Nice use of the theme. 

I like the gameplay, it's just that the scale mechanic doesn't really matter that much since the level takes care of that for you.

Felt like I missed some tutorials regarding the wall jumping and swimming.  Maybe I missed them?  And the vines felt very weird to control.  I felt like I couldn't get the right combination of keys down to stay on them when I wanted to be.

Neat group of mechanics, though!  I think there's room to expand upon them.  Felt a bit like early game Portal before you have the Portal Gun.  You could add a whole second part where the player has more control over their size changing and make a bunch more puzzles and stages around that.

Really nice feel... those vines are really weird though -- felt like it should maintain my momentum somehow.

I liked the variety of mechanics.