Why is Candy Crush Game so Addictive?

A friend told me - "Oh, so you haven't heard of Candy Crush game on Android yet? ..What world do you live in?" and out of sheer curiosity I installed the app and started playing it. Out of nowhere I realized that now I am at Level 137 and I still think about playing it when I am free. A lot of friends are talking about it and there have been numerous articles online that say why Candy Crush is so addictive. Interestingly, people should know that it was made to be this way. In an article in <a href="https://business.time.com/2013/11/15/candy-crush-saga-the-science-behind-our-addiction/" target="_blank" rel="noopener noreferrer">'Candy Crush': The Science Behind Our Addiction | TIME.com</a>, top reasons about the Candy Crush features are shared that make it so irrestible.

Here's asking fellow engineers - Why do you think are games as simple as Candy Crush so addictive?