Answer:
Just head and foot yet never tires of dancing.
Jack and Jill when up the hill jack fell down
They try to beat me, they try in vain. And when I win, I end the pain.
If you drop me I'm sure to crack. But give me a smile and I'll always smile back.
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.
Iām grown from darkness but shine with a pale light. Very round I am and always a lady's delight.