Sigma Chess

Sigma Chess is a freeware, master strength Macintosh chess program for Mac OS X. The feature set includes: Optional HIARCS engine, UCI Engine support, Databases, PGN/EPD, basic desktop publishing, endgame databases, novice levels, a true perspective 3D board, ExaChess compatibility and much more.

Sigma also runs on Classic Mac OS, but this is no longer officially supported.
Welcome to the Sigma Chess home page! If you own a Macintosh and you like chess, you should download Sigma Chess. You can:
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Play chess against the strong built-in engine: Adjust the playing strength to your own level simply by setting the ELO rating for Sigma Chess, and choose among the many playing modes, levels and styles.

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Play chess against the World Chess Championship strength HIARCS 13 and Deep Junior 12 engines bundled with Sigma Chess: Sigma Chess supports the UCI (Universal Chess Interface) protocol, so you can use other UCI chess engines for Mac OS X. Click here for a list.

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Analyze and annotate games: Instruct Sigma Chess to annotate games with its analysis, or add your own free text annotations including diagrams and move suffixes. You can even write and print your own chess literature.

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Maintain & access game collections/databases: The built-in database manager lets you filter and sort large game collections. Additionally you can import PGN game files that you have e.g. downloaded from the internet (see the Selected Chess Links). Sigma Chess can also be used as an engine from within ExaChess.
Customize the appearance & behavior of Sigma Chess: You can choose among the various piece sets, board types, types of move notation, colour schemes, the true perspective 3D board etc.