It's been a wild ride for Mikael Hed. He founded Finland-based gaming company Rovio Entertainment five years ago and rode the astronimical success of the mobile game Angry Birds.

Today, however, is a different story. The company announced that Hed is stepping down as CEO, effective January 1, 2015.

Hed -- who will join Rovio's board of directors -- will be succeeded as CEO by former Nokia Corp. executive Pekka Rantala, who has served as Rovio's "chief commercial officer" since June.

Angry Birds became a global phenomenon after it launched in 2009, hitting the 1 billion download mark in a matter of months. Much of Rovio's revenues come from the licensing of the Angry Birds brand. Rovio says an animated Angry Birds film is slated for July 2016.

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Problem is, Rovio has struggled to transform its revenue model, making downloads free and charging users for in-game purchases. Rovio's other games, like Juice Cubes and Plunder Pirates, haven't seen similar success. And the company has faced stiff competition from other mobile game companies, like Candy Crush Saga maker King Digital Entertainment, which went public earlier this year.

The proof is in the numbers. After years of rapid growth, Rovio's full-year 2013 revenue was up only slightly to $216 million. Profits plummeted to $37 million -- less than half of what they were the previous year.

This isn't the first time a mobile gaming company has experienced a meteoric rise and then come crashing down.

Rovio's board of directors is hoping Rantala will have some more luck. At Nokia, he led some of the company's marketing activities as senior vice president. In all, he spent 14 years at Nokia in all types of marketing roles. More recently, Rantala served as CEO of Finnish food company Frazer.

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