I survived with B rank! I was a little weary on it at first bc of the art but it's actually a pretty well designed game, well done!
My main gripes are that the gameplay feels clunky, too zoomed in, and the descriptions of the upgrades are vague (2x hp actually means 2x hp from enemies, not double your current health)
I would also recommend an ingame tutorial - do your best to instruct everything ingame.