Awesome pixel art, I especially like the player sprite, as well as the background. The music fit well, but I wish there were some sound affects. Right now the attacks don't feel very impactful.
Also it took me way to long to figure out that the player was on the left. Maybe an arrow above the players head would help out? I think I'm just stupid though. But after I went "Ohhhhhhhhhh, I'm the left dude" I was having a lot of fun.