hey @ 0:30 the skelleton dies without beeing hit? @0:45 too!

as broozar said adding grass could add a lot to the overall feeling of emptyness.
movement seems a bit choppy from time to time and i didn't like the music voices. other than that its a good start.
you really should focus on good ai, movement and fightsystem bevore you continue to make more levels. or you might risk, that you have to rebuilt them after you got some ai going.
i would do that first then optimize the levels you already have and you got a nice starting point for more levels/enemies and so on...

is there some kind of story? or is it just running around killing everything you see?