Hey, as a fan of minesweeper and occasional enjoyer of chess, this was really interesting! And from that player perspective, for me, at least, the rules were immediately clear. What I didnt know at first was, that you could move the chess pieces. Usually minesweeper clues can't really move, so I only realized they were movable during my third stage.
If some players get confused in the beginning though, maybe adding a quick tutorial pop-up during start-up could be a good idea?