use two dice; doubles allow four moves.

A checker can land on an empty point, a friendly point or a single opposing checker. A lone opposing checker is hit onto the bar and must re-enter before other checkers move. Two or more opposing checkers block a point. Use as many dice as legally possible. If only one unequal die can be used, use the higher one if possible. Bearing off starts only when all remaining checkers are in the home board. An oversized die can bear off only the checker furthest from the exit. The first player to bear off all checkers wins.

Match scoring and the doubling cube

In a seven-point match, an ordinary win scores one point, a gammon two (the loser has borne off none), and a backgammon three (also a losing checker on the bar or in the winner’s home board), multiplied by the doubling cube. Before rolling, a player may offer a double if the cube is centered or owned by that player. Acceptance doubles its value and gives ownership to the accepting player. Refusal loses the game at its previous value. Further doubles are disabled when the current cube already guarantees the match to either game’s winner. The first player to reach at least seven points wins the match.

Crawford rule

When either player first reaches six points, the next game is the Crawford game: doubling is forbidden for that game only. The cube returns in subsequent games. Each new game starts with a centered cube of value one. Little Golem does not use the Jacoby rule, beavers or automatic doubles.

Playing on Little Golem

Rolling and choosing the dice order

The opening roll is automatic. On later turns, the dice roll automatically when you have no legal doubling decision. If you can offer a double, choose between the cube and Roll, which appears on the board where the dice normally sit.

New rolls display the higher die first. Click or tap the dice to swap their order. Reopening the game preserves a roll that has already been made; it does not give you another roll or another opportunity to double before it.

Moving and sending a turn

1. Click or tap one of your checkers. It moves using the first available die in the displayed order, or the other die if the first cannot legally be used from that point. You do not need to select a destination.
2. Continue moving until you have used all the dice that can legally be played. Used dice fade. A double provides four moves.
3. Use Undo on the board to revise an unsent checker move.
4. Press the standard Send move button below the game to submit the completed turn.

You can also drag a checker to a legal destination. Enter checkers from the bar before moving any others; when bearing off, you can tap a checker or drag it to your Off tray. The interface enforces the requirement to use as many dice as possible, including the higher-die rule. If no checker can move, use Send move to submit the forced pass.

Moving checkers on the board prepares your turn; it does not send each individual checker move to your opponent. Rolling is recorded immediately.

Offering and responding to a double

In a 7-point match, click or tap the doubling cube before rolling to prepare a double, then press Send move. Use Cancel to discard an unsent cube decision.

When your opponent offers a double, choose on the board:

• Take: accept the new value and take ownership of the cube.
• Drop: concede the current game at the previous cube value.

Confirm either response with Send move. After a take, the player who offered the double resumes their turn and rolls; the accepting player does not immediately move.

The cube starts in the center. After an accepted double, it moves to the accepting player’s side, showing who may offer the next double. It is centered while an offer awaits a response. During the Crawford game it cannot be used. Single games do not display a doubling cube.

Playing against a bot

Little Golem offers five computer-opponent levels powered by GNU Backgammon for both formats. Sign in, open Robots, select Backgammon, choose the format and an opponent, then select Play.

The levels use different engine settings. The ratings shown on the opponent cards are their current Little Golem ratings, not fixed Elo promises for an engine level. Bots follow the same rules as human players, including cube decisions in a 7-point match.

Analysing a completed game

GNU Backgammon analysis is available for completed single games and completed 7-point matches. Allow time for processing after the game finishes. Open the completed game to see its evaluation panel, or use Learning → My analyses to find games whose analysis is ready. If the panel is hidden, leave the full-screen board view.

For an analysed decision, you can compare the move played with the engine’s recommended move and other alternatives. Match analysis also evaluates cube decisions: whether to roll or double, and whether to take or drop.

The evaluation uses match-winning chance (MWC): an estimated probability of winning. For a single game, this is the chance of winning that game; for a 7-point match, it includes the match score, cube and Crawford state. The graph shows player 1’s chance. Individual decision comparisons use the perspective of the player making that decision.

Decision loss is expressed in percentage points relative to the engine’s preferred choice in the same position, with the same dice. A change in the graph after a roll can also reflect the luck of the dice, so it should not automatically be read as a playing mistake.

The Analyse button opens a local board where you can explore moves. It does not request or start the server’s GNU Backgammon evaluation.

Rules reference: USBGF.