Sigma Chess is one of the best free Mac chess games available to download. It has a true perspective 3D color chess board.

Instruct Sigma Chess to annotate games with its analysis, or add your own free text annotations including diagrams and move suffixes.

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.

You can choose among the various piece sets, board types, types of move notation, colour schemes, the true perspective 3D board etc.

Sigma Chess is a master strength Macintosh chess program for both OS X and Classic Mac OS.

Here are some key features of "Sigma Chess":

· 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.


Limitations:

· As mentioned on the main page, Sigma Chess 6.1 Lite is freeware. Although it's a complete, full strength chess program and not just a demo, certain high end features of the commercial Sigma Chess 6.1 Pro version are either limited or disabled:
· The new position and opening line filters are only available for collections with at most 100 games.
· The new player rating history graph only shows the first 10 games.
· Collections can contain a maximum of 1000 games.
· Changes to opening/position libraries cannot be saved.
· Only the KQKR and KBNK endgame databases are included. The commercial Pro version contains several other 4-piece endings.
· Automatic game annotation/analysis are disabled for collections.
· Diagrams are not printed when printing collections/online chess books.
· Diagrams are not included when exporting collections/online chess books to HTML
· Transposition tables are limited to 10 MB, whereas the commercial version can handle transposition tables up to a size of 320 MB.
· At most three windows can be opened simultaneously.
· Monitor mode is not available.
· UCI engines are limited to max 64 MB transposition/hash tables.
· UCI engines cannot reduce the playing strength to a specific ELO setting.
· UCI engines cannot access Nalimov tablebases.