Think you've got Tic-Tac-Toe all figured out? ... Try Torus-Tic-Tac-Toe!
Glue each pair of opposite sides together, as shown to the left. Now there are more ways to get three in a row! (and more ways to lose -- keep your eyes open!) X wins in this torus tic-tac-toe game.
If you have a Web browser that runs Java applications
(e.g. Netscape 3.0 or later), you can play Tic-Tac-Toe
and other games on a torus or a Klein bottle at
Play a few games of tic-tac-toe on a torus:
Now try it on a Klein bottle. This is a bit trickier because of the flip.