It uses the xboard/winboard chess-engine protocol to communicate.
Apart from 'regular' chess (also known as the Mad-Queen variant),
it can play Capablanca chess, gothic chess, knightmate, cylinder chess,
-berolina chess, superchess and courier chess.
+berolina chess, superchess, makruk (Thai chess) and courier chess.
Fairy-Max can be easily configured by the user to play other variants as well,
by modifying the ini file.
This ini file describes the rules of movement