When playing 3D tic-tac-toe it is possible for the person going first to always win, simply by choosing the centre square as their first move. This is a radical departure from traditional two dimensional tic-tac-toe, where the game can always be brought to a draw but can never be won.

This can be easily proved with a simple mathematical proof - something that is very easy to show with pen and paper but rather more difficult to do with ASCII art.