Easy to grasp but quite difficult due to an extremely small margin of error. I managed to get to the third stage and have no idea how to deal with those pesky spitting flies :S
I'm kinda split on the artstyle, cause I think that most assets are fine by themselves, but they don't quite make a cohesive whole.
One small nitpick - the movement vector might not be normalized, cause the player character feels faster when moving diagonally then when moving sideways.