thanks for reporting that bug.

What I was going to say:
In the expiriment, please change e3=k to e3=i.
"k", according to the intro screen in the driver, means a king that hasn't moved, while "i" is a king that has. The expiriment is telling LegalMove that the king has not moved, in which case a castle would be legal, except for the fact that the king is in check.

Oh, wait... I see your point. There is no rook to castle with. I should make it so that it checks for a rook before checking for a check... That's an awfully good catch on your part.

Okay. The post refered to in the Status post has been updated. You can copy LegalMove% out of it, or make the change manually.

To make the change manually: In the LegalMove function, this is on line 39:

IF isthreatened%(0, sx, sy, dir) THEN why2 = 0: GOTO outnow

It needs to be moved 15 lines down, to between the "END SELECT" and "END IF". It will end up on line 53 (after it has been deleted from line 39).

Thanks a bunch for finding and reporting that bug. :-)
Regards,
Michael