Best riddles with simple answers

I sleep when you are awake, I am awake when you fall asleep. I can fly but no feathers to aid my flight. What am I?

Where does Valentine’s Day come after Easter?

It can fill a room without occupying space. What is that?

What can go up a chimney down but not down a chimney up?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth I am dissolved into air. What am I?

I am seen in the water if seen in the sky, I am in the rainbow, A jay's feather, And lapis lazuli.

I look flat, but I am deep, Hidden realms I shelter. Lives I take, but food I offer. At times I am beautiful. I can be calm, angry and turbulent. I have no heart, but offer pleasure as well as death. No man can own me, yet I encompass what all men must have.

When you put this in a heavy wooden box, the box will become lighter.

What can be swallowed, but can also swallow you?

If I drink something, then I am just over. However, I can eat anything. What Am I?