When the third season of House of Cards debuted on February 27th last year, it included a curious cameo: in one episode, newly-inaugurated president Frank Underwood was relaxing with an iPad, playing the gorgeous game Monument Valley. Two days later, the game had its second biggest money-making day to date, raking in close to $70,000 over the span of 24 hours, thanks to being featured in the show.

Underwood turned out to be a great pitch man, one of several reasons why Monument Valley was actually more successful in its second year of existence, compared to the first. According to developer Ustwo, the game has been downloaded more than 26 million times to date, and more than 23 million of those downloads came in the second year after it released. "We’ve actually had to spend a lot of time maintaining the game," says Dan Gray, head of studio at Ustwo Games, "and finding new opportunities for people to find out about it."

For the second year in a row, Ustwo has released a detailed infographic that showcases how well the game performed on various platforms. While year one showed that it was still possible for a premium game to make money on mobile, year two shows just how huge of an audience you can reach by offering your game for free — the biggest reason behind Monument Valley’s enduring success wasn’t a fictional US president, it was the lack of a price tag.

Nearly a year and a half after the initial release of Monument Valley, Ustwo partnered with Apple to offer the game — which usually costs $3.99 — for free for one week. Gray says that he expected, at best, to reach around a million new users via the promotion, but instead the game was downloaded more than 8 million times over the course of the week, greatly exceeding his expectations.

2015 also saw the launch of the game in China, as Ustwo partnered with publisher iDreamsky to adapt the game for that market. Again, this move saw the studio grappling with the concept of free. "The only way it was going to work, was if we made a free version of Monument Valley," Gray says. The problem was figuring out how to make the game work with that price point. Gray didn’t want to have ads in the game, or items that could be sold as in-app purchases, because he felt these would detract from the experience. "You want to escape for 20 minutes at a time and not be bombarded with an advert for a game," he says. The game ultimately utilized a structure that let players play the first few chapters for free, before paying to unlock additional parts of the game. Monument Valley has since been downloaded more than 11 million times in China.

"We want to create games that can impact everybody."

In fact, the vast majority of the game’s downloads have been free. Though it has reached 26.1 million users (not counting those who pirated the game), 21 million of those acquired the game without paying a cent. It might seem like a curious strategy for a premium game, where the upfront price accounts for the majority of the revenue. But Monument Valley also features a sizable expansion, called "Forgotten Shores," which can be purchased for an additional $1.99. "The hope was that a lot of people would download it for free," says Gray, "and then want to engage with it further and add the expansion on." One of the biggest complaints about Monument Valley has been its short length — you can complete the entire base experience in around an hour if you rush — but this in turn has made the expansion very popular. Gray says that around 35–40 percent of Monument players have purchased "Forgotten Shores."

That said, despite this success releasing the game for free, Gray says that the studio has no plans to make the shift to a free-to-play mentality, even if it would almost certainly be more profitable. "One of the things that we strive for, is we say that we want to create games that can impact everybody," he says. "I guess the key difference there is that lots of companies say ‘We want to make titles for everybody.’ But the key thing I say is ‘impact.’ There are a lot of free experiences that revolve around being a time sink, something mildly interesting to do whilst you’re waiting for the next train. We want to do the same thing, but be able to leave somebody with a lasting impression."

"If volume, and giving the average person those experiences is our goal, why don’t we go free all the time? The problem with that is that it really narrows the way in which you can design games. Games then suddenly become much more about the length of the experience, than the quality or the impact of the experience. It’s a really hard thing to balance."

Since the release of Monument Valley, a lot has happened at Ustwo. Last year the game studio released its first virtual reality game, Land’s End, on the Gear VR, and recently Ustwo Games separated from its digital design parent company (also called Ustwo). "We’ve gone from being a project team in a big company to being an independent entity," says Gray. The team has also grown; eight people developed Monument Valley, before eventually expanding to 15. The goal is to be able to work on two games simultaneously, without getting too big.

Even if it won’t be free, the studio’s next project, a currently unannounced game, will benefit from some of the other lessons learned from Monument Valley. While Ustwo has previously focused on creating games that are ideally suited for a particular platform — whether it’s mobile or VR — Gray is hoping to go in a different direction this time, in order to reach a wider audience. The plan is for a global release simultaneously on multiple platforms, including consoles and PC. But as for complaints that the studio’s games are too short, Gray isn’t too bothered about that.

"If the worst thing that people can say about your game is that they didn’t have enough of it, and it wasn’t long enough, then surely that’s the feeling you want to leave people with," he says. "You want to leave people wanting more, instead of being tired of the game that you’ve made."