X and O is a Tic-Tac-Toe game for the Nintendo Wii. It was programmed in C++ using devkitPro along with GRRLIB. It’s main purpose isn’t only for fun, but for letting others learn from the source. Every line is commented to help readers know what’s happening.

http://wiibrew.org/wiki/X_and_O(Learn_from_Code_Edition)