Addicted to sudoku

I spent so much time on solving sudoku puzzles these days. Its a good exercise for brains. Even though it's stimulating, it is definitely not a good idea to keep solving puzzles one after another, ignoring other work. How does addiction works? How can one get addicted to some simple things like playing sudoku?

State of mind

What could be the possible state of mind now? I mean the state of brain with all those indoleamines and catecholamines, are they balanced? I am wondering, as it is in its balance that each person feels good. Lack of seratonin(the feel good neurotransmitter) and indoleamine causes depression. Another aspect of the brain, how the primitive limbic system takes control of us and put us in a flight or fight situation even when we are just watching a horror movie amuses me. When information reaches thalamus, which is the sorter within the brain, the information is sent to the appropriate cortex area. But when the information has emotional content, amygdala bypasses the thalamus and takes control of the flow from reticular activating system and puts the person in the very emotional state as we see them to be in. This is one of the theories that I have come across today. It is pretty interesting.