Bethesda introduced its new iOS mobile game Fallout Shelter at E3 on Sunday and it’s already blowing up the Apple App Store, knocking King’s Candy Crush Saga out of its long-time No.3 spot in the top-grossing mobile games chart.

This is extremely impressive for a free-to-play game, especially since Candy Crush reportedly made $229.5 million in the first quarter. As of Thursday afternoon Fallout Shelter had over 16,000 ratings in the App Store, with an average of 4 stars.

The high level of interest is no doubt due to the power of E3 and it will be interesting to see if the game can hold its top position past the end of the conference today.

Similar to the desktop, Xbox and PlayStation Fallout franchise games, this one is set post-Apocalypse.

Gameplay is in a bunker, with players building new levels, attracting and keeping new Dwellers happy and protecting them from the dangers that lie outside. You can also play the game Sims-style by taking a more active role in their personal lives and training them to improve their abilities.

Fallout Shelter Protecting Dwellers is important in "Fallout Shelter." Photo: Bethesda Softworks LLC

The game is available to play on iPhone 5, iPad 3, iPad mini 2 or newer models and an Android version is in the works.

“We’re very pleased. Fallout Shelter is doing amazingly well, with no real buildup,” said Bethesda’s Pete Hines to GamesBeat during E3. “To take such a light approach to monetization compared to other free-to-play games — we felt like we wanted to err on the side of caution and make it very unobtrusive, make sure it was fun first and foremost. So far so good.”

Fallout 4 will be available for PC, PS4 and Xbox One on November 10.