I like the premise! I couldn't quite tell if enemies were firing at me or just doing damage when they hit the player character (though I suspect this one), because sometimes they could be right on top of the player sprite and there would be no change to the health and then all of a sudden I'm down 20HP and there's an explosion of sorts, without really having any change in where the enemies were in relation to the player. I also think it could have benefitted from some variety in the player's attacks, enemies after a certain point, or some variety in the level structure, as "shoot until you die" is not really my jam, so I did find myself getting a bit bored pretty quickly, even if that's my own personal bias coming in.