Angry Birds 2 hit 20 million downloads in the first week of its release, but gripes over an increased adoption of in-app purchases somewhat soured the news.

In a statement, Rovio Entertainment described the app as “the most downloaded game on both iOS and Android platforms virtually worldwide”.

“While Angry Birds 2 is off to a great start around the world, including key markets in the Americas and Europe, in China we are gaining a new foothold and seeing remarkable fruits of our well-functioning partnership with Kunlun,” said Alex Lambeek, the company’s Chief Commercial Officer.

Against the backdrop of strong downloads, a bout of negative reviews over a change in the way players collect lives were posted by some users.

Angry Birds 2, unlike its original predecessor, adopts a life-based mechanic similar to King’s popular Candy Crush, requiring players to either wait 30 minutes to play again, or complete an in-app transaction to buy more.

Rovio has previously used a number of monetisation methods, including a $0.99 up-front purchase cost.

Eric Seufert, vice president of user acquisition and network engagement, told The Wall Street Journal that there area a lot of places where smartphone penetration is now high, and 99 cents is “unaffordable”.

“The market has evolved. Free-to-play dominates mobile gaming and it dominates mobile. There’s likely not a future in the mobile ecosystem for paid games at the scale of Angry Birds,” he said.

The latest iteration of the popular game was dubbed the “first sequel” to the original Angry Birds which launched in 2009. There have been a number of spin-off games from the original title in the interim.