Hmm, I feel like I am fighting myself more than the enemies. The bullets don't fire very rapidly and they don't do very much damage (at least before you start upgrading). It feels very lethargic early on and, though that may be intended, it is too much so in my opinion. Secondly, I am not even sure how I use the gold or what its for.
On the other hand though, you definitely put a lot into its presentation. THAT shows most certainly! I just think that some of the gameplay, at least early on, needs some polish. Right now I feel the player is too weak for its own good early.