Nicely done. Lovely art and animation. Great colors and detailed backgrounds. Lively music that doesn't get too repetitive. Good implementation of progressive increase in traversal abilities.
I could not quite get used to the wall-jumping mechanic (note, it never was one of my favorites). Also, the large enemies *looked* intimidating, but in practice were really not very aggressive. Lastly, pixel art doesn't really scale the same way that vector art or 3D objects do. So for some of the larger enemies, the difference in resolution can look a bit jarring.