The object of Air Defense is to defend your land (at the bottom of the screen) from falling bombs. The bombs appear at various places at the top of the screen. As they fall, the player must line up the crosshair of his gunsight and fire when the bomb and crosshair are aligned.
Air Defense was written by T. L. Wahl and published as type-in source code in Compute! Issue 35, April 1983. Source code modifications for a wide variety of systems were provided.