The first mobile Fallout game has everyone coming out of their shelters.

Fallout Shelter, a mobile game about life in a post-apocalyptic world, is now the top downloaded free game on the App Store. Bethesda released the title at last week’s Electronic Entertainment Expo (E3), and it only took about two days for it to knock mobile game juggernaut Candy Crush out of its top-grossing spot in the United States. That growth continues — Bethesda announced today that Fallout Shelter is the No. 1 downloaded game in 48 countries, and the top downloaded app of any kind in 25 countries.

The first week since launch has been especially kind to Bethesda, with Fallout Shelter ranking in the top five top-grossing games in 37 countries. It has slipped a bit from its rank as the highest grossing game in the United States, but it still remains in the top 10. The company says that game play sessions have surpassed 70 million times a day globally.

An Android version is currently in development.

A new kind of monetization

Bethesda wants Fallout Shelter to show that monetization and in-app purchases can be fair and player-friendly, and this successful launch will help get the message out. Players don’t have to purchase anything at all to play and enjoy Fallout Shelter. The top-grossing rankings come solely from players purchasing items that they genuinely want to. Game director Todd Howard said in a statement that this rapid success shows that “gamers appreciate more depth and being treated fairly.”