Notakto
Everybody plays X. Don't be the one who finishes a line.
First player's turn
How to play
Notakto is tic-tac-toe where both players play X. Take turns putting an X in any empty square, and whoever finishes a line of three — a row, a column or a diagonal — loses. There's no such thing as your line or theirs, so you're both trying not to be the one who completes it.
Nobody can draw. Six X's is the most a board can hold without making a line, so the seventh X always finishes one, and no game lasts past seven moves. Notakto is normally played on two or more boards at once. This is the single-board version.