Cosmic Commando is a 1st person shooter where you control a cross-hair on a single screen viewed from an elevated angle. Aliens appear one at a time from the back at the screen and move downwards in random patterns and you must blast a certain amount to move to the next level. If an alien reaches the bottom of the screen then it appears at the top again. You only have a limited amount of ammo which cannot be replenished and it is game over once you have run out of ammo. Each level also has to be completed before a bonus timer reaches zero and if it does reach zero then it is game over as well. Later levels sees another type of alien that attempts to remove ammo.