Analyse

Guide

A trainer for getting better at backgammon. Play against a strong computer opponent and see how every move you make compares with the best, or set up any position and ask for the best moves.

Play a game

• Choose a money game or a match (1 to 25 points), and the bot: Friendly makes mistakes now and then, Advanced plays soundly without looking ahead, and Champion plays at full strength. Then press Start. You play the light checkers and move towards your home board, at the bottom right unless you choose the left (or a random side each game) under Your home board in Settings.
• The doubling cube: before you roll you can press Double. The bot takes (play on for twice as much) or passes (you win the game at the cube's value). It can double you too, before its roll: Take or Pass. Whoever takes owns the cube and is the only one who can double next.
• If you roll when you should have doubled, a note says so while you play your move. Every double, take and pass is graded like a move, and so are the close decisions not to double.
• In a match, the first game after either side gets to one point from winning is the Crawford game, with no doubling. A match is saved after each game, so you can carry it on later, on any device. Money games use the Jacoby rule: a gammon only counts double once the cube has been turned.
• Tap a checker, then tap where it goes. The places it can go light up in gold, and you can only make legal moves. Undo takes back the last checker you moved.
• When your move is complete, press Submit to play it, so you can try a move out first. A Double waits for Submit too (Undo goes back to rolling). Prefer moves to play straight away? Choose Play straight away in Settings.
• If you roll and can't move (or you're closed out on the bar), your turn is skipped and the bot plays on.
• Prefer dragging? Choose Drag to move in Settings. A checker can be dragged as far as your dice take it in one go (hitting on the way where it can; to miss a blot, move one die at a time), and dragged onto the tray at the side to bear off. A drop where it can't go slides back.
• When your move is complete it is graded straight away: a thumbs up for a perfect or good move, or a thumbs down with how much you lost and the top 3 moves.
• Press Bot's turn and the bot rolls and plays its best move (its last move is outlined). Then press Roll for your turn.
• Resigning: press Resign to concede the game. The bot judges what the position is worth: you lose a gammon if you were more likely than not to be gammoned (the same for a backgammon), otherwise a single game, times the cube. You see what you'd lose before you confirm. A resigned game is saved and rated like any other and counts in a match. The bot resigns too, before its roll, once it has less than a 1% chance of winning, at the result you're most likely to get (a gammon if you're more likely than not to win one). Accept ends the game there, or Play on to try for more: it then only offers again if what it would give changes. Start again is different: it throws the game away without saving or counting it.
• At the end, the game summary lists every move with its grade, and gives you an overall rating. Tap the next to one of your moves to see it on the board, with your move in gold and the best move in blue. For a slip, mistake or blunder, Why is the best move better? explains the difference in a few sentences (2p from your credit), from what the two moves leave: blots and the shots at them, points made, primes, anchors, builders, the opponent's board, and the win and gammon chances. Once contact is over, it explains the race and bearing off instead.
• Luck (turn on Luck in the game summary in Settings): each roll is compared with the average roll from the same position, in equity. The summary adds up both sides' luck and gives a verdict, such as Well deserved or Lucky win, and marks the luckiest and unluckiest rolls (0.15 or more either way). In a match, the match summary adds up the luck over every game, with a verdict once the match is over. Luck never changes your rating.

Analyse a position

• From a photo: press Upload a photo to pick one you have already taken, or on a phone Take a photo to use the camera, then drag the 4 corners of the outline onto the corners of the playing area, just inside the frame. Grab a corner anywhere near it, and a magnifier shows exactly where it is. Line the yellow lines up between the points (the straightened board underneath updates each time you let go), use Bar narrower / wider if the pink bar band is off, then press Read board.
• By hand: choose + Light, + Dark (or the photo's colours) or Remove, then tap points to add or take away checkers (tap the bar to put checkers on it). Start clockwise and Start anticlockwise set up a new game going that way round, and Clear empties the board.
• Drag to move (chosen in Settings): drag any checker between points and the bar. Drag one out of a tray at the side to add it, or into a tray to take it off.
• Set the dice, then press Best moves for every legal move, best first. Tap a move to see it on the board.
• Or press Cube decision (no dice needed): whether the side whose go it is should double and the other side take or pass, with what each choice costs. Set the game (money or a match and the score) and the cube first, as both change the answer, and the best moves too.
• Set Who's go, and press the corner where their home board is (where they bear off). The checkers stay where they are, and only the point numbers change.

Puzzles

• Each puzzle is a position with one clearly best answer: a move to play with the dice shown, or a cube decision. Every answer is checked by the engine. Some come from players' matches: those show the match score, and the answer is the best one at that score.
• Half come from a random theme. Once you've played a few games, the other half practise your weak spots: the themes from Your common errors that cost you most.
• The theme stays hidden until you answer, so it isn't a hint. Press Reveal theme if you want one.
• Puzzles have a difficulty from 1 to 3, at first from how easily a strong bot finds the answer, then from how often players get them right. You get a random mix of easy and hard ones from the start.
• Your first try at each puzzle scores 3 for the best answer, 1 for a close one and 0 otherwise. Your score is on Account. Solving puzzles is free, and Why? explains the answer for 2p.

Photo tips

• Take the photo from above, with the whole playing area in view and good light.
• The reader gets about 95% of points right, so always check the board before analysing. A message warns you if a colour doesn't add up to 15 checkers.
• Checkers not on the board or the bar are counted as borne off.
• Your photos: the straightened board is read by an AI model run on Amazon Web Services. A copy of your photo, the straightened board, what was read and the board you went on to analyse are kept privately on our server to help improve the photo reader. They're never shown to other players or shared. To have yours deleted, email contact@nihsko.com.

Move grades

Each move is graded by how much equity it loses compared with the best move. Equity is the average number of points you expect to win from the position (a win counts 1, a gammon 2 and a backgammon 3). Losing 0.04 costs about 4 points per 100 games.

Your rating

The game summary rates your play from your average equity lost per move. Forced moves (only one legal choice) don't count. For example, a game of 25 moves with 0.5 lost in total is an average of 0.020, which is Improver: about half a point per game given away against perfect play. The summary shows your average and total under the rating. In Account, the graph shows every game's average, with a dotted line for your average over the last 10 games, so you can see which way you're heading. Each level gets the same height on the graph, so one bad game doesn't squash the rest (games worse than Novice show as hollow points at the bottom); Show the real scale under the graph plots the equity lost itself.

Reading moves

• Moves are written from point to point, numbered 1 to 24 from your side (your home board is points 1 to 6): 13/8 6/5 moves one checker from 13 to 8 and one from 6 to 5.
• bar/22 enters from the bar, 6/off bears off, * means a hit, and (2) means the move is played twice.
• The bot's moves are written in its own point numbers, as players do in real games.
• Win is the chance of winning the game, and Gammon the chance of winning a gammon.

Use it as an app

Add Backgammon Coach to your phone's home screen and it opens full screen, like an app. On an iPhone, open it in Safari, tap Share, then Add to Home Screen. On Android, open it in Chrome, tap the menu ⋮, then Add to Home screen or Install app. Then open it from the new icon.

Good to know

• Whatever the bot's level, your moves and cube decisions are always judged at full strength, so your rating means the same against any of them.
• Cube decisions count towards your rating unless you leave them out with Leave out cube decisions under the graph in Account. Changing it re-rates every game.
• The summary is there until the next game starts. Each game's grades are kept in your account for the level graph.
• Your common errors in Account: after 5 games, your slips, mistakes and blunders over your last 30 games are grouped by what the best move did differently (such as hitting, making a key point or leaving fewer shots), with each theme's share of what they cost you. Coach summary turns these, and the Why? explanations you've read, into a few sentences on what to work on (3p from your credit).
• Add the page to your home screen to open it like an app.

Your account

• Sign up on the welcome page with a username (letters and numbers only) and your email address. Your password is emailed to you, and you can change it in Settings.
• Forgot username or password? under Log in: enter your username or your email, and a new password is emailed to the address on the account (up to 3 times a day).
• After 3 wrong passwords the account is locked for 5 minutes. A wrong password after that emails a new password to the account's email address, to keep the account safe.
• To change your email, or add one to an older account, use Update email in Settings. A link is sent to the new address, and it changes once you open the link.

Feedback

Feedback and ideas are welcome: email contact@nihsko.com.

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Game Summary