AiChessPlaying rules and scoring
How AiChess separates Elo, exercises and timed challenges.
The server validates moves, turns, clocks and results. Legal moves follow chess.js, including castling, en passant and underpromotion. Threefold repetition and the fifty-move rule require the available draw claim; fivefold repetition and 75 moves are automatic. Checkmate takes precedence over an automatic draw.
Flag fall loses, except the implemented insufficient mating material cases: an opponent with a bare king, or globally insufficient material according to chess.js (for example king and bishop against king). This is not a FIDE arbiter for every possible blocked position. Disconnecting does not stop the clock.
Accounts start at 1400 for Standard 30+0, Rapid 10+0, Blitz 5+3 and Bullet 2+1. Elo changes only in rated games between distinct accounts with at least one move per side. Computer, guest and casual games do not change it. K=40 for the first 30 games per category, then K=20; minimum 100. This is AiChess Elo, not FIDE.
Challenges have separate scores: one scored run per mode each day, the same set for everyone, 100 points per correct answer. Reset is at 00:00 UTC, also displayed in local time. AiChess Sprint is a timed challenge, not a game rating.
Review is available only after a game ends. Do not use external help in rated games. Server validation of moves and scores cannot guarantee that external assistance was absent; accuracy alone is not proof of misconduct.