Just a question.Did anyone complete the game or it was too hard 

well that was different kept getting stuck on the 3 or 4th planet. Like how your weapon fire just sits there made a wall of blasts for fun.

Why do we have to kill the aliens? They're not hurting anyone.

Great setting! I really liked the creative gameover text and the movement with gravity was certainly unique.

Some feedback:

• Better collision: I got stuck on the pixels of the planets a few times. Bullets can also get the player stuck, so they shouldn't collide with it at all.
• Camera: damp it slightly to avoid the background moving around jerkily.
• Bullets: make them faster so they reach the UFOs before you.

Overall, good game. I hope you'll work on it more in the future!