When you build software, sooner or later you’ll want to think about human behavior — most notably about what motivates humans.
I don’t mean Skinner boxes, points and ladders, variable reward schedules and the like as you might find them in “free to play but we have an in-game currency” games or in casinos.
Instead, I want you to think about human motivation in a sustainable manner that is also good for your users. Making them addicts isn’t the way.