The game's feel is good man. It's audio effects are very well done. The background music is good. The theme connection is pretty good. There's a bit of issue with the difficulty, if the player sticks to the top of the screen and keeps moving the sword i.e. you keep pressing space all the skulls get crush. I think that's why you added the coins to disappear after certain periods of time. A timer with health decrease when on the side would add to the difficulty.
But overall it's really good. I would love to see more levels with obstacles and a fleshed out story. Keep working on this mate. Well done. Love it.