I would have liked some more narrative exploration beyond the fact that you are a skeleton so I don't think the game works very hard to adhere to the theme. Why are you a skeleton? Who are you fighting and why? Are you the bad guy or are they the bad guys?
I have a very old and slow computer so the speed was just right (I've seen the comments about the uncapped frame rate) but sometimes the controls felt unresponsive, with the character continuing to run, even though I wasn't pressing a key, or continuing to execute a move, which might be explained by the animation lock that someone else described but doesn't explain the running that sometimes got stuck. When it was working properly the controls were good and I was able to figure out a method for fighting the big enemies.
I really like the art and choice of restricted palette, as well as the animation of the sprites (and the parallax scrolling). Did you use an engine to make this game and, if so, what was it?