A little bit of chugging along got me pretty far until I slammed into level 22. Even after keeping the tab open for a month and coming back to it every few days I couldn't figure level 22 out. I finally cracked and looked at the walkthrough. Wow! There's pretty much no chance I would have cleared all the challenges in that level by myself. It's really a great level design. It reminded me of Jelly No Puzzle where it often appears there's no possible solution.