This is an odd one..
I usually came around with games that have nice polish, but very shallow level design..
This one has it quite opposite, which is a favorable combination for me - the problem is though that the polish level is so tiny that it actually seem to hurt the game, i would recommend you to add some textures, doesn't need to be anything special, just search few minutes for a cute nether dirt texture and try to add a little bit more complex lighting, and it might up the game by for some people decently large margin, yet..