We've been singing the praises of Hearthstone for some time now, a collectible card game based on the characters from Blizzard's World of Warcraft. It's the kind of refreshing experience that reminds you free-to-play games don't have to suck. So it's no surprise that over 20 million people have signed up to try it. Blizzard has been cautiously expanding the game, most recently adding some single player adventures and 30 new cards in an add-on called Curse of Naxxramas. Today our sister site Polygon reported that Hearthstone is planning it's first true expansion set, with more than 100 news cards.

Hearthstone, which currently has around 450 collectable cards, is far removed from the problems of titles like Magic The Gathering, which has to balance veterans with thousands, even tens of thousands of cards, against new players who are just starting out, a problem we discussed recently. It's still at a point where it takes a week or so to wrap you head around what's out there. Despite that Hearthstone has developed a healthy competitive scene, routinely among the most watched games on Twitch and with the beginnings of an international tournament scene. The goal now is to ensure that the game stays appealing to hardcore gamers and casual fans alike.

"We really want to pay attention to how that is for the entirety of the player base," says Hearthstone production director Jason Chayes, of the decision to add more than 100 new cards. "Does that feel like the right amount of content? Is it too little? Is it too much? We feel like this is a good starting point."