Basically like the normal version but the position in the small grid one person plays dictates which small grid the next player has to play in (if possible). So if you play in the lower left part of a small grid the next player has to play in the small grid in the lower left of the big grid - unless that is complete or already won. If you win a small grid your mark goes there and you're trying to win on the big grid by getting a line of small grids with your mark.
I was helping @InternetUser_005 with their version of the game and spotted some ways of doing it more simply. I couldn't resist actually creating the project once I'd spotted these options. I was reluctant to share if InternetUser_005 was still working on theirs but feel I've waited long enough.
