The success enjoyed by the wildly popular digital card game “Hearthstone” was not apparent upon its inception. Despite a fervent launch, bolstered by the attached Warcraft brand, the game has had its share of growing pains, amplified by forging a path where there was none. But now that trail has led the game to a new, notable milestone: 100 million users.

Created in a lab by a small team within Blizzard Entertainment, the game is a phenomenon in a relatively niche genre, the product of forward thinking at the outset and balancing difficult decisions throughout a never ending process of revision and refinement. Now it stands as the presumptive king of digital cards, complete with a thriving esports circuit, and enjoys a massive audience at a time when other beloved card games are hoping to join the fray.

“[The ‘Hearthstone’ team] went through some challenging times when they were developing it,” Hearthstone senior VP and executive producer Chris Sigaty said, noting there was some question internally about the game’s development. “‘Is this really at the level of a Blizzard thing?’, initially, when they were making Hearthstone. And right from the moment I touched it, [I knew] this was gonna be brilliant and I was certainly gonna love it, and it turned out to be so.”

Development started on '”Hearthstone" in 2008 under the code name Project Pegasus, though it would be six years until its release in 2014. Former '”Hearthstone" production director Jason Chayes said the team focused on a few key tenets in those early years: charm and accessibility.

Played on a computer, tablet, or smartphone, “Hearthstone” players build decks around one of nine hero classes and battle in head-to-head card duels, trying to reduce their opponent’s life points to zero using minions and spells. Matches are short and intense, just brisk enough for coffee breaks or waiting on the laundry. The aesthetic of the game drives home the casual-competitive atmosphere, set in a fireside tavern amid mugs of ale and cheers from an off-screen audience.

Decks are filled using cards earned by playing the game’s many modes or buying packs, with either accrued in-game currency or real-world money. It’s that component that has made the game such a lucrative property for Blizzard, but also vulnerable to criticism from players who feel their investment, in terms of time, money or both, is not being properly rewarded.

The development team said Blizzard has worked throughout the years to make sure packs “feel like a good value.” Some features, like preventing players from finding duplicate legendary (the highest rarity) cards from a set in packs, are designed specifically to alleviate frustrations. Those features are unique to the digital space, fixing a problem experienced by anyone who has collected physical cards.

From the beginning the “Hearthstone” built the game with a digital-first mind-set, breaking from the limitations of traditional, tabletop card games. Corporeal titans like Magic The Gathering and the Pokémon trading card game were successful, but their digital versions tried to approximate the “real thing.” “Hearthstone” was made for screens, which allowed for certain freedoms.

“So when you're playing a ‘fireball’ card in a physical card game, that's usually when you extend the card to your opponent to see and say, ‘I deal five damage to your minion here or you as a hero,’” said Ben Thompson, creative director for the game. “And that's not near as compelling as playing the card and a gigantic five-damage or 10-damage fireball manifesting over the board, changing the lighting and swooping down for an explosive impact on your hero. That is something you only get to do in a digital space.”

The game’s simplicity and accessibility is another key factor cited in growing the game’s popularity. “Hearthstone” content creator and player Octavian “Kripparrian” Morosan believes the clear presentation was appealing to the game’s viewers.

“It's very easy to understand what's happening, where you are in any game, and it's very easy to develop your own opinion about the direction that the active player should take,” said Morosan. “It's just an extremely engaging game that's very easy to understand and watch, and that has a big impact on the different places of viewership, YouTube, Twitch.”

Twitch is home to hundreds of live streams, and “Hearthstone” has seen huge success on the platform broadcasting international tournaments and collegiate competitions. Twitch analytics site Sullygnome puts '”Hearthstone" seventh among gaming titles in average viewers on Twitch in the last year, with over 377 million hours viewed. (Note: Twitch is owned by Amazon, whose CEO, Jeffrey P. Bezos owns The Washington Post.)

Che Chou, franchise lead for “Hearthstone” esports, echoed the open and accessible refrain when asked how the game’s competitive circuit has helped the title develop its overall audience. As Chou puts it, “There’s no reason an 80-year-old can’t be playing an 18-year-old on the stage.”

“Hearthstone’s” path to 100 million users has not been without stumbles, though. Balancing a living game over the years gets more challenging with each new batch of cards players can use. Chayes specifically recalled one mechanic dubbed “Charge,” which lets minions attack when they’re played rather than waiting a turn, as a specific point of tension. Most minions have to wait a turn, to allow the other player time to react or prepare, but Charge lets the player let loose right away, a frustrating occurrence for those enduring the surprise attack.

One card, “Warsong Commander,” seemed strong but innocuous in the early days of “Hearthstone.” It’s an unassuming minion by itself, but it had a critical bit of text that gave other minions on the board Charge. Dropping powerful minions with huge numbers alongside the Commander let players get around the one-turn wait and go right for the kill.

The card text was adjusted to “whenever you summon a minion with three or less Attack, give it Charge,” but 2015’s expansion “Blackrock Mountain” saw the card rise up again, this time due to the prevalence of Grim Patron, a low-statistics minion that spawned a copy of itself every time it took damage and survived. Warrior players could summon a horde of Patrons using self-damage spells, give them Charge with the Commander, then slam the opponent for tons of damage. There was a predictable outcry from the community.

The team went back to the drawing board, producing “30 to 40” iterations before settling on the Commander as it is today: “Your Charge minions have +1 Attack.”

Even from the beginning, the team was dealing with different design choices that would require a lot of forethought, as new expansions could reveal more holes. The Priest class, for example, was going to be able to openly steal cards from the opponent’s deck, but the team soon realized that theft didn’t feel good for both players, and turned it into copying cards instead.

“They still have those cards, they still get to use them as they were planning to when they built that deck,” said Thompson. “But it doesn't completely undercut the next 10 minutes of their gameplay because you took a hinge point or pivotal card from [the opponent’s] deck, thereby neutering it.”

Since it’s a digital game, problems can be retroactively adjusted, though that’s a last-ditch option according to the team. Instead they try to iterate with new cards, and use a standardized format for decks to keep the competitive circuit level.

The team behind 'Hearthstone’ has also seen turnover. Game director Ben Brode had been the public face of the 'Hearthstone’ team, and his departure in April was a noticeable shift. But Sigaty said the change was not as stark as you might think.

“The reality of it is, there is no one person that defines a product here,” said Sigaty. “It's always the team that's doing it, and the team has made amazing sets and cards, and made great decisions about things in the absence of folks like Ben and [Hamilton Chu], and they will continue to do so, because it really is about the sum total of the team.”

Now that it has reached this new milestone “Hearthstone’s” position atop the card gaming community will be tested anew. More digital card games have been popping up, and even some industry titans are joining in. Wizards of the Coast just launched Magic The Gathering Arena, and Valve is releasing its Dota card game, Artifact, later this month.

But the ‘Hearthstone’ team seems to welcome the challenge.

“The way Blizzard makes games has never been from a perspective of being the first or the only game in the genre,” said Thompson. “I think that our intent has always been to be the best one we can make for a genre, and I think 'Hearthstone’ will continue to prove that out as we become part of an even bigger and bigger genre that we, thankfully, have had such a big part in creating, to the level it is today.”

Eric Van Allen is a freelance writer from Texas who covers games and esports.

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