Mobile casual gamers, rejoice: 2D Boy has delivered World of Goo for the iPhone and iPod touch! After a delay of almost two years, you can finally head to the App Store and pick up the wildly addictive, physics-powered puzzler. Eventually, World of Goo will sell for $2.99, but right now you can pick it up for the paltry sum of $0.99. It’s an absolute steal at that price, and definitely worth every penny.As is usually the case, the game isn’t available in all App Stores just yet. It’ll continue to roll out gradually across the globe, so keep your eyes peeled. For those of you with an iPhone 4 and its fancy Retina Display (or an iPad), you can also grab World of Goo HD as it’s now a universal app. It’s a bit pricier at $4.99, but worth the upgrade.In case you’re not familiar with World of Goo, the object of the game is to chain together blobs of goo (of course) and reach an exit pipe. It sounds simple enough, but real-world physics and precariously placed obstacles make it hair-pullingly frustrating at times. The lighthearted, cell-shaded graphics and cheery soundtrack make it easy enough to solider on through the game’s dozens of levels.Now all we’re waiting on is that mysterious “profanity pack.” Wonder if it’ll ever materialize…It’s 99 cents at iTunes.