Very good level design! And amount of content is impressive. I also liked that game tracks your progress and remembers enemies you killed, so you don't have to kill them again.
2 small things: the music wasn't looped, so once it finished there was no music for the rest of the game :( And another thing is that not every type of monster can continue level, so I had to die to re-select monster, that can. (Maybe that was a part of design hah :D )