Everyone loves tic-tac-toe, but what about a 3D version of it? That's exactly what 3D Tic-Tac-Toe presents, taking the concept of a game invented years earlier and portraying it in video game form. The game can be played by yourself or against a friend, though if you choose the former, you can compete against a CPU opponent with eight difficulty levels. The game is played like traditional tic-tac-toe, but through four vertically stacked 4x4 grids. The goal is to stack four marks in a row, which can be quite the challenge compared to the original tic-tac-toe. 3D Tic-Tac-Toe also holds the honor of being written by programmer Carol Shaw, one of the industry's first female game designers.