Hearthstone is one of iPad’s highest-grossing apps in its soft-launch territories

It’s just a digital card game, but Hearthstone: Heroes of Warcraft is quickly turning into Blizzard’s money-printing machine.

The collectible-card battler finally debuted to the public on PC and Mac earlier this year. And then on April 2, Blizzard released the free-to-play Hearthstone for iPad in Canada, Australia, and New Zealand. The mobile version has quickly shot up the most-downloaded charts in those territories, and it’s also enabled analysts and industry observers to see if fans are spending money. Turns out that they definitely are.