A free program for Android, by Pinkside.

Welcome to the world of Kuiper belt! In this world, you will be faced with the task of defending yourself from the incoming alien attack. The aliens will not stop until they have destroyed all of the humans. Luckily, you have the best weapons and armor at your disposal. Your main mission is to destroy the aliens and protect yourself from their attacks. You will have to face a lot of dangerous aliens and you will have to deal with them one by one. 

The game works offline, so you can play it anytime, anywhere!