Answer:
I am whole but incomplete. I have no eyes, yet I see. You can see, and see right through me. My largest part is one fourth of what I once was.
Different lights do make me strange, thus into different sizes I will change.
If you break me, I do not stop working. If you touch me, I may be snared. If you lose me, nothing will matter.
Beautiful girls strut and sexy men 'do their little turn' on this.
What kind of pet always stays on the floor?
What covers its face with its hands, speaks no language, yet most known what it's saying?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?