Angry Birds firm Rovio buys strategy game studio PlayRaven

HELSINKI (Reuters) - Rovio Entertainment , the maker of the "Angry Birds" mobile games and movie, said on Friday it had acquired Finnish game studio PlayRaven to expand into mobile strategy games.Rovio, which listed its shares last year, has been hit by tough competition and high dependency on the Angry Birds brand, first launched in 2009.It said it would now seek to develop a strategy game that would have nothing to do with the Angry Birds.Rovio spokesman Mikko Setala said the PlayRaven..