Yars' Revenge

The player controls an insect-like creature called a Yar who must nibble or shoot through a barrier in order to fire his Zorlon Cannon into the breach. The objective is to destroy the evil Qotile, which exists on the other side of the barrier. The Qotile can attack the Yar, even if the barrier is undamaged, by turning into the Swirl and shooting across the screen. In early levels the player is warned before the Swirl is fired, and can retreat to a safe distance to dodge the attack. (wiki)