Rovio has teamed up with Apple to offer the popular Angry Birds Rio for free, as part of Apple's "App of the Week" promotion.

Making the app available for free is not only a rare occasion, but marks the very first time that Rovio is making one of its Angry Birds titles available absolutely free of charge.

If something could steal the spotlight from the surprise Temple Run 2 launch, it's definitely the Angry Birds giveaway. The free promotion is currently available for both the iPhone/ iPod Touch and the iPad versions of Angry Birds Rio, but it's just for a week. Normally, the game costs $0.99 for iPhone/ iPod Touch and $2.99 for the iPad.

Angry Birds Rio first launched in 2011 as a tie-in for the movie "Rio," but Rovio keeps updating it just as it does with all of its other iOS games. The latest update, issued in December, brought Angry Birds Rio to version 1.5 and added 24 new levels, as well as extra power-ups.

While Angry Birds Rio packs the same bird-throwing frenzy users are so accustomed to, it also brings a couple of new spices to the recipe. This iteration deviates a bit from the core series by letting users save animals from cages, rather than just crumbling everything down on top of the evil pigs.

Angry Birds Rio also sports boss fights, which marks a first for the Angry Birds series. The game also features more advanced graphics and the recently added power-up system aims to make things more interesting. In addition, the game now supports the widescreen of the iPhone 5 as well.

All games in Rovio's Angry Birds series have enjoyed tremendous success, and nearly everyone in the world has heard of Angry Birds. Angry Birds Rio makes no exception, which makes it all the more surprising to see the game available for free.

However, it's a limited time offer so hurry to the App Store to grab it while it's hot. If you still haven't tried your hand at Angry Birds Rio, now is the perfect time. Have fun!