How to play infinite tic tac toe
It's played on a normal 3×3 grid, and X goes first. Each player can only have three marks on the board. Once you have three, placing another makes your oldest mark vanish — in the game above, the mark that goes next is drawn faded. Three in a row wins. The board never fills, so there's no draw by a full board; we call it a draw after 80 moves.
You may know it as disappearing tic tac toe. Here it's called Fade mode, and it works on the bigger boards too: 4×4 and 5×5 keep five marks each, 6×6 keeps six.
The tip that wins
Unlike the classic game, this version isn't a draw: the first player can force a win, and the winning first move is an edge — not a corner or the centre. Before you count your threats, check which mark fades next: a two-in-a-row that includes it isn't a threat at all.
We solved the game by computer. The full story — the forced win, why the edge works, and how O should defend — is in our guide, Infinite tic tac toe: rules, strategy and the winning move.