The jump and speed are completely unbalanced, so the challenge is to don't get out of bounds! I think the idea was completely different, but it still was a game.
I think level 2 > level 4 > level 1 > level 3, because you can just skip level 3 jumping it, but you have borders so you don't fall, different from level 1. On level 4 you have a city, and you need a perfect timing in level 2.