I thought that the majority of the art looks good, there are some mismatches but nothing is perfect. I wish there was sound, would be nice to hear some feedback for the character. Enemies were overlapping in a way that made it sorta difficult to hit them, would be cool if they would collide with each other so they don't all stand in the same spot.
I think what you have is a great start, for example if the skeletons are coming in waves they could get stronger every time a certain number of waves is cleared. Maybe a weapon drop or dash skill would be able to help the character build up with the game.
I don't think it's bad, but it doesn't feel finished. I'd come back to play it when it's done :D
Great job and keep going, this is pretty sweet so far!