I made a screen 0 chess game. I recall a couple of bugs, and since I' not an avid chess player, I punted on the project, and went on to other things. They were complicated bugs, not easily reproduced, I think just involving a couple of checkmate situations. Of course since I wasn't really playing it, there might have been more issues. I had asked TheBOB about designing chess pieces, and that's when his graphics chess project began. Sure not nearly as showy as my SCREEN 0 stuff, but what are you gonna do? I think I helped add piece movement, but TheBOB liked using CALL ABSOLUTE. I'm a CALL INTERRUPT guy! Come to think of it, the whole chess thing got started because Mac wanted some of us to hop on board (excuse the pun) with this Danish chess knock off, called Kriegspiel Referee. There is an entire sub-forum at QBF devoted to that project:
https://www.tapatalk.com/groups/qbasic/kriegspiel-referee-f188265/While I was contributing, I made my chess game. It was just easier to do the whole, than to just code my part in the project. More fun, too. Michael Calkins worked out the legal move part. The way I went about it for my game, was decidedly different than his method.
Anyway, good luck with the project. Now you'll have to beef up that mouse routine of yours a bit, with all the additional chess pieces this game will need. Why is that? Because you can play real chess with only a drag queen mouse routine!
Pete