Fallout Shelter, the terrific vault-building game from Bethesda, raked in a whopping $5.1 million during its first two weeks availability.

The payday is even more staggering when you take into account that the game is totally free to download and play, only offers one virtual add-on, and isn’t even available on Android yet.

Fallout Shelter was launched at E3 to promote Fallout 4, which is coming to consoles this November, and it’s exclusively available on iOS for now — though it has been promised for Android “later.” Despite being a relatively simple game, it’s hugely enjoyable and very addictive.

Fallout Shelter puts you in charge of your very own subterranean home from Vault-Tec. As Overseer, it’s you job to bring in more dwellers from the wasteland, and ensure they have the resources to live, and the skills they’ll need to be useful to the rest of the ever-expanding colony.

The game is totally free to play, and you don’t need to purchase anything to progress or have a good time. However, if you want to (and you will), you can buy lunch boxes that contain things like food, water, power, equipment, and rare dwellers with special skills.

These lunch boxes are the only in-app purchase available, and they can be purchased individually for $0.99, or in packs of 5, 15, and 40 for $3.99, $9.99, and $19.99 respectively. Despite being the only item available, Bethesda managed to make $5.1 million from lunch boxes in just two weeks.

This proves that with the right game, from the right name, the App Store can be a wonderful place. With money like this to be made, it makes you wonder why it took Nintendo so long to finally cave in to mobile.

• SourceVG247