The game is a simple two-player game played on a grid that is 3
squares by 3 squares.
Players alternate turns placing their marks (traditionally 'X' and
'O') into empty squares.
The first player to align three of their marks in a row
(horizontally, vertically, or diagonally) wins the game, whereupon
they traditionally draw a line through those three marks to indicate
the win.
If all 9 squares are filled and neither player has 3 in a row, the
game ends in a draw.
For the first game 'X' plays first. The next game 'O' will play
first. Each player alternately has the first move.