The new Chess King 21 is considerably improved from the original Chess King or from any of the previous versions of Chess King. It is compatible with Windows 10 (or any previous version Windows) and IOS and has an updated GigaKing database with games till end of November of 2020, a full opening tree, and many playing modes. For analysis, it includes the Grandmaster engine Rybka with a rating of 2961 ELO and an automatic installer for the engine Stockfish with a rating above 3400 ELO