"Clash of Clans" is a mobile game that was released for the iPhone in 2012. Since then, it has become the highest grossing game in the app store, grossing over an estimated $1.5 million a day, sparking headlines like, “A Clash Of Clans Addiction Nearly Sank The Royals' Season,” and “UFC Stars Hate How Much They’re Spending On Clash of Clans.”

Yet, the game is so profitable is not because the developer is tricking users out of their money (as in other mobile games). The revenue actually seems to stem from engaging gameplay.

Produced by Corey Protin