Short difficult what am I riddles for teens

I am the place where the earth meets the sky and the water kisses the land. I disappear twice a day, only to return again. What am I?

I have a headboard but no brain, and a footboard but no toes. You visit me to travel to worlds that don't exist. What am I?

What gets wet while it's drying?

I have more than 80 keys, but I cannot open any lock. What Am I?

I get whiter the dirtier I get. What am I?

I am something to make you think, I am something to make you know. I am something to which the answer you might never know. What am I?

When you have me more, you can see only less. What Am I?

I build up castles. I tear down mountains. I make some men blind, I help others to see. What am I?

My best buddy always makes mistakes. But I would easily get rid of the mistakes. What Am I?

I look taller when I am young. But as I get old, I become shorter and shorter. What Am I?