Quad

Quad is a variation on Qubic/3-D Tic-Tac-Toe, spicing up ordinary noughts-and-crosses with an extra dimension. Two players take turns occupying squares with their chosen symbols, and each side attempts to achieve four in a row - in any dimension of the 4x4x4 grid. Either player may be human or computer-controlled (it's possible to let two machine opponents match wits against each other); the computer's skill level is freely adjustable, even in mid-game.