Controls smooth enough. I enjoy the challenge of trying to shoot the enemies before they shoot me.
I would keep the weapon on Easy mode. It is useful for clearing the level of enemies, even if the enemies no longer shoot at the player.
Some of the jumps feel rather hard, even toward the beginning. I think the difficulty should climb a bit more gradually.
Music would be a nice addition. If you don't have the opportunity to team up with a composer, you can use attribution-only music, which is freely available for projects like these.