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.

Moves are executed by entering a three-digit number representing the chosen square's coordinates (level, row and column). The basic game is augmented by additional features, like the ability to review previous moves, rotate the perspective along any axis, modify the order of play, or switch places with the opponent.