Really great game! One of the better ones I've played. I really enjoyed the writing, and I really liked the attention to detail like how the dialogue would change after finishing missions and the tree helping you figure out what to do.
Some minor issues I had: it's not very clear when you're about to enter a zone. There's nothing really distinguishing them from any other pack of trees. I also didn't understand what the hedgedhog wanted: since he was saying the wind kept blowing the leaves away, I brought leaves on him, and because his dialogue changed to say "you're on the right track" I thought I needed to bring more on him at first.
Also, collecting warmth is fine at first, but it ends up feeling like busywork when you're done with everything else. Though this might be because of the bug I had: I couldn't glide even after helping the squirrel and getting an updrage from the lady bug, nothing would happen if I held space in the air (or on the ground, but I assumed it worked only in the air anyway)
I know this comment has been more negative than positive but they're mostly nitpicks, I really really liked your game and I feel like it's really close to being great. Good luck!