Learn backgammon
The rules, the strategy and a way to keep improving, and backgammon reference built from the engine's own numbers. Every figure on the reference pages comes from the same engine that analyses your matches, and each page says how its numbers were made and how precise they are, so you can judge them for yourself.
Articles
How to play backgammon
The complete rules: the board, moving, hitting, bearing off, gammons, the doubling cube and match play.
Backgammon strategy basics
The ideas that decide most games: counting the race, making points, when a blot is worth the risk, primes, anchors and timing.
How to get better at backgammon
Why your own matches are the best teacher you have, and a routine for learning from them with an engine.
Equity in backgammon
The number every analysis is written in: what equity means, how it is built from winning and gammon chances, and how the cube and the match score change it.
Backgammon error rates and PR
What a PR measures, which decisions it counts, what a good one is, and how much one match can tell you.
Accuracy versus PR
How HedgeHog's accuracy score is calculated, how it differs from eXtreme Gammon's PR, and why the two disagree about the same match.
Take points and the doubling window
Why a quarter of the games is the money take point, how the cube you receive and gammons move it, and how it is worked out at a match score.
How backgammon engines evaluate positions
What a neural network sees in a position, what 2-ply and 3-ply mean, how a rollout plays a position out, and how precise each answer is.
Rollout settings: speed, precision and pruning
How precise a short truncated rollout really is, why the first moves deserve a deeper search, how engines prune the plays they search, and the cache that makes it all affordable.
Move filters: how engines decide which plays to search
How GNU Backgammon's move filters and eXtreme Gammon's search interval pick the plays worth a deep search, why it depends on the network, and how far pruning can be pushed before it costs equity.
Reference
Opening moves
How to play each of the fifteen opening rolls, from full rollouts with the strongest HedgeHog network: the best play, the plays too close to separate from it, and their win and gammon chances.
Match equity table
Your chance of winning a match from any score, the post-Crawford values, and a calculator for the take point at any score and cube.
Position ID converter
Turn an XGID, a GNU Backgammon Position ID and Match ID or an OGID into the other two, with the board drawn so you can check it.
Race calculator
Pip counts, the Keith count and the 8-9-12 rule for any race, each with its double and take verdict, beside the engine's own answer.
The opening rolls
2-13-13-24-14-24-35-15-25-35-46-16-26-36-46-5
What the app itself does, how to read an analysis and what each setting changes are in Help, and the words backgammon players use are in the glossary. To see where your own play loses equity, analyse a match.