Site updates

Every build of this site and what changed, newest first. This page is not linked from the game and is kept out of search engines.

Current build: 2026.11.14.001

• 2026.11.14.001Greg Wright14 Nov 2026

  The first build of the chess game. You can play the computer at ten strengths, from beginner to full strength, or a friend on one screen: click a piece to see where it can go (or type a move such as Nf3 or O-O), step back through the game, flip the board, undo, resign, copy the game as PGN, and see the name of the opening you have reached. Pawns that reach the last rank ask which piece to become. Everything is on the game page, with plain-English guidance, a table of what each strength is like and the rules in short on the help page.

  The rules are exact: the move generator reproduces the published move counts for the six standard test positions (about fifteen million positions checked), and castling, en passant, promotion, stalemate, too-few-pieces, threefold repetition and the fifty-move rule are all covered by tests. The computer was written for this site: a search that looks several moves ahead (level 10 examines millions of continuations a move, for up to six seconds) with a hand-tuned judgement of positions. It runs in a background worker so the page never freezes. Weaker levels think less deeply and have a deliberately blurred judgement, so they make human-looking mistakes. Measured against Stockfish held to chosen ratings, level 7 beat it at 1800, level 9 at 2400, and level 10 beat it at 2400 and 2800 when both had a fraction of a second a move (see /help for the caveats).

  The opening book and opening names come from the Lichess chess-openings data set (about 3,900 named lines, public domain), turned into the book by scripts/build-book.ts. The pieces are drawn for this site. The board works with a keyboard alone (arrow keys, Enter, Escape) and with screen readers (every square is described and every move announced), and every colour pairing on the board is checked in light and dark mode. New or changed files: the game page, the help page and site updates.