When as human vs computer - see below with game log.
Where did the rook and pawn come from?
When taking back a move to see what really happened and repeating the same move a different piece comes to life.
MacBook Pro 15″, macOS 12.1
You're welcome. I haven't played Chess on the Mac in awhile but there have been reports that the playing level may always be set at the highest level. That may have started with Catalina.
It seems you started the Crazyhouse variation.
Thank you. Regular is tough.. didn't know when I might have changed it to Crazy house..
Chess is having a bug and brings pieces from outside world
