Answer:
What can run but canβt walk?
We are all around, yet to us you are half blind. Sunlight makes us invisible, and difficult to find
The moon is my father. The sea is my mother. I have a million brothers. I die when I reach land.
By Moon or by Sun, I shall be found. Yet I am undone, if there's no light around.
I'm white, I'm round, but not always around. Sometimes you see me, sometimes you don't.
People take me on walks and I run and have fun. What am I?