I liked the intro story :-P

Gameplay-wise i think the shotgun's reload time is too long for the spawn rate of the enemies. Also it'd be nice if there was some way to  'pick up' health (like shooting a health thingie or whatever :-P).

A fun take on the shooting gallery genre that made me forget it was a shooting gallery.  I was invested in making sure that the planet didn't get turned into a cigarette.  

I did come across a few issues though.  When there are two enemies on screen at once, I found it impossible to shoot both before taking damage.  The reload time on the gun and the time before the enemy hits you are the same.  To piggyback on that, I lost my all my health at the same time the boss showed up, and the game continued while my health decreased way below zero.  I was able to kill the boss this way.