Space Zap

Space Zap based purely on player reflexes. The goal is to defend a base anchored in the center of the screen from alien attackers that shoot from the four cardinal directions[2] There are four buttons, each corresponding to one of the attack directions. If a projectile ("mine") comes from the left, the player presses the left button, and so on. If the player fails to fire in time, the base explodes. After the player successfully defends the base they encounter an attack satellite that flies around the until the player hits it or satellite hits the base. The player starts out with three lives at the beginning of the game.

The game allows up to two players, taking turns. The cocktail table is the only machine to have two control schemes.[2]

The player receives points when they shoot a mine or, if lucky, hit the alien ship itself. The points values are 250 for shooting a mine, 500 for the ship, and 2,000 for the attack satellite. The player receives an extra base at the scores of 75,000, 150,000, and 300,000.[2][4]

Cosmic Ark, published by Imagic in 1982 for the Atari 2600, started out as a clone of Space Zap.[5] In the final game, the first part of each level is Space Zap played with an Atari joystick, but a second sequence was added to keep it from being repetitive.

Space Zap clones include Outpost (1981) for the Apple II, Colorzap (1982) for the TRS-80 Color Computer,[6] and Starship Pegasus (1984) for the Texas Instruments TI-99/4A.[7]