Answer:
What can be swallowed, but can swallow you?
Two little holes in the side of a hill. Just as you come to the cherry-red mill.
Voiceless it cries, Wingless flutters, Toothless bites, Mouthless mutters. What is it?
By Moon or by Sun, I shall be found. Yet I am undone, if there's no light around
Different lights do make me strange, thus into different sizes I will change.
What is so fragile that saying its name breaks it?
Difficult
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?