Beamrider

The objective is to destroy fifteen white flying saucers in each sector to complete it. You also need to destroy the sector sentinel for extra points. As you progress through the levels, even-numbered sectors will introduce new types of enemies that slow down your mission, but only the flying saucers need to be destroyed to advance.

You are armed with lasers and torpedoes, which are more powerful than lasers but have limited ammo. You can collect a Rejeuvinator to earn an extra life, but be careful not to shoot it, as it will turn into an enemy.