Xeno Defense is a defensive shooter in which all that stands between the survival of humanity and total extinction is your lone bunker which defends a small research outpost from invading waves of aliens. The player fights off aliens, gradually researching technology to allow improvements. These improvements include the construction of new weapons and new defensive structures, increasing repair efficiency, and various other effects.
Xeno Defense has 15 researchable technologies that unlock 10 weapons and 2 types of artillery strikes. 12 types of enemies assault the base, with only a few types coming in the first level and the rest gradually joining the fray in later levels as difficulty increases. Players wishing for more of a challenge can attempt to finish the game in a limited number of days.