What a cool an interesting story/concept for the game! I found the art a dopey and charming, I think it would have lost it's appeal if it was too slick. Though if you stand right on the top right edge of the middle platform the arrows can't hurt you at all, and you win forever. Maybe an added element of wind knocking you off the concrete pillars if you stand on them too long. I really like the shrinking of the trees and running around dodging the arrows. I would have liked a little visual warning to show which hole in the wall they would shoot out from too.
Also maybe some kind of coin or collectible to pickup on top of the trees to keep the player moving and gaining points as well as trying to stay alive for time.
This was fun, with some additions it could be really great!