How do you follow up a game like Monument Valley? One of the most iconic mobile games ever created, the beautiful puzzle game has been downloaded more than 15 million times to date. So when it came time to create a sequel, the team at Ustwo Games had an idea: they’d make it a surprise. After toiling away on the adventure for years, Monument Valley 2 was officially announced — and released — onstage at Apple’s WWDC this June. “Somehow we kept it a secret,” says studio head Dan Gray. “I have no idea how that happened.”

It’s still early for Monument Valley 2 — it’s been out for three months on iOS, and is debuting on Android today — but it’s looking like the gamble has paid off. And one big reason for that is that the sequel had a much more global debut than its predecessor. Both Monument Valley and its sequel were purchased more than 650,000 times in their first three months. But for Monument Valley 2, that number doubles when you factor in China, where the game has been available since launch. And while many mobile developers dramatically change their games to appeal to players in China, Monument Valley 2 was left largely the same, yet is still selling in big numbers.

“Day by day, we make more money in China now than we do in the US,” says Gray, “when everyone tells you paid games don’t work in China.” One of the reasons for the game’s success in China is due to the fact that, this time around, Ustwo partnered with tech giant Tencent for the release. In addition to the promotional opportunities that came from the partnership, Tencent also added social features to the game and an optional, localized version of the story.

“Your game needs to operate on a number of levels.”

Even though the game is off to a great early start, it’s unclear whether or not Ustwo will be able to replicate the long-tail success of the original Monument Valley, which was actually more successful in its second year than its first. Many of the reasons for that are things that are impossible to replicate. The original Monument Valley got a massive boost when it was featured in an episode of House of Cards, for instance, and more than half of its 15 million downloads came when Apple offered the game free for a week. Similarly, the studio also partnered with Apple for a charitable Project RED-exclusive expansion called “Ida’s Dream.” These moments helped the game reach the kinds of players who wouldn’t typically follow a WWDC keynote.

It’s not exactly easy to emulate that path when so many factors are out of your control. “The biggest thing is how you plan for not normal,” says Gray. For the studio, the plan became focusing on the areas they could control; namely, the game itself. Monument Valley 2 has a greater focus on storytelling, following the growing relationship between a mother and child, and it introduces a greater range of ways to interact with its beautiful levels. As Gray sees it, the only way to have a game as successful as Monument Valley is to appeal to all sides of the equation.

“Your game needs to operate on a number of levels — at least that’s how we work,” he says. “When we think about how kids interact with Monument Valley, they treat it like a toy. There are these amazing structures, and it’s very tactile, there’s a lot of audiovisual feedback. That’s the most simple form of interaction. And then there are the people who understand the basic premise. In Monument Valley 2, that is a mother and child trying to solve problems together. Then there are the people who talk on internet forums and Twitter, and have really high-level, deep discussion.”

“We have these other short stories that we’d love to come back to.”

Of course, the other way to keep momentum going is by adding more to the game; the original Monument Valley had one major expansion, “Forgotten Shores,” which led to a sharp increase in sales. Monument Valley 2 actually began life as a series of short stories, of which the mother and child was just one of several tales. So there’s no shortage of ideas when it comes to crafting additional levels for the sequel. “We have these other short stories that we’d love to come back to,” says Gray, though he admits that “it’s a hard thing to balance making a new game and continuing to support Monument Valley 2.”

Currently, a large portion of the studio is tinkering with prototypes, including some augmented reality experiments, in order to figure out what comes next. Though they’re not ready to announce anything yet, after so many years focused on impossible architecture, the team is ready to tackle something new. “We still get people going ‘Where’s Monument Valley 3?’” says Gray. “It’s like, ‘No, stop! We need to give you something you don’t know you want yet.’”