eh, it's nothing too clever, really.
Tic Tac Toe is a classic game, that I actually rather enjoy playing during my lectures at university (although I should be working).
However, the AI in this game is actually seems to be focussed upon offence. It does use 'winning tactics', it doesn't seem to take any steps against the old fashioned 'middle-middle, lower right, lower left' formula.' (which can be adapted to be 'middle middle, upper right, lower right', or whatever 'side' may be free.)
It's sometimes called the 'pyramid' method. But the AI in this game doesn't seem to recognise it.
Other than that, a sterling effort. Eight stars.