The following segment is lifted from http://www.joshuakennon.com/i-beat-cookie-clicker/ which wraps up the mental hooks cookie clicker hooks into.
This entire game is based largely upon a single mental model: The illusion of growth. It hijacks the neural system to provide a dopamine reward based on seeing the numbers escalate, and the reason it’s so appealing is Orteil has put a lot of thought into the mathematical relationships necessary to keep the next achievement just out of reach, while still feeling fair. This is worthy of a case study.