The invisible border in level 5 was created, because in other case the player would have the possibility to finish this level too fast that I want.
I know that this solution is not a great one.Just as I as a game designer:)
I have changed the air control, by increasing the “air speed”. This is not a strong change, but I hope this will make the game experience better.
It is a good idea to give the player more air control. I will take note of it!
I think it would be much better, if you would change the background sprite. Otherwise it is good.