Click a gray square to set the value. Takes turns between circles and crosses. Displays winner when game is over, or draw if no one can win.
There is a separate list for each way to win: 3 rows, 3 cols, and 2 diagonals. When each sprite is clicked, it updates each list it belongs to with the value that was selected. So to check for a win, all you have to do is check whether any of the lists contains all of the same value.
