Unbeatable Tic Tac Toe

This Tic Tac Toe game features 4 modes: 

• 2 player (local)
• Easy (Computer places random moves)
• Medium (Computer plays like a human)
• Impossible (Plays with 99.99% accuracy)

(Of course, there is one specific case where you can beat the impossible level, cuz if it was truly impossible what's the fun in that? But it would probably take you some time to figure out the "bug")