This is a cool game! I'd love to see it expanded upon!
Two things I think would really help it are a different background and sounds. Since this game takes place in space, you could have something like stars in the background. It doesn't make the most sense for stars to move quickly, but if your character is moving on a blank background and there are no other items on screen you don't have much of a sense of movement. For the first few seconds I wondered if my controls did anything.
Second is sound effects! You have good screen shake going on, but the most effective thing for game feel is audio. A nice sound when you shoot, destroy an enemy, eat an asteroid, and take damage yourself would make a ton of difference.
Awesome job!