Tic-tac-toe
You are X. Casual mode makes mistakes; Perfect mode has never lost a game in the history of mathematics.
Frequently asked questions
Can the perfect AI be beaten?
No. Tic-tac-toe is a solved game: with best play from both sides it always ends in a draw. The perfect mode plays the minimax-optimal move every turn, so a draw is your best possible result. Getting one every time is harder than it sounds.
What is the best opening move?
The center. It participates in four winning lines (both diagonals, middle row, middle column), more than any other square. Corners are next best with three lines each; edges are weakest with two.
How does the computer decide its moves?
Perfect mode searches the entire game tree with the minimax algorithm, assuming you also play perfectly, and prefers faster wins and slower losses. Casual mode plays the perfect move most of the time but sometimes picks randomly, which opens the door.