Keys "s"=save "l"=load "b"=back once
A secret pawn carries the location of the king.
I programmed this so that pawns promote to queens, and did not allow castling. If a king appears on the square already occupied by the other, it is an automatic win.
Intrigue Chess by Nigel Chapman.
These are simple illustrations rather than strong opponents.
Bug reports? -- Thank you! Keep them coming!