Phasor Zap is a game for the Apple II programmed by Chris Oberth and published in 1978 by The Elektrik Keyboard of Chicago, Illinois.
Enemy spacecraft appear from the edges of the screen and move straight across it, and it's up to the player to use to the paddles to focus four "phasor" beams onto each ship to destroy it, earning points.
When an enemy ship crosses either the vertical or horizontal center line of the screen, it fires, scoring a hit.
If the player hasn't already run out of phasor energy, the game will end when the enemies score 99 hits.
[1][2] The term "phasor" alludes to the phaser energy weapons used in the Star Trek science fiction series.