Notice that if you click on a square that is taken by the other player, the marker may turn into a question mark. This is because you have added both X-marker and O-marker classes to the document. If you used className instead of classList you would be able to take over another players square. Also, if you click on your own square you wasted your turn. Modify the event handler to check to see if there is a class on the element already. (Hint: this is a good use of className but there are other ways to do it.) Dont put a marker or count the turn if the square is already taken.