What Is Tic Tac Toe? (cwoebker.com)

It's a visual representation of the most optimal tic-tac-toe strategy based on a given game state. Assume you're playing as X, who goes first. The largest X in the whole figure is in the top-left, indicating that that's X's optimal move. Now, let's say O decided to play in the top-middle square. You would "zoom in" on that ninth of the board; the black X and O represent the fact that this is the current state of the game. There is now a large red X in the middle, so that's where you should play your next move. Repeat until the game is over.