3-D Tic-Tac-Toe

3-D Tic-Tac-Toe is, as the name implies, a 3D version of Tic-Tac-Toe. The object of the game is to place four X's or four O's in a horizontal, vertical, or diagonal row on the 4x4x4 board. There are nine games of which the first eight games are for one human player against the computer. The numbers 1-8 represent the skill level. Game 9 is a two player game. In the DOS version there are only two difficulty settings and no two player game. The Atari 8-bit version has an additional variation called Bottom-Up, which limits the player to only placing their X ot O on the bottom grid or only on a higher grid if an X or O is directly below it.