[Stellar]

It’s very simple. There are tools like Parse.com, GameAnalytics, Flurry and many more. They can track pretty much everything you do in the game. What button you click, for how long you’ve played, if you are a returning user and how many sessions you have played. They know type of your device no matter if it’s iPhone or Android. The can literally track every tap of your finger (it would not make much sense to do it but it is possible)

So if you wanna know more I would suggest you just go and check out what Parse and others offer to game developers.

The good is that Rovio has so many players that their statistics are really global. The bad is that they all use it to monetize their free games. But on the other hand you can’t expect developers to work for free. So they have to make money in order to make more games.

I know all that because I’m developer myself.