Keys "s"=save "l"=load "b"=back once
Philip Cohen, 1970. Pieces that move onto one of the center squares keep moving in the same direction. I did not allow en passant capturing of a pawn that has slipped. Otherwise, I did allow en passant capturing (the description in Pritchard's book seemed ambiguous.)
These are simple illustrations rather than strong opponents.
Bug reports? -- Thank you! Keep them coming!