Temple Run 2, the follow-up app to the massively popular Temple Run, was released recently. In the four days since its launch, the app, only available on iOS currently, amassed 20 million downloads. Not only has it rocketed to the top of the Free Apps list, it has also shot up to number 2 on the Top Grossing list.

Temple Run 2 serves as another example that the free-to-play game model does work, though it doesn't transfer to every game. Comparing the download numbers, Angry Birds Space managed to get 10 million downloads in three days, though it was available on multiple platforms. Google Maps managed to get 10 million downloads in 48 hours.

Temple Run 2 managed to pull in six million of those downloads on day one alone. Temple Run 2 is set to come to Android this week, so it will be just a few days until we see if Android users will be downloading the game in the same quantities. It will also be interesting to see if Android users spend the same, or more, on in-app purchases.