"Tic-tac-toe" or "Tris" is a paper-and-pencil game for two players, X and O, who take turns marking the spaces in a 3×3 grid. The player who succeeds in placing three respective marks in a horizontal, vertical, or diagonal row wins the game. When the grid is full and nobody has put in order the three marks, the game is draw.

GAME MODES:
The app has 2 game modes, and 4 difficulty levels:

1) Human-Vs-Human

- Multiplayer: players can challenge each other on the same device.

2) Human-Vs-Computer

- Easy: computer makes a lot of mistakes.
- Medium: computer makes some mistake.
- Hard: computer is stronger.
- Impossible: computer can't lose.