🎲 Backgammon

Reading the board and making a move

You play purple, the CPU plays black, and a coin flip picks who rolls first each game. Your checkers travel right to left along the top, then left to right along the bottom. The six bottom-right points are your home board; the six top-right points are the CPU’s home, where your back checkers start.

You begin with the standard setup: 2 checkers on the 24-point (deep in enemy territory), 5 on the 13-point (top-left), 3 on the 8-point and 5 on the 6-point. That adds up to a pip count of 167, the total number of steps you need to bring everyone home and off.

Tap Roll, then tap one of your points; green dots mark every legal landing spot. Each die is a separate move, so a 6-1 can be one checker going 7 or two checkers going 6 and 1. Doubles give four moves. You can land on an empty point, your own point, or a lone enemy checker (a blot), which you hit to the bar, but never on a point the CPU holds with two or more.

Rules this version enforces, and the ones it skips

If you have a checker on the bar, tapping anywhere selects the bar first: you must re-enter before touching anything else. Entry uses the CPU’s home board, so a roll of 3 drops you onto the third point in from the top-right edge. If both dice land on blocked points, your turn is over.

Bearing off unlocks only when all 15 of your checkers sit in your home board. Select a checker and tap the OFF arrow on the right edge. An exact roll takes a checker off its point; a higher number can bear off from your highest occupied point when nothing sits above it. First to bear off all 15 wins.

• No doubling cube, and no gammon or backgammon bonuses: every game is one win or one loss on your W–L record.
• The first roll can be a double, unlike the tournament rule where both players roll one die each to start.
• You are not forced to play both dice or the larger die. Your turn ends when your dice are spent or nothing legal remains.
• Undo (the curved arrow) takes back only your most recent checker move, once.
• The restart button starts a fresh game without adding a loss. The board is saved after every checker move, but the dice are not: reload mid-turn and your checkers stay where you put them, then whoever’s turn it was rolls fresh dice.

Opening rolls worth memorising

These first rolls make a key point at once, so their best play is settled.

• 3-1: 8/5 and 6/5. You make your 5-point, the single most valuable point on the board.
• 4-2: 8/4 and 6/4. Makes your 4-point with no blots left behind.
• 6-1: 13/7 and 8/7. Makes your bar-point, the start of a wall against the CPU’s back checkers.
• 6-5: 24/13. Runs one back checker all the way to safety on your midpoint.
• A double, which this version allows on move one: 6-6 is 24/18 twice and 13/7 twice, grabbing both bar-points at once; 3-3 plays 8/5(2) and 6/3(2), making your 5- and 3-points.

The dice maths behind safe and risky blots

Every time you leave a blot, count how far it is from the nearest CPU checker that could reach it. Of the 36 possible rolls, a blot 1 pip away is hit by 11, at 2 pips by 12, 3 pips by 14, 4 by 15, 5 by 15 and 6 by 17. Past 6 it drops sharply: 7 or 8 pips is 6 rolls, 9 is 5, and 10 to 12 only 2 or 3.

So a blot 6 away is hit almost half the time, while one 8 away survives 5 times in 6. Leave exposed checkers out of direct range when you can. Entry odds work the same way: if the CPU has closed k of the six points in its home board, your bar checker fails to come in with probability k squared over 36. Against three closed points that is 9 in 36, a 25 percent chance of losing your whole turn.

Beating this CPU

The computer chooses its moves one die at a time. For each die it scores every legal move, then plays the best one. It rewards bearing checkers off and making points (two or more checkers together), and it penalises its own blots and its own checkers on the bar. It never plans both dice together or counts the race.

It also counts each of your blots as a plus for itself, so it is reluctant to hit you. That makes splitting and slotting cheaper than against a human. If you fall behind, an anchor (two checkers together) on its 4- or 5-point gives you a safe base while you wait for it to leave a blot.

Build blocks in front of its back checkers, aiming at your points 4 through 8. Six made points in a row (a prime) cannot be jumped at all.

When you are clearly ahead, break contact and spread checkers across your home points so every roll bears off efficiently. Eight checkers stacked on the 6-point waste rolls.

Four beginner mistakes

Most lost games come from a few fixable habits.

• Leaving both back checkers on the 24-point all game. Split them early.
• Playing the first die without checking the second. Since you are free to strand a die here, always picture both moves first.
• Bearing off without counting. Two checkers far back plus a big stack at home often loses a race you should win.
• Ignoring the pip count before deciding to race or hold.

A very old game

Backgammon belongs to the tables family, one of the oldest groups of board games still played. The Roman game tabula is a close relative. The modern doubling cube, which this version leaves out, was added in the twentieth century in American clubs.

Backgammon FAQ