Explore chess
How the chess on this site was built and checked
Not required reading. It is here because a school is buying care and attention, and this is the only sample of it available before a first session happens.
- 6 of 6standard test positions
- The board's rules are checked against perft, the published standard for chess move generation: it counts every legal position to a given depth from a known position and compares the total against published figures. All six standard test positions, at every depth, exactly right. Castling through an attacked square, en passant, promotion to a knight, all of it.
- 0 bytesof engine on arrival
- Stockfish is about seven megabytes. It starts downloading after your first move and never before, so every page is finished and usable before the engine exists at all.
- 44real positions
- Every tactical puzzle happened in a real game between real people. They come from the Lichess open database, published under Creative Commons CC0, and each one was replayed move by move before it went in.
- 1counting script, no cookies
- Visitor numbers come from Cloudflare Web Analytics, chosen because it sets no cookies and stores nothing that identifies anybody. There is no advertising pixel and no profile. It is also why this site still has no cookie banner.
- 100%playable by keyboard
- A whole game, from first move to checkmate, using only arrow keys and Enter. Every square announces its name and what is standing on it, and the last move is read out in normal notation.
- Drawnnot licensed
- The chess pieces on this site were drawn for it. So was the brain diagram and every illustration. There are no stock photographs standing in for a class, and no piece set licence to comply with.
Credits and licences
- Stockfish 18, free software under the GNU General Public License version 3, compiled to WebAssembly by nmrugg. It runs entirely in your browser and positions are never sent anywhere.
- chess.js, BSD licence, handles the rules. Its move generation is verified here against the standard perft figures.
- Lichess open puzzle database, Creative Commons CC0, is where every tactical position comes from.
- The chess pieces were drawn for this site, so no piece set licence applies.