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12m sales and counting: What's behind Cities: Skylines' building success?

We talk to Colossal Order CEO Mariina Hallikainen about why a seven-year-old game sold six million copies in the last three years

Finnish developer Colossal Order was founded with the aim of making one game in particular.

When the company was set up back in 2009, the goal was to make a city builder. It was a genre that had been popular in the past but any demand for this kind of game at the time was not being addressed.

Back then, Colossal Order was only five people strong; there was no way it could make something of that scope. So the company focused on one part of a city builder game; the transit system, and released 2011's Cities in Motion. Colossal Order pitched a whole city builder to Paradox after its debut but was told it wasn't ready, so Cities in Motion 2 came out two years later.

Now it had proven itself, the team finally wanted to make the city builder they had always wanted to create. A combination of Colossal Order's track record, as well as the disastrous launch of EA's SimCity in 2013, saw the studio given the green light by Paradox. This project, Cities: Skylines, was released to critical and commercial acclaim in 2015.

In June 2022, over seven years after the game's release, publisher Paradox recently revealed that Cities: Skylines has sold over 12 million copies since its debut.

"It's an unreal feeling," Mariina Hallikainen, the CEO of Colossal Order, tells GamesIndustry.biz.

"When we started developing Cities: Skylines back in 2013, I thought that selling 300,000 copies would be a fantastic result"

"It's been such a wild journey developing this game. 12 million copies... Who makes a game that sells that much? It's a great feeling to hit that kind of number. We never could have dreamed of such a thing. When we started developing Cities: Skylines back in 2013, I thought that selling 300,000 copies would be a fantastic result. That was the expectation: 300,000 copies. Since then, it's been completely unimaginable. It's a fantastic feeling to have created something that is, in a way, timeless."

One thing that is notable about Cities: Skylines' sales is that they have actually sped up in recent years. Of the 12 million copies sold, six million were bought in the four-year period between its initial release in 2015 and 2019. The other six million were sold over the following three years.

"I'm gonna be very honest, I have been waiting for the point when sales start to decline," Hallikainen admits.

"We're not in a normal situation with this game. We did see a lot of people coming back to Cities: Skylines in the last two years with the pandemic. People started to spend more time with the game, so that must have had some sort of an effect. One of the things, of course, is the increased marketing and community effort that Paradox has put into this game as it comes to new platforms; that's something that has kept the game fresh and in people's minds. So just that kind of continued support. We have made a lot of new content for the game. Before the pandemic, we were releasing around one to two expansions each year.

"Of course, with games, there's sometimes something we can't explain. We don't 100% know why one game succeeds and why another doesn't. It can be something that we can't really measure. It makes game development frustrating but also very exciting. I don't really have a proper answer as to why this has happened with Cities Skylines."

Colossal Order is only responsible for the PC version of Cities: Skylines, while Paradox handles all other versions of the game. As a result, Hallikainen isn't able to give any kind of sales breakdown of that 12 million copies across different platforms. She is, however, able to say that PC still takes up the biggest slice of the pie -- perhaps unsurprising given it launched several years before the game's other versions.

"The majority of our efforts go towards the PC version for sure," she says. "And I think that is where the biggest audience also still remains."

Part of the reason that Colossal Order focuses entirely on the PC version of the game -- and a contributing factor to its success -- is modding and the freedom that comes with being on PC.

"Player freedom is one of the core pillars of Cities: Skylines," Hallikainen says. "But I think it's really the community's self-expression. With Cities: Skylines, I like to say more is more. If you think about the size of the game when it came out and the amount of content there is for the players for free on the Steam Workshop, that is so much content. Between that and the content we have made, there is so much to choose from.

"We have the independence that we craved when we started the company. We have no VC money in the company. We don't have to plan for an exit. We don't want to sell"

"If players want to create something, all the tools are available to them. Or if you want to create something of your own, you can share it with the community. You can basically express yourself and put your own stamp on the game. That is the heart of the game, and why it is so successful and loved.

"Back in 2013, when we started to work on Cities: Skylines, we had two programmers. One focused on gameplay and the other one focused on the modding tools. We understood that we won't have as much gameplay content as we could, but we wanted to put the effort into the modding tools so that people can create something of their own for the game."

When Colossal Order started working on Cities: Skylines, the company had only nine employees. By the time it was releasing the game, the outfit had grown to 13 members of staff. At the time of writing the company has just 30 employees, according to Hallikainen. That does mean that the developer has doubled in size since Cities: Skylines was released, but given the game's blockbuster success, one might expect the company to have grown even further.

"We are not planning to sell Colossal Order," Hallikainen explains. "The company is owned by five people who all work at the company still and enjoy immensely the freedom we have when we get to work on projects we absolutely love. We get to choose what we do next. We have the independence that we craved when we started the company. We have basically no VC money in the company. We don't have to plan for an exit. We don't want to sell the company. We don't have to groom the company to become something big and sellable, so to speak.

Colossal Order CEO Mariina Hallikainen

"What we want to do is work with great people, hire talented individuals who share the values we have in the company. We want to be an employer where each individual feels respected, and safe to be able to express themselves and participate in the game development process.

"So it doesn't matter if you are working in QA or whichever department, art, code, or design, you have a voice. It's easier to maintain these values when the company stays smaller. We want to grow the company so that we have the talent we need, but we are not trying to hire like crazy.

"It's very difficult to find employees in the current climate. There is a lot of competition for talent. The growth itself shouldn't be a value in itself. The choices we have made in the company haven't always been financially the most beneficial to the owners, for example, but it is something that we value our freedom. We want to work in a certain way, so as long as we keep our independence and do things our way, there is no reason to go crazy. Of course, it means that we do things quite slowly. There's always a downside. We could be a bigger company but we have decided to not go that way."

COVID-19 and the resulting lockdowns are no doubt a factor in Cities: Skylines' continued success and its sales acceleration in recent years. People around the world were stuck in their homes and looking for entertainment. But the pandemic hit Colossal Order hard.

Until the start of 2020, the studio had been releasing a number of expansions each year, as well as other post-launch content. In March 2020, the company released the Sunset Harbor DLC. This would be the last piece of content to come out for Cities: Skylines for almost two years, with the Airports expansion finally arriving in January 2022.

"You can basically express yourself and put your own stamp on the game. That is the heart of the game, and why it is so successful and loved"

"The pandemic was a huge disruption," Hallikainen says. "We all had to work from home. There was so much uncertainty. This kind of creative work is emotionally straining. You give so much of yourself working in a creative field. There was such uncertainty outside of work; the entire world was in chaos. Absolutely everyone felt the negative effect of it. It was something that easily messes with productivity and how things are made. It took us a while to kind of get to our normal efficiency level back."

At this point in the game's lifecycle, one might expect Colossal Order to start winding down development on Cities: Skylines and maybe focus production on a new game. But that's not the plan -- at least not for the moment. Though the pandemic slowed down work at Colossal Order, it also gave the studio a bit of space from Cities: Skylines. As a result, the company is experiencing something of a second wind with the game.

"We've found a new spark and passion for Cities: Skylines in a sense," Hallikainen says.

"It's been exciting to work on the game again. When you work on a project for such a long time, it becomes less exciting. It becomes very normal. It's just what you do. Like everyone everywhere, we experienced challenges during the pandemic. But I believe that for us it was good to have a break, find what's important and really get back to finding what's exciting in game development. It's looking really, really good. We definitely are eager to bring more to Cities: Skylines.

"So I don't know when it makes sense to stop working on Cities: Skylines. Of course, we have been wondering when will people have seen enough of the game. But as long as we are still excited about what we are doing, there is still room for growth with Cities: Skylines."

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Alex Calvin


Alex Calvin is a freelance journalist and writer covering the business of games, and has written for the likes of GamesIndustry.biz, Eurogamer, Kotaku UK, VGC, Games London, The Observer/Guardian and Esquire UK. He can be found on Twitter @gamesbizuk.