It's enthralled an entire generation and sold more than 100 million copies, so perhaps it should come as no surprise that for some hyper-skilled players, the open-ended, Lego-like building game Minecraft has become an actual, money-earning occupation. Just as the most-talented Lego architects earn a living showing off their blocky creations, there's good money to be made by anyone with the skills to craft Minecraft‘s cube-shaped digital blocks into beautiful sculptures and stunning worlds.

This March, Warner Bros used a slice of its $165 million Batman v Superman: Dawn of Justice marketing budget to hire several YouTube stars and a company called BlockWorksto create Minecraft renditions of both Gotham City and Metropolis – with the former including a Batmobile that players could drive around the virtual city. This was business as usual for BlockWorks, which is headed by Cambridge University architecture student James Delaney. The professional mapmakers previously built a Minecraft map of Tomorrowland for the Disney film of the same name, which likewise was played by popular YouTubers to the delight of hundreds of thousands of fans. They've also built worlds for Microsoft, The Guardian and the Royal Institute of British Architects, among many others.

It's been a meteoric rise for Delaney and his three co-founders. “I started playing Minecraft about four or five years ago,” says Delaney, who isn't scheduled to graduate from Cambridge until 2019. “I was just a regular school kid. I was interested in architecture, and it sort of grew from there.”

The four friends played just for fun. Then they noticed that Minecraft-focused YouTubers and the larger, more popular multiplayer servers were starting “to get a decent amount of payment” from donations – by 2013, many servers were pulling in tens of thousands of dollars every month.

Back then, these Minecraft-centric industries were just getting started, and in order to grow they needed a constant stream of new and interesting worlds to play with. Delaney sensed the opportunity. “We thought if we provide these guys with really good builds, there could be a business here,” he explains.

That was three years ago. Now that team of four has become 42, and BlockWorks is a legit business – albeit one for which the “office” is split between Skype and a private Minecraft server. Delaney is managing director, which sounds like it would be hard to juggle with his studies. But he has a handle on it. “The good thing about university is that you spend half the year on holiday,” he says.

BlockWorks' business is anchored by Minecraft‘s corporate owners, Microsoft, which reached out to Delaney and his team in June last year after nine of them published a 31,752,348-block map that depicted a futuristic civilization deep beneath the surface of the ocean. The tech giant has since commissioned BlockWorks on several projects, including the elaborate map that starred at this year's Microsoft's E3 briefing and a set of replicas of the seven wonders of the ancient world – the latter so that school kids could visit them in Minecraft: Education Edition.

When not building Minecraft maps for Microsoft or big-name brands and YouTube stars, the team at BlockWorks busy themselves with projects such as Ireland 2066 and Climate Hope City. These were both conceptual builds with an educational bent – Ireland 2066 was made to inspire school-aged children in conceiving their entries for a competition celebrating the past and future of Ireland, while Climate Hope City was a collaborative effort with fellow Minecraft professional creative Adam Clarke and The Guardian to envisage a fully-sustainable city using only existing green technologies. This sustainable city build ranks among Delaney's favorites. “They didn't give us a plan,” he says. “Just design and build a sustainable city, which is kind of an architectural student's dream.”

BlockWorks is the most prominent Minecraft “build team,” as they call themselves, but there are dozens of others. Most are led by teenagers or 20-somethings like Delaney – though at least one well-known professional mapmaker, Adam “Wizard Keen” Clarke, is over 40 – and the rewards run the gamut from pocket change to checks big enough to keep full-scale creative agencies in business. Delaney only knows of three or four build teams that operate at the upper end of the scale, however.

“You've got kids who might be really great at Minecraft,” he says. “They've been doing it for four years, but they're still just doing it for fun. Maybe occasionally they make a few hundred dollars from a server that wants to have a really nice looking spawn [starting area for players] from them. Then on the other side of the spectrum you've got people who are taking it incredibly seriously and they're working with some of the largest companies in the world – huge advertising budgets.”

“And so the scale of work in what is a relatively niche industry is absolutely enormous. I don't know if I can give any figures,” he continues. “But enough to make a profitable business.”

Take GoCreative, for example, which was founded by a German teenager and Brandon Relph, an enterprising 15 year-old from the UK. Relph made £10,000 last year building scene recreations from a film and scale replicas of famous landmarks – all the while maintaining good grades at school and setting aside only a few hours a night for hisMinecraft-centric business. GoCreative is now a small multinational company with around two dozen employees and commissions coming from the education and non-profit sectors as well as entertainment and tourism. In March, a charity that aims to combat declining honey bee populations hired them to help visualize the science in Minecraft. They created a model that depicts gun-toting ants assaulting a giant, peaceful beehive.

Another successful group, Everbloom Studios, has an origin story similar to BlockWorks'. Co-founder Matthew Banks parlayed his love of Lego and model making into a Minecraft addiction early in the game's life. He got good just as Minecraft was entering the stratosphere, and he and a few friends he'd met online started getting offered money to build maps for multiplayer servers. Their first paid project, published in February 2013, was a small Nordic-style seaside town where players could rest and recuperate before heading back out to battle against the wilderness. (It was also where their character would “spawn” on arrival to the server or respawn upon death.)

Fast forward to today and they have 40 members, 25 of which handle building (10 work on videos and the rest fill “niche roles”). Everbloom still gets “over 90 percent” of its work from servers. They build player hubs, starting areas, and maps for special mini-games. Popular mini-games include a Minecraft spin on laser tag or The Hunger Games, castle battles, boat races, Minecraft renditions of popular sports, and much more.

The most profitable commissions come from brands, though. Or rather, they did – until a recent Minecraft policy shift that shook the world of pro builders.

A change to Minecraft‘s Commercial Usage Guidelines announced at the end of May prohibits companies from commissioning Minecraftmaps or modifications that are meant for promotional purposes – so no more Minecraft adaptations of a big set-piece from the latest blockbuster movie and no in-game Verizon smartphones. In essence, anything that exists solely to promote a brand is off-limits.

“We want to empower our community to make money from their creativity, but we’re not happy when the selling of an unrelated product becomes the purpose of a Minecraft mod or server,” wrote Owen Jones, Mojang's director of creative communications, in a blog post explaining the new rules. Glixel reached out to Microsoft for more detail on these new policies but did not receive comment.

Build teams at the lower end of the market won't be affected much – they weren't getting these lucrative promotional commissions anyway. But for those at the top it means uncertain times ahead.

Banks says they've had to scramble to find companies and organizations that can pay for builds that won't be construed as marketing.

Their best bet going forward may be education, which is where Delaney says BlockWorks now gets the bulk of its commissions.Minecraft and Minecraft: Education Edition are used in thousands of schools around the world, and one flavor or the other is now a standard part of the curriculum in many schools across Scandinavia, the U.S., Australia, and elsewhere. These schools often need help designing and building the maps for Minecraft-centric lesson plans to help teach kids about everything from biodiversity and deforestation to sustainable living and city planning.

Some things are clear-cut no-go zones. Disney definitely can't pay a build team $10,000 to make a map of the climactic scene from the next Avengers movie. But there are grey areas. Can museums fund the creation of maps based on exhibitions they're running? Or could that be construed as promotional? One such project, Tate Modern's Tate Worlds, which features Minecraft re-imaginings of famous paintings, has already been taken down from popular server Hypixel because of the new rules, according to the map's builder.

The bottom line, as far as Banks is concerned, is that no matter how the blurred edges turn out under the microscope, this sets a worrying precedent for the future of professional Minecraft map making – and shows the precariousness of economic ecosystems built around corporate-owned games. And it could chase away – or force out – some of the best builders.

Banks says that if the build scene contracts, the servers will suffer – and so, in turn, will the game as a whole. “Minecraft is only limited by the creativity of the people who play it,” he argues. “The only danger it faces is if the ability for its player base to be creative is taken away.”

Meet ‘Minecraft' Builders Who Craft Impossibly Detailed Virtual Worlds