I loved the characters and spritework! The dark part of the game looks, well, dark, but still super cute and pleasing to look at. I also thought having two different "sides" of the game, one where you collect lives and the other where you use them, is super smart! I'd love to see this more developed in the future.
I did have a lot of trouble with dark's fast movement speed, making precise platforming a bit difficult.
I was unable to get past that infamous spike jump, so I will rate fairly considering I didn't complete the game.