The title screen from Space Strike.
In both games, the player controls a small mobile firing platform that he moves side to side along the bottom of the screen. Waves of aliens attack from above, sweeping back and forth and slowly descending. Barriers provide cover for the player, but are degraded by weapons fire both from above and from below. The level is complete when all the aliens are destroyed, but ends if the player gets shot or if the aliens descend to the point that they collide with the player.