Yes, there's been a version of Minecraft available for Android devices since last year, but building towers in Creative mode can only go so far. Minecraft Pocket Edition 0.2.0 aims to fix that, enabling Survival mode on mobile devices for the first time. Along with the new game type — where you'll be able to build by day and cower from monsters by night — the update adds doors, fences, and gates to the available blocks, and includes an assortment of different tools. For those who do prefer Creative mode, you're not left out: flying has now been added. To top it all off, mobs are now a part of mobile Minecraft, with sheep and zombies the first creatures to be introduced. The app is available now in the Android Market for $6.99 (though the upgrade itself is free). As for iOS users, you won't have to wait too long to join in: according to Mojang's Daniel Kaplan, the update for the iPhone and iPad is ready to go and currently awaiting App Store approval.
Update: Sure enough, the Minecraft Pocket Edition 0.2.0 update for iOS is now live and ready for download on the iTunes App Store.