Cool game! I think it would look better if you used consistently only pixel art graphics or only high resolution graphics - and in case of pixel art, I recommend turning off interpolation. The controls are very precise and responsive so I didnt have much problems with any level. Actually, the thing that eventually stopped me was a bug - I felt under the ground and couldnt do anything. I think it happened after I jumped on this rounded corner of terrain instead of flat ground. Here is a screenshot. Don't forget to check out my game too!