Keys "s"=save "l"=load "b"=back once
Units absorb the movement capabilities of units they capture. Royalty cannot cross squares under attack. Two-square pawn moves and castling only by unmoved units. Promote only if the move was one that the pawn component could make. The game is perhaps better in its progressive version.
These are simple illustrations rather than strong opponents.
Bug reports? -- Thank you! Keep them coming!