Answer:
As soft as silk, as white as milk, as bitter as gall, a thick green wall, and a green coat covers me all.
I'm the source of all emotion, but I'm caged in a white prison.
Upon me you can tread, though softly under cover. And I will take you places, that you have yet to discover. I'm high, and I'm low, though flat in the middle. And though a joy to the children, adults think of me little.
Give it food and it will live, give it water and it will die.
When liquid splashes me, none seeps through. When I am moved a lot, liquid I spew. When I am hit, color I change. And color, I come in quite a range. What I cover is very complex, and I am very easy to flex.
Break me and I am better immediately set and harder to be broken again.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?