Answer:
I can move even when you are still. I can be one or many.
Different lights do make me strange, thus into different sizes I will change
By Moon or by Sun, I shall be found. Yet I am undone, if there's no light around.
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. The wind is my lover, one-legged am I. Name me and see me at home in the sky.
Though easy to spot, when allowed to plume, It is hard to see, when held in a room.
I can only be played on a windy day
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?