Rovio Entertainment, the company behind the hit mobile game Angry Birds, reportedly turned down a $2.25 billion acquisition offer earlier this year from Zynga, the San Francisco-based social gaming developer.

The claim, originally reported by The New York Times, is unconfirmed by Rovio, and Zynga cannot comment since the company is in its pre-IPO quiet period. Three people briefed on the situation said that Rovio walked away from discussions of a deal that would've given the start-up about $2.25 billion in cash and stock.

Zynga had reportedly tried to acquire another games company in July, but failed to do so. PopCap Games, the makers of Bejeweled and Plants vs. Zombies, turned down an acquisition offer worth $950 million, instead agreeing to be bought by rival Electronic Arts for $750 million in cash and stock, and an additional $550 million if they could meet specific earnings goals.

I expect a lot of game and tech companies will begin recruiting Zynga's talent after their equity becomes liquid, said Gabrielle Toledano, Electronic Arts' head of human resources. Competitors will make the case that they offer much more compelling opportunities for creative people.

Rovio had no incentive to take Zynga's money, as the company's CMO Peter Vesterbacka recently announced that Angry Birds has become the most downloaded game of all-time and fastest-growing game in history, scoring 500 million downloads in less than two years since its December 2009 release.

This is a fantastic landmark achievement for us, and we're extremely delighted to see such an incredible amount of people enjoying our games, said Rovio CEO Mikael Hed. We remain committed to creating more fun experiences and bringing exceptional quality to 'Angry Birds' fans everywhere.

The Finland-based company also said that Angry Birds is now the No. 1 game in 79 countries. Gamers worldwide play the game on Android and iOS devices for 300 million minutes daily, which amounts to a grand total of 200,000 years.

For those who have never played Angry Birds, the game is simple: players use a slingshot to launch multi-colored birds at structures populated by evil green pigs. Players must eliminate all of the pigs from each level before moving on. There are currently three different iterations of the game, including the original 'Angry Birds,' the holiday-themed 'Angry Birds Seasons,' and 'Angry Birds Rio,' which was released as a promotional tie-in with the 20th Century Fox animated film Rio.

But even with three games and countless levels and collectibles, people still want more Angry Birds. The company has been growing in size to accommodate the high demand, developing a long line of Angry Birds-themed toys, apparel, accessories, board games and a cookbook. Rovio recently announced that it will open up its first Angry Birds store in Helsinki and later open up shops in China, where the brand is huge - it's Rovio's second-largest and fastest-growing market --  but most of the available merchandise there is pirated.

We're insanely profitable, Vesterbacka said. We are very, very profitable. We're not a publicly traded company yet but we can fund our own growth.

The brand has grown so big that Rovio recruited former Marvel Studios chairman David Maisel, producer of the Iron Man films, to produce a feature-length Angry Birds movie.

Hollywood is hot for the brand, said Rovio's North American GM Andrew Stalbow. There's a very strong focus on Angry Birds to turn it into an entertainment franchise. That's why I joined.

Vesterbacka believes Rovio is not ready to file for an IPO tomorrow, but sees his company going public in maybe a year from now. Rovio most recently received $42 million in March, from investors including Accel Partners and Niklas Zennstrom's Atomico Ventures. Rovio CEO Mikael Hed said it's very possible the company would have another funding round before going public.

We're still building a lot of our infrastructure, our company, our platform, everything, Vesterbacka said. There's a lot of good discipline in having to be ready to go public.

Despite reports company employees are dissatisfied with Zynga, the company still hopes to go public by the end of the year. The company aims to raise $1 billion to achieve a valuation between $10 billion and $20 billion, and reportedly made $90.6 million in profit in 2010. Zynga's IPO was originally slated for earlier this year, but the company opted to delay its own IPO  in August.

Zynga has 60 million daily active users who spend two billion total minutes daily playing its various games, including titles like FarmVille, CityVille and Words with Friends. The company also boasts more than 269 million monthly active users on Facebook, the platform within which its earliest games achieved immense popularity.

Zynga employs approximately 2,500 employees worldwide.