Not bad
Not a bad game, not amazing either. You could add more elements to it (such as powerups, different enemies etc.), faster spawning enemies and backgrounds, but other than that it was well done!
Oh, and once you have died, you have to click submit to go back to the main menu- it would be better if you had the choice to be able to go straight back to the menu without submitting your score.
You should make a sequel. Keep it up!