Tic-tac-toe classic

Do you really can play tic-tac-toe? Check it. 4 difficulty levels.

Tic-tac-toe (or Noughts and crosses, Xs and Os) is a logic game for two players, X and O, who take turns marking the spaces in a 3×3 grid. The first player is you. The second player is your android device. There are 4 difficulty levels in this game (easy, normal, hard, very hard). There is one way to win for level very hard and two ways for level hard. Find it :).

Game rules:

The player who succeeds in placing three respective marks in a horizontal, vertical, or diagonal row wins the game. If there is no more room on the board and neither player has obtained three in a row, the game is a tie.