chess

standard chess, every rule. play the computer on 50 levels, a friend online (make a room, send the link), or pass one device back and forth. click a piece then a square, or drag it. beat a level to put it on the board.

pieces by Colin M.L. Burnett, CC BY-SA 3.0. the computer is our own engine, levels and ratings are approx.

how to play chess

pick a mode: play the computer, play a friend online, or pass and play on one device. click or drag a piece and the dots show where it can go. all the normal rules are in: castling, en passant, promotion, draws by stalemate, repetition, the 50 move rule and not enough pieces.

against the computer, slide the level from 1 to 50. level 1 plays like a beginner of about 600 rating and makes the mistakes a beginner makes; level 50 plays like a strong club player of about 2000. the ratings in between go up evenly, about 29 a level. they are estimates, not measured ratings.

beat a level and your best goes on the leaderboard. a game where you took a move back doesn't count.

questions

how do i play a friend?
open play a friend, pick your colour and a clock (or no clock) and make a room. you get a 4-letter code and a link: send either to your friend. once they join, white moves first. you can offer a draw, resign, and ask for a rematch with the colours swapped.
what engine is it?
our own, written for this site in plain javascript. it searches ahead with alpha-beta and judges positions on material, where each piece stands, pawn structure, mobility and king safety. on the low levels it is held back on purpose: it looks less far ahead and sometimes picks a worse move.
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