Fallout Shelter was revealed at Bethesda’s E3 conference last week, and released the same day on iPhone and iPad. The app shot to number 1 on the top downloaded list in 25 countries, and overtook Candy Crush as the 3rd top-grossing app in the United States.

Fallout Shelter is a free-to-play sim game in which you play as the Overseer of a Vault. You begin with a small vault and just a few dwellers. You must manage their activities, as well as Vault resources and engineering. You level up your dwellers, expand your vault and watch everything grow, or collapse. It’s a really fun game that was well-received upon launch and perfectly befitting of the Fallout universe.

Bethesda showed off Fallout 4 at its E3 conference, which wowed audiences who had been waiting 7 years for a sequel to Fallout 3, but Fallout Shelter was a complete surprise. The game was announced and released on the same day, and it’s free-to-play, all of which made gamers very happy - which is reflected in its massive user base and play count.

The game can be found on iOS devices and will eventually make it to Android. For more on Fallout, stay tuned to GameSkinny.