Hearthstone, Blizzard's popular digital collectible card game, pulls in about $20 million a month, split almost evenly between the PC and mobile versions of the game, according to analyst firm Superdata.

The information is detailed in the company's summary of its annual digital card games report.

How is Hearthstone suddenly dominating the digital collectible card game market? The analysts believe it's because the game has managed to recreate what World of Warcraft did to massively multiplayer online games in 2004. World of Warcraft delivered a more accessible take on the persistent online games and packed it with the Warcraft franchise's popular characters and settings. So too does Hearthstone, streamlining the sometimes convoluted rules of collectible card games and filling it out with colorful, popular characters and settings.

In a blog post, Superdata digs down into the dual successes of Hearthstone on PC and on mobile. The chart, seen above, shows that mobile jumped above PC in popularity with the release of the phone version of the game. As of early 2015, both were bringing in about $10 million a month.

It's worth noting that the sales figures included in the report and the blog post are estimates based on a number of predictors, algorithms and hard numbers. Superdata's Sam Barberie told Polygon that the numbers are pulled from credit card company sales and publisher's internal numbers. Those numbers are then built out with Superdata's own algorithms.

Berberie says the company routinely back checks it's numbers and have found that the margin of error is usually in the single digits.