WWE SuperCard is running wild.

OK, maybe not wild, but the free-to-play digital card game is off to a nice start. SuperCard has surpassed 1.5 million downloads in its first week of release on the highly lucrative mobile market — a sector valued at an estimated $20 billion in 2014. It’s available for iOS and Android devices.

“In less than one week, WWE SuperCard broke 2K’s [existing download] records and became one of the company’s most popular free-to-play games to date,” said Chris Snyder, the vice president of marketing at 2K. “WWE SuperCard is a fun, engaging and addictive game for mobile game enthusiasts, WWE fans, and card collectors alike, bringing the larger-than-life action of WWE straight to their mobile devices to engage with at home or on-the-go.”

Of course, downloading SuperCard doesn’t cost you a penny, since it’s a free-to-play game. However, a large player base means companies have a larger pool of people that can potentially purchase microtransactions inside the game, which can lead to a healthy revenue stream.

However, despite the nice start, SuperCard still has ground to cover before it’s a mainstream success. It’s currently the 148th top free-to-play iPhone game on the iTunes App Store, so it still has a way to go before it’s a Clash of Clans (No. 12) or Kim Kardashian: Hollywood (No. 13) kind of success.

Still, according to 2K, SuperCard is already WWE’s most successful casual game, so this is some nice news for the professional wrestling company.