This level has potential, but there are a few annoying design choices that bring the level down. First of all, even though it's barely visible behind the foreground leaves, the first Thwomp sprite-swap will catch most players off-guard since the level hasn't established that Thwomps are in the level prior to that point (or even established that the leaves are foreground images). I recommend lowering the Thwomp by one unit.
However the biggest problem in the level is this:
You shouldn't hide hazards behind foreground images because it's unintuitive for the player and he/she will take an unfair hit. Either remove the foreground images or remove all hazards behind them.
Also, you forgot to make the leaves in the last two screens of the level "Friendly."
Summary:
GOOD:
-Graphics aren't terrible.
-NPC placement compensates for flat block placement.
BAD:
--HIDDEN HAZARDS.
-Level is short.
-Music doesn't really fit the level that well, especially the lyrics (but you knew that already).
In conclusion: Like I said, this level has potential, but it also has its problems. The foreground leaves seem to be the source of all your level's problems, so if you remove those, change the song, and make the level longer (and add a checkpoint), I'm sure this would be pretty good. Until then, I'd say this deserves a 5/10.
