Not so much difficult as it is mildly irritating. Some of the enemy placement is nice. I'm a fan of the retro graphics people have been cooking up lately but I have a small problem with the way these are presented. The sprites in this game move one pixel at a time, but your art work is stretched to a 3x3 pixel scale so the movement feels too smooth. The floaty jumping can also be a little frustrating. All in all though I like what you're doing here and would love to see more. Have you played La-mulan, Cave story, or tower of heaven? I think those'd be right up your alley.