Alien Stars is a scrolling vertical shooter. Players are cast in the role of a lone pilot who must shoot his way through swarms of enemy waves and boss ships over 11 stages. The player's ship can sustain a certain amount of damage, and is protected by both a shield and underlying armor when the shield is depleted. In order to improve firepower, three different colors of power-up can be collected which will improve the indicated type of weapon. Missile power-ups can be collected which will add to the player's ammunition for these secondary weapons. Other power-ups include Life, Shield, Battery restoration, armor restoration, double damage, missile strikes (which fire outward from the player), nuclear weapons and points.