How Our Human-Like Chess Computer Works
How our chess computer learned to play like people from real rated games, how rated games are checked for cheating, common questions and how to contact us.
What Pawn&Queen is
Pawn&Queen is a free chess site with no ads. You can play a computer that plays like a person, play rated games online, solve puzzles, practise openings and endgames, and analyse your games with Stockfish, all in your browser or in the Android app.
The human-like computer
The named levels (Brand-new Robin up to Expert Jordan, about 2050) use a model fitted to rated games from the Lichess open database, a free public collection of rated games. The games are grouped by the players' Lichess rating, from under 700 to over 2000, and for each group the model learns what kind of move people of that strength choose: captures, checks, retreats, natural developing moves, and how often they miss something. In a game the computer looks at the moves a person of its level would consider and picks one by those learned chances. A few simple habits are added on top, so that it behaves like a person rather than a dice: it usually takes back what was just taken, notices a piece left hanging as often as people of its rating do, and plays more carefully in endings. That is the difference from the usual weak computer, which searches like a strong engine and then makes a random blunder now and then. Those computers play perfect chess and then give away their queen for no reason; ours plays believable moves for its level all game long. The ratings shown next to each level were measured by matches, not guessed. The levels above that are a classical search and then Stockfish, up to its full strength, for when you want the strongest opponent there is.
Fair play
Every rated online game is checked by Stockfish after it ends: each move after the opening is compared with the engine's choice. A game where a player matched the engine very often with almost no loss over many moves is shown to an administrator, who looks at the moves, the time spent on each and the time away from the page before deciding anything. Nothing punishes anyone automatically. Two players earn rating from at most three rated games against each other a day, which stops two accounts passing points back and forth.
Who runs it
Pawn&Queen is an independent chess site. It shows no ads and sells nothing, and what it keeps about you is set out in the privacy policy.
Is it really free?
Yes. Every feature is free, there are no ads and no paid plan, and you can play the computer, solve puzzles and analyse games without an account. An account (also free) adds rated online games, a game history, a puzzle rating and friends.
How does the human-like computer work?
Its levels up to about 2050 use a model fitted to rated games from the Lichess open database, grouped by the players' rating from under 700 to over 2000. For each position it weighs the moves a person of that strength tends to choose and picks one of them, so it makes the mistakes people of that strength make. It runs in your browser.
How is that different from a weakened engine?
Most chess computers play badly on purpose by searching like a strong engine and then throwing in a random blunder, so they play perfect moves and then hang a queen for no reason. Ours plays plausible moves for its level all game long: it misses the same tactics, likes the same natural-looking moves and gets careless the way people do.
How is Pawn&Queen different from Lichess or Chess.com?
Lichess is free with no ads too, and we like it. What we add is the computer that plays like a person, a computer that imitates 25 grandmasters, a style report that finds the grandmaster you play most like, and Gangster King, our own variant. Unlike Chess.com's free plan there is no limit on game reviews or puzzles and no ads.
What is Gangster King?
Our own chess variant: ordinary chess, except that both kings move like one other piece, and that piece changes every day. You can play it against the computer or in rated online games with its own rating.
How do you stop cheating?
Every rated game is checked by Stockfish after it ends, and games whose moves match the engine too closely are shown to an administrator, who looks at the moves and timing before doing anything. Two players can only earn rating from three games against each other a day. Nothing punishes anyone automatically.