Angry Birds has been one of the App Store's biggest and most visible successes, due to both the release's fun, easy-to-grasp gameplay, as well as Rovio Mobile's commitment to providing additional in-game content and new stand-alone games. The developer's winning formula has returned in Angry Birds Rio, along with a whole lot more birds.

For the uninitiated, Angry Birds is a physics-based game first released for the iPhone, and subsequently on numerous other platforms. Gamers are given control of a touchscreen-controlled slingshot used to send the eponymous avians careening toward stacks of various materials, with targets mixed in. The object is to use the birds allotted for each level to destroy the targets, gaining extra points for added destruction as well as completing the objective with birds to spare.

In the original Angry Birds, the targets are green pigs, but in this special promotional version of the game (made to tie in with the upcoming animated film, Rio), the swine are replaced with decidedly less angry caged birds that need freeing. This is nothing more than a cosmetic change, however, as the cages are destroyed and birds freed by simply smashing them - just like the green pigs.

Angry Birds is a stellar example of what a casual iPhone game should be, and Angry Birds Rio offers all of the great gameplay as the original. Users can look forward to killing time utilizing different birds' special abilities while working their way through the game's numerous stages, with gameplay that is accessible to small children, but still rewards strategic planning - an impressive combination.

Aside from the aforementioned cosmetic changes, the most noticeable difference between the original game and Angry Birds Rio is a noticeably lower difficulty level. While Angry Birds often required very precise bird-marksmanship, this promotional version of the game frequently lets gamers by with somewhat sloppier aiming.

The reason behind this decline in difficulty appears to be the way the levels are designed, with cages of birds spread throughout massive, rickety structures. Oftentimes, it only takes a single hit in a rather wide area to send the whole thing crashing to the ground, freeing all of the captive birds in the process. While plenty of kids enjoyed swiping their parents' iPhones to play the original game, presumably Angry Birds Rio was dumbed down a bit to further accommodate younger viewers of the upcoming film.

Angry Birds Rio's slightly easier gameplay does not break the game, but it certainly does make the levels fly by more quickly. Luckily, Rovio Mobile already has plans in place for additional content, with new levels set to debut in May, June, October and November of this year.

Aside from negligible aesthetic differences and less difficulty, however, Angry Birds Rio offers nothing new, which is the biggest problem with this release. Yes, Angry Birds was a huge hit, and there is no sense fixing something that is not broken. But to stay on top, Rovio Mobile is going to need to keep innovating, and bringing something new to the Angry Birds experience. Even something as simple as a new bird type, with an accompanying special ability, could have greatly enhanced the depth of Angry Birds Rio.

Angry Birds Rio is a great game, with what appears to be a significant amount of new content on the horizon. But for $0.99, gamers should expect something more than just the same old experience, especially when what they are buying is more or less an advertisement for a big budget film. If you are new to the Angry Birds phenomenon, then this release could be a great place to start, especially with its slightly toned down difficulty. But if you already have Angry Birds or Angry Birds Seasons on your iPhone, you will not be missing much if you skip this version.

Final Score: B-