Do jellyfish have brains?

Jellyfish are so weird, they look like they don't have blood or organs. I'm amazed by the way they look. Since they can calculate movement and react to the environment they must have a way to process information. Do they have brains?

Jellyfish are made up of over 95% water, and they do not have brains, hearts, gills, bones, or blood.
They have a complex network of nerves which respond to things, but they cannot think about things.

Jellyfish do not have a head either. They’re “radially symmetric,” meaning they’re organized around a central axis. They’re just as likely to meet a new environment coming from any direction in the sea. Jellyfish have a loose network called a “nerve net” throughout their bodies. When any part of the nerve net is stimulated, an impulse travels across it in all directions.