Open-source credits.
The software and data behind these tools.
Stockfish 17.1
The analysis tools use the lite single-thread WebAssembly build distributed by the stockfish npm package, version 17.1.0, maintained in stockfish.js. The engine is distributed under the GNU General Public License, version 3.
Download the corresponding source archive, including build scripts. See the archive’s README for build instructions and neural-network downloads. The engine binaries are unmodified.
Puzzle data
240 positions selected from the Lichess open puzzle database, retrieved 9 October 2026. Its database exports are released under CC0. Source-game links, puzzle IDs, difficulty ratings and theme tags are retained. Our daily selection and instructional interface are independent of Lichess.
Chess libraries
Legal moves and notation use chess.js (BSD-2-Clause). The interactive board uses react-chessboard (MIT). Opening lesson explanations are original Chess Move Finder content.