Good.....but xtreme? Nah
Even though this looks very basic (yes I know its only tic tac toe :D ) but it plays quite nicely.
The only criticism is that the AI strength of play is very weak.
I found that you will always win if you defend on the computers turn to go 1st, and then on your turn to go 1st, you place an x in the top left square, then top right, then bottom right leaving you 2 options to get 3 in a row.
Other than that, well done