Hearthstone seems to be an unqualified success for Blizzard, receiving universal praise from critics and generating plenty of discussion in the CCG community. Its accessibility is complemented by a layer of Blizzard polish--you wouldn't even expect it was mostly ironed out by two people.

"We thought, boy these are super fun, but many of them are so complicated," executive producer Hamilton Chu told Kotaku. "Wouldn't it be great if we could make something that would let mass public to find the kind of fun."

Chu had worked with fellow Blizzard veteran Eric Dodds to create "Team 5," a small band of Blizzard developers working on the small project. But when other deadlines demanded attention, most of Team 5 was pulled off the quirky card game to help with Blizzard's bigger releases. Only Dodds and senior game designer Ben Brode were left to iterate on the idea. That gave them the freedom to iterate quickly, mostly using pen and paper to make their own versions of the cards. By the time Team 5 rejoined the pair, Hearthstone was essentially done. It was in a rough state, and running as a flash game, but the core mechanics were all in place.

"We pretty much pointed at the computer and said--'the game is done'," Dodds said. "Just remake that game over there."

Chu said the core game is extremely similar to the initial prototype, and that's thanks to giving Dodds and Brode the freedom to quickly experiment on their own. "The rate of iteration was like seriously, in order of magnitude, faster than in any game project I've ever been involved with," Chu said.