I LOVE this music. I was just going to ask you to please upload it to YouTube until your game page credits disappointed me.
Alas, this is still a fun game. The one issue I have is I seem to find it hard to keep track (of both where my character is in relation to the screen and where I'm shooting). Design wise this could be because the player is too small/camera too zoomed out, too many "effects" going on around me with me shooting and enemies, or maybe lack of an aim indicator. I'm not claiming to know the answer, just my thoughts.
Your Metafab integration seems solid, good job!
And of course, shooting upgrade systems are always fun!