Pretty good, simple system, nice song fits it well and looks very nice. I played only to level 21 on my second try so I don't know if my picture is considering everything that the game has to offer. It is fun for a short time but gets repetitive pretty fast. the only problem I have with it is, it is so very simple that is is basically too simple easy. run to a corner with only one entry and you won the round. Go deeper rinse and repeat. The spiked heart seems pretty useless and hurts more than it helps.
By the way if you throw away hearts before opening a chest you can get more than the basic cap for your heart ammo. That is an exploit but I actually found that funny so that is not a negative. That although adds to the "too easy" part.
All in all 4 Stars cool game for a short time, love to see it!