This is Ultimate Tic Tac toe, implemented using Node over Express, probably using websockets or something. I dunno, haven't really thought much about it yet.
This will be a two-player game. At least for now, I'm not planning on making an AI for this. That will take a lot more dedication than I can currently provide.
For the rules to this simply excellent game, check out this link.
There are some variants to this game as it works out. An exhaustive set of rules used by my implementation will be placed right here later, and also linked to in the app itself.