Answer:
I can be simple or I can be complex. I can be found in this riddle or in everyday life. I can be shapes or even colors.
I am a busy worker who is a water mammal.
As a state in the USA, I am round on both sides and high in the middle. What am I?
I am a bow that can never be tied or broken but can disappear. What am I?
The more I dry, the wetter I get. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.