While Backflip Studios' previous App Store output tilts toward the casual end of the gaming spectrum (Paper Toss, Ragdoll Blaster), the developer's latest App Store release Boss Battles tackles a more hardcore genre -- the vertically scrolling shoot-'em-up.

Similar to the gameplay setup featured in Cave's Ketsui Death Label for the Nintendo DS, Boss Battles ditches the genre's typical stage-based progression and focuses instead on a series of boss encounters. While each of the game's eight bosses is easily beaten at first, players can challenge them again at higher difficulty levels for greater rewards.

Each defeated boss awards players a bounty of space gems, which can be used to purchase shields, helper pods, and weapon upgrades. Gems can also be bought outright via in-app purchase bundles, which range in price from $0.99 to $24.99. The freemium model is sort of an odd fit for a shooter, but it's difficult to argue with a features list that boasts both "an adorable but deadly raccoon," and "a Russian bear who thinks he's funny."