It's not bad, man! It's a cool little game, especcialy for a first one!
The idea that you lose health when you shoot is very cool and makes the game very interesting. You could definitely panic when there are a lot of enemies on the screen and you're low on health.
Personally, while I think the shaking of the camera while shooting adds to the feel of the game, which is a good thing, it's a bit too much and can be distracting over time.
That being said, it's definitely a fun game and worth a try!
PS: It's funny how similar this game is to my game