Cool beginnings of a game. I think there needs to be a bit more polish, such as when enemies are hit they explode into particles. You also need some kind of juicy sound effect. I'd also add camera shake for when you get hit or when an explosion occurs nearby. Also, adding some post-process effects like bloom, vignette and chromatic aberration, can make your game feel more polished and finished. These are all things that are cheap to implement as well.