Puzzles centered around tic-tac-toe (a.k.a. noughts and crosses).

Tic-tac-toe, or Noughts and crosses, is a paper-and-pencil game for two players, who take turns marking the spaces in a 3×3 grid with the symbol O or X respectively. The aim of the game is to place three of one's own marks in a horizontal, vertical, or diagonal row.

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