Hearthstone is starting to rack up the digital sales for game publisher Activision Blizzard.

The company reported the results of the second quarter of its calendar year, which represents the three months ending June 30. In that period, the company generated $481 million in digital online revenue (non-generally accepted accounting practices). That’s up from $383 million compared to the same period in 2013, and the publisher attributes much of that success to its Hearthstone free-to-play collectible-card game. That game is finding a significant audience that is purchasing booster packs of cards as well as entries into a special Arena mode that can help them earn in-game items. This is Blizzard’s first game that uses the free-to-play business model, and it looks like a winner.

Blizzard’s big expansion to its action role-playing game Diablo III also contributed to the company’s digital revenue. The original game has now sold a total of 20 million copies, and a large portion of those players returned for Reaper of Souls content.

“Hearthstone has been exceeding all of our expectations,” Blizzard chief executive Mike Morhaime said during a conference call with investors. “We’re not ready to share a number, but we’re very excited about its future. Especially when you consider its expansion to other platforms.”

The success of these games have Activision raising its full-year guidance from $1.27 per share to $1.29 per share and from revenues of $4.675 billion to $4.7 billion.

Hearthstone is currently available on PC, Mac, and iPad. The developer is working on a version for iPhone as well as Android devices.

Hearthstone: Curse of Naxxramas - Extended Gameplay Footage