Answer:
What I am filled, I can point the way. When I am empty. Nothing moves me. I have two skins. One without and one within.
What weaves webs as they grow?
You use it between your head and your toes, the more it works the thinner it grows.
Dies half its life. Lives the rest. Dances without music. Breathes without breath.
What is long and slim, works in light. Has but one eye, and an awful bite?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?