I really liked the graphics and the theme here. I found the platforming very difficult, however and I couldn't manage to beat the first level. I think that's ok if it's what you meant to do but it can quickly become frustrating. I don't have any easy answers as level design is hard, and I also make platformers that people sometimes say are too hard, but one thing I like to do is have the first non-tutorial segment be roughly 1/3 as hard as I can manage to pull off myself. Then gradually create segments or levels that are incrementally harder but save the "oh shit" jumps for the end (and realistically, nerf them too if you want anybody to finish it).