I assume this is one of your first projects? Certainly is a good start, a couple simple improvements I'd suggest to make the game a lot better are:
- Making it clearer which powerup you get when you grab an item box
- Making enemy projectiles slower, currently it feels unfair to get shot and die because you can't easily avoid it
- Adding some kind of score either for number of enemies killed or time spent alive.
Hope you keep at it, good luck!