Chess Step Up uses the unmodified Stockfish.js 17.1 lite single-thread build by Nathan Rugg / Chess.com, based on Stockfish.
Licensed under GNU GPL version 3. See COPYING.txt in this directory.
Upstream source and build instructions: https://github.com/nmrugg/stockfish.js/tree/v17.1.0
Stockfish: https://stockfishchess.org/
Distribution: https://www.npmjs.com/package/stockfish/v/17.1.0
This build runs in a separate Web Worker. No engine code has been modified.
Corresponding source, build scripts and lite NNUE network: stockfish-17.1.0-lite-source.tar.gz (in this directory). Build instructions and upstream commit are included in DISTRIBUTION-NOTES.txt inside the archive.