Post-apocalyptic free-to-play iOS game Fallout Shelter is proving that engaging gameplay and treating your players like valued customers pays of huge dividends.

Developer Bethesda today revealed that the game, only just released, has pushed aside all other takers in the App Store, becoming the top downloaded game in 48 countries, and the top downloaded app (including games) in 25 more.

Looks like a fun, quality game that doesn’t trick you into buying in-app purchases can be successful after all.

“We play games on our phones all the time, and have always wanted to make one,” said game director Todd Howard in a statement. “To have our first mobile game be enjoyed by so many is stunning. It just shows that gamers appreciate more depth and being treated fairly. It also shows people love Fallout as much as we do.”

Fallout Shelter is the first foray by the triple-A gaming company, set in the same universe as its bigger cousin, Fallout, a series that has been around since 1997.

The mobile game allows you to build and populate an underground nuclear fallout shelter with variously talented characters who need to gather resources like electricity and water to survive for long. It’s incredibly engaging and has — in addition to becoming the top download — surpassed even free-to-play juggernaut Candy Crush Saga as a top grossing game.

Make sure you download this game, and if you like it, feel free to spend a bit to reward the developers for a delightful, quality, respectful game.