The two players in the paper and pencil game of tic-tac-toe alternately mark the spaces on a three-by-three grid with an X or an O. The winner is the player who successfully arranges three of their marks in a row that is either horizontal, vertical, or diagonal. Demo: https://codecanyon.net/item/tic-tac-toe-the-classic-flutter-tic-tac-toe-game/33790490 ...