The game is very well put together, but I agree that trees shouldn't be on the edge of cliffs. I've tried to overcome them many times but it's just impossible.
YellowAfterLife:
Air doesn't get saved. It's not that important either. The scores get submitted in a straight session. If you refresh the page, your highscores cut off. The coin upgrade costs 100 cash per level. The highscores also count the amount of cash you spent. Timing issues are not my fault, the new flash player doesn't allow things to run in different windows/tabs.