Good shit, reminds me of Vlambeer/Downwell crossed with Binding of Issac. Very readable and replayable.
I will say the camera's a bit too zoomed in to my liking, and it's hard to concentrate and dodge bullets effectively because of it. Also a shame I can't go back to the main "upgrade hall" if the upgrades behind the door I chose are way out of budget.
Still, if I were still in high school I could see myself cranking some rounds of this in the computer lab :)