I like the concept. I think you need you explanation below somewhere in the game. I normally hate tutorial pop ups but I think it would help this game because you are using a really familiar genre. I think when the player hops in they see that think, "Oh, I know how to play this!" But they don't.
Funny thing is, that with some cleaned up visuals and some more content, I'd certainly play this as a hack and slash game. It was more fun without the theme holding it back!