Blizzard has put out many games over the course of its 20 year existence, but never one quite like Hearthstone: Heroes of Warcraft. At its core, Hearthstone is a collectible card game that revolves around turn-based, online matches between two opponents; players earn a set of basic cards, and can eventually obtain more advanced “Expert” cards by purchasing card packs with gold earned in-game, or with real money. Players can also “disenchant” unwanted cards, destroying them in exchange for arcane dust (a resource that can be used to create new cards).

On a cultural level it was certainly a challenge for Blizzard to bring its card game to market, as Blizzard has notoriously high expectations internally for the games it releases – and Hearthstone was no exception. “If you walk through our patio, in the middle of our buildings there’s a giant, 12-foot statue of an orc, and at the base of the orc is a bronze plate that says, ‘Dedicated to creating the most epic entertainment experiences…ever.’ We really think about that. With all of the games we’re doing, they need to deliver an epic entertainment experience. Historically, that meant something awesome and huge and with a ton of spectacle.”

“For this game, we knew we weren’t going to be able to make big environments with tons of characters,” continues Chayes. “Our approach instead was to re-imagine epic to really speak to craftsmanship. Could we make an incredibly physical game? When I’m interacting with the cards in the game, can they feel tangible? It was a challenge re-imagining epic so that it worked for a smaller team, and figuring out how we could hold true to what we think of when we think of a Blizzard game.”

The game has been in development for several years, and was initially intended as a PC release. It’s currently available on Mac, PC, and the iPad, and will be released on iOS phones and Android tablets and phones later this year. “When we first announced Hearthstone, not everyone knew what to make of it and we did get some raised eyebrows,” says Chayes. “This was about a year ago, when we announced the game at PAX East 2013; some people heard about it and were like, ‘Wow, that’s not what I would have expected from Blizzard.’” It seemed, perhaps, less epic than expected.

For the team, figuring out a new approach – where it didn’t have a massive team or lots of time to be able to deliver the game – meant a need to rethink what “epic” meant. A few months after the announcement, once Hearthstone made its way into people’s hands, players really got a sense of what was cool and different about it. “Almost universally, every time a new group of players came into the game, we heard, ‘Wow, that’s awesome. I never would have expected that I’d love this type of a game. But I’m super into it and I can’t wait to play more.’” It was a refrain the team heard throughout the beta, and the game’s accessibility has already brought some 10 million players into the Hearthstone fold.

“This is a game where in five minutes, you can get in and start playing,” says Chayes. “You don’t have to know anything about collectible card games, but you’ll be able to dive in and understand the rules of the game. You’ll see some really cool spells and minions you can play. It’s a new window into the Warcraft universe than what anyone has seen before.”

The choice to develop the game using Unity came fairly early on, and helped ease the challenge of bringing it to multiple platforms. “We made the decision that Unity was the right tech base, the right engine for us to bring the PC version of Hearthstone out to the world,” says Chayes. Later into development, the surge in popularity of games on mobile devices caught Blizzard’s attention, on both a corporate and personal level. “A lot of the games we were playing on the team happened to be on tablets and other mobile devices, and we realized that Hearthstone could lend itself very well to this platform – both due to the touch interface working well for card interaction and also the shorter play sessions that run about 10 minutes at a time,” says Chayes. “For all of those reasons, we thought that it would be a good thing for us to experiment and see if we could make the transition to tablets. After we did that evaluation, we made the decision to bring the game [into] the mobile space, and the fact that we used Unity made that an easier transition.”

“In fact, one of the great benefits of using Unity was that we were able to make the transition over to the tablet version of the game relatively seamlessly,” Chayes continues. “The game worked great for that because you’re dragging cards around and you’re flipping pages in the collection manager. It was a natural fit for mobile devices, so that actually worked really well. But the tech base really allowed us to get the prototypes up and running very quickly – I think that really spoke to how well Unity really helped us out with the project.”

One of the team’s major goals was to have the mobile version of Hearthstone differ as little as possible from the PC original, to maintain parity in terms of the experience. “If you were coming to play on an iPad and you had historically played on a PC, we didn’t want you to have to re-learn a bunch of UI or understand new targeting mechanics to figure out which minions you want to hit with your spells,” says Chayes. That said, there are some subtle ways that the versions differ. There’s no notion of “right click” when you’re playing on iPad, for instance, so operations that were reliant on that had to be remapped in different ways. Same with tool tips; when you’re dragging your finger across the screen, there’s no hover equivalent. On mobile, if you touch and hold on a card, it will display the tool tip after a short time.

The team was small by Blizzard’s standards: about 15 people for a number of years. In terms of the folks tasked with bringing the game to mobile, that sits at around four or five. “One of the things that really made Unity a great solution for us, is that we really like to iterate here at Blizzard,” says Chayes. “That’s one of the things that’s been core to our game development process in the past: we spend a lot of time going over the mechanics, multiple times, and working on them to make sure they’re as polished and as awesome as they can be.”

Because Hearthstone was a smaller game and had a shorter development timeframe than some of its other titles, the Blizzard team didn’t have as much time to go through its traditional iteration cycles. “One of the great things about using Unity is the speed with which you can iterate allows us to learn things that are working and not working, very fast,” says Chayes. “The fact that you can run the editor and it shows the same thing players are going to see in the game – and then stop it and go and identify bugs or polish things you want to tweak – really helped us learn faster about some of the things we thought we could be improved.”

“Another thing that was really great about Unity was that it had native support for a lot of the tools that our artists like to use – Photoshop and Maya – and can read in their base file formats, without having to go through some conversion process, which also sped up our process.” He says that one of the tools the team got out of the Unity Asset Store was PlayMaker. “That’s something we’ve used in the game to create scripted events alongside our animation system. It was actually a big help in enabling our art team to independently make cool events in-game.”

Indeed, this was the team’s first experience with Unity, turning development at one of the world’s most successful developers into something of a learning experience. “One thing that’s been great for us is the amount of support we found, even for issues we didn’t anticipate, as we began development with Unity,” says Chayes. “It was really easy for us to jump online and find out that, ‘Oh hey, guess what? This problem we ran into, other people have already encountered it in the past. We don’t have to go and find the solution on our own because there’s this great network of support.’ That was another huge reason why we chose to go this direction, and it ended up really helping us time and time again. On the whole, I think the Unity community has been awesome.”

The success of the PC, Mac and iPad versions of the game have helped reassure the team that the game it’s creating very much works, at its core. “For us, being able to bring people who’ve never played this genre before into the fold and really getting excited about what a collectible card game could be, has been a hugely rewarding experience, and has really been our goal from the beginning,” says Chayes. “Because for a long time, we have felt this genre is super-fun, and that maybe that fun is buried a little too deep to be experienced by everyone that tries it. With Hearthstone, our goal has been to open it up to folks who normally don’t get into this kind of game.”

Change of Hearth

“When we started work on Hearthstone, even some people here internally were going, ‘I’ve seen people playing those games in the past. They’re really complicated and they’re not really my type of game – I’m way more into StarCraft or one of our other games. But that’s cool. We’ll see what you guys come up with,’” recalls Hearthstone: Heroes of Warcraft’s production director Jason Chayes. “We really took that as a challenge. It was then great, after we went through the beta process and release, to hear some of those same people saying, ‘Wow, this game is awesome! I had no idea that this was what you guys were building. It’s great! I love it!’ Our goal was to expose the fun of the genre to a broader audience, and we couldn’t be happier with the results we’re seeing.”

On the Move

Hearthstone: Heroes of Warcraft is the first mobile game Blizzard has ever created, and this brought with it challenges small and large. To point to one of the larger items, it had not implemented the Battle.net platform to work on mobile devices prior to this project. “We didn’t have an authentication flow where I could enter my credentials, and then provide a way to bind them to my card collection when we started,” says production director Jason Chayes. Never mind the matchmaking system, social features, or cross-platform compatibility. “These are all things that we had to implement for a whole new platform when we made the decision to bring Hearthstone over to mobile devices. There was definitely a lot of work there for our Battle.net and game teams, and was certainly a difficult technical challenge as well.”