Nice job! I like the graphics a lot and the audio sounds clean! I think it would be nice to have the jumps be a bit higher. It can feel weird when the jump is that low. Also, I personally prefer using the mouse to attack, since Shift is on my pinky which can feel weird when moving around. Last thing, the theme isn't really used inside the game, so maybe expand on the theme a bit more?
Anyway, overall a good submission and well done!