This was fun! I really enjoyed the concept, the art, and the boss fights. The idea of splitting to get height was really creative, too; I don't think I've ever seen something like that in a game before. If I had a bit of constructive criticism it would be that the movement feels a bit too slow; I think it would be really fun to try a sped up version.
All in all, good job, and congratulations on making a game in a week!