Licenses

Stockfish (chess dojo engine)

The chess dojo uses Stockfish.js 19.0.0 (lite, single-threaded), a WebAssembly build of the Stockfish chess engine, without modification. Stockfish.js is distributed under the GNU General Public License v3 (GPLv3).

• Full license text: Copying.txt
• Source code of the files distributed here: Stockfish.js v19.0.0 (Stockfish)

Stockfish runs in your browser as a separate program and talks to this site's interface over the standard UCI protocol.

Chess endgame puzzles

Positions and solutions of the chess endgame puzzles: Lichess puzzle database (CC0, database.lichess.org). The check that only one move works, and the reasons the other moves fail, were added by this site using Stockfish.

Chess piece images

Piece images by Colin M.L. Burnett (Cburnett), from Wikimedia Commons, used under the 3-clause BSD license. Copyright (c) Colin M.L. Burnett. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the copyright notice, this list of conditions and the following disclaimer are retained. THIS ARTWORK IS PROVIDED "AS IS" WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES.

Fonts

Dela Gothic One, BIZ UDPGothic and Martian Mono (all SIL Open Font License, served by Google Fonts).