Play here: http://ken-soft.com/tictactoe/
Rules are very well explained here: http://mathwithbaddrawings.com/2013/06/16/ultimate-tic-tac-toe/
Note I did not expect so many people to actually read the code, I apologize in advance as I hacked it together pretty fast, Also ignore the non-functional AI for now, but feel free to add/redo any part you like. I will accept merge requests. Thanks. :)