The majority of the levels were short, many were impossible without a fire flower however.
Please don't overuse entities, try to stick to around 3-5 hostile mobs on a screen at once.
I found quite a few tiling issues in the levels, worldmap included.
The custom sprites didn't really fit into the SuperTux theme, either.
You're reading this? Yay!
What should I say? I don't know..