Hearthstone is the most-downloaded iPad app in 16 regions — including the U.S.

Blizzard has never done mobile before — but this isn’t stopping its first game from dominating the charts.

The publisher’s online card battler Hearthstone: Heroes of Warcraft is the most-downloaded iPad game in the U.S. It also tops that charts in Brazil, Russia, Hong Kong, and 12 other countries, according to analytics-tracking firm App Annie. This rush to the top comes after less than 24 hours of availability. It previously launched on iPad in Canada, New Zealand, and Australia earlier this month before making its worldwide debut yesterday.

Hearthstone is free-to-play with in-app purchases. It has players putting together their own decks to face off against other gamers in head-to-head duels. It has quickly caught on with the gaming community after its release on PC and Mac earlier this year, but Blizzard designed it from the beginning to work as a mobile game. Make sure to check out our review to get our full, glowing thoughts.

Of course, since Hearthstone doesn’t cost anything to download, Blizzard is relying on its microtransactions, and it is already performing well in the category as well.

The game hasn’t ousted titles like Clash of Clans and Candy Crush Saga from the top-grossing iPad chart, but it is in the top five in two countries: Lithuania and Ecuador. Overall, it is a top 100-grossing app in 38 regions. It is the 17th highest-grossing piece of software on iPad in the U.S.

Hearthstone will need to collect a couple million more players before it can compete with the highest-performing mobile games.Still, this is a good start for the iPad-only Hearthstone. It will likely see another boost in performance when Blizzard releases it for iPhone and Android devices later this year. We’ll continue to track its performance as the title represents an important step in Blizzard’s transition into a mobile developer. The company has dominated retail PC games before going on to rake in million with its subscription-based World of Warcraft massively multiplayer title. Now, with Hearthstone, it aims to dominate the latest gaming business model.

In addition to Hearthstone, Blizzard is testing out Heroes of the Storm, which is its free-to-play multiplayer arena battler that is due out for PC later this year. That game will compete with massively successful titles like League of Legends, which made more than $500 million worldwide last year.