That was a very creative, silly and creepy rogue-like concept! Once I got the blood machine gun the game became very fun. The jazzy Girl From Ipanema-sounding song was a hilarious choice for the upgrade screen.
I managed to break out of the cycle after 5 attempts.
It was a little difficult for me to recognize the powers from the icons, and the fonts were very stylistic, but difficult to read. The number of bones on the upgrade screen was particularly difficult to read.
The boss was a little puzzling at first because it doesn't have as much feedback as the other enemies in the game. I didn't notice the health bar until my 3rd attempt because it was hidden in the darkness.
Nice work on the game, I'd definitely enjoy playing an expanded version with more bosses and more dangerous enemies.