With strong sales, positive reviews (ours is here), and thousands of player-made assets and mods, Cities: Skylines has quickly become one of 2015's hits. I spoke to Mariina Hallikainen, CEO of developer Colossal Order, over Skype on Wednesday, and asked her about the origins of Skylines, 2013's SimCity, mods and modders, and plans for the future.

PC Gamer: Considering that you set a Paradox sales record at launch, you've sold a half-million copies of Skylines, and that both the reviews and the reaction from players has been almost entirely positive, can I assume your offices now actually resemble the massive Colossal Order skyscraper that's in the game?

Mariina Hallikainen: [Laughs] We're still in the same office, we moved over here just last January so there's no need for anything too different from that. We're of course very happy. We're very pleased.

It's pretty common in discussions about Skylines to see 2013's SimCity being brought up. While it sold well, it's clear a lot of people were disappointed with some of the choices Maxis and EA made. When Skylines was being developed, was SimCity something that was discussed often at Colossal Order, and was there an effort to deliberately avoid some of the same choices they made?

Mariina Hallikainen

Yeah, that's a tricky question, because of course, we always have thought of SimCity 4 as the benchmark. This is due to the fact that we actually did plan this game when we started the company back in 2009. We started to think about... Colossal Order wanted to make a city builder some time in the future. We knew we couldn't do it right from the start because we were five people. I started the company with no experience on the PC platform. The guys had been working on mobile before Colossal Order. It was really something that ideas kind of came from, really, the classic city builders.

But of course we were extremely afraid that people will just think of us as a cheap knock-off or something, that we have been just trying to copy what they did in SimCity. So it was a little bit of a daunting task for us. But of course there are things that are very similar and I guess it's kind of unavoidable in a sense that the city building genre, I think, it's based on the great SimCity. So it's something that we knew we would be compared.

Was Skylines already actively in development when the 2013 SimCity came out?

It was not actively in development at that time. When they announced [SimCity 2013] I was pretty sure there was no way we would ever be able to convince Paradox that we should make this game. [Laughs] But, yeah, they gave us the green light after they saw what happened with SimCity.

So that was actually... seeing SimCity 2013 kind of stumble, that's when Paradox said, hey, maybe we should go ahead with this since people aren't really happy with the last SimCity?

Yeah, I think it must have helped a lot.

Now, when I was playing Skylines pre-release, some people knew I was playing it, and one of the questions that most of them asked was, is there a multiplayer mode? Did you consider any kind of multiplayer for Skylines at any point?

No. Basically, we are of course with very limited resources and with the small budget we have, it was completely out of the question. Even if we think about... we have a certain philosophy behind the game, and it is definitely so that it is really a singleplayer game. It's you creating your own city, your own world. You don't want anybody to kind of come and mess that up. The experiences we've had previously, we decided that we will go singleplayer only, at least for now.

Yeah, I'm not even really sure how multiplayer would work. I think there's a collaborative potential, its fun to sit with someone at the same computer and build a city together, and our guy Tom was streaming the game a few times last week and he had fun with the people watching, taking suggestions and things, but I don't really know how a multiplayer city builder would work with two people messing with the same city at the same time.

Yeah, that's exactly the problem, I think, and especially because there's the simulation running, there's so many things that can go wrong, I think it's something that you really have to put a lot of effort and a lot of people to work on that, to make it really work and be right, and so we definitely didn't feel that it was important to do at this time. And, I don't see it as a high priority feature at any time in the future, because there's still so many things we want to add to the game. We have quite a lot of plans, those things we couldn't implement before the release, like tunnels and European buildings that we are working on now. I think there's a lot of things we want to add to the game before we can even discuss multiplayer.

So you do have plans for future updates, or is it a DLC type thing?

So, basically we have discussed it with Paradox and it's going to be a similar model to what they have for Crusader Kings 2 and Europa Universalis 4, so it's a bigger expansion with some smaller DLC and also free content. The tunnels and the European buildings we already discussed that these would be free updates, because I very strongly feel that the tunnels, for example, should have—I feel it's a part of the game. It's an integral part of the game and it needs to be there. So, we agreed that we, of course, having only 13 people working at Colossal couldn't make it in the original scope, we really just want to add that later on, and I think it belongs to all the players.

You compared the future expansions to what Paradox does with CK2 and EU4. Those are, a lot of times, different parts of the world or different time periods. Is that something that Skylines is going to have?

No, it's more to the scope. Basically, how we did it earlier with Cities in Motion, for example, we had smaller DLC and we were working on those, but here we want to kind of focus on one bigger feature. I can't say what those are exactly at this time, but we are planning on something that really brings something new, hours of gameplay to the game. So, massive expansion.

I can't say more about the pricing but it's something similar to what they have done with CK2 and EU4. Simultaneously with this we add free features and free content to the players who already own the game. So, the players who don't want to put any money to extra content, they still get something out of the version. This is what we're planning, there's always like this bigger expansion that will bring a lot to the game, then the free updates as well probably [smaller] DLC. But it will be so that it comes with a full package that has all of this, the paid and the free update for the player. Which I think is really nice, because we get to focus on something more major and then also there will be the free update, because I think it is important that the players who have bought the game now and for some reason don't want to, for example, put any money to a certain expansion, they can kind of pick and choose what they want but still get something, something like updates to the game so you don't have to pay for absolutely everything. I think that's very cool.

Are there any plans for a terrain editor you can use while you're actually working on a city?

We have discussed that. There is no news about that yet. So, basically—terraforming has been actually discussed quite a lot. It is a little bit of a tricky feature so we need to think about it a lot to see if it would be possible or not. We have some ideas. We'll keep you guys updated on that

Given the successful sales of the game, do you think that's changed the scope of future expansions? Do you feel like you have a little bit more room to grow because the game has sold well?

Well, [Paradox] is very happy. [Laughs] It is something that we have discussed that now we have a chance to add more to the game both in the scope of the planned expansions and for the free content as well. One of the major differences now after these really massive sales—it's still a little bit overwhelming for us over here—is support for the modding. So, we're basically discussing that we really want to emphasize that, we want to bring more to it, so we definitely got more support, also from Paradox to work on that, which is absolutely fantastic.

I checked this morning, and there's over 13,000 player-made assets and mods in the Steam Workshop at the moment. Have as anyone at Colossal Order been trying them or playing with them or seeing what people have been up to?

Yeah, I mean, we've been checking what's happening there and it's really, really great to see, because last time I checked it was 12,000. [Laughs] So, the number keeps going up. It's absolutely fantastic. I think this is exactly what city builders are all about. It's about the creativity, getting the people to join the development of the game, and I think this is absolutely wonderful to see, so many people actually joining the modding community, and yeah, we've been checking. There's actually really, really cool stuff. We have been checking out the different kind of mods, too. Because there are so many things that we kind of planned to do later and the modders basically already did them. So, we have to say a little bit... are we needed anymore? [Laughs]

Right! Yeah, there seems to be a few things in there that you could possibly officially add in a future patch. People have been... one of the first things they did was unlock so you could build on all 25 tiles. And then a few other things that look like they could be possibly incorporated into an official patch at some point.

Yeah, absolutely, there's so many things to choose from, but I think most interesting ones are kind of those that... like the GTA V map, there's the Mars project. So much creativity, and you know, things that we couldn't kind of think when we entered this project, that people would come up with these kind of ideas and I think that's exactly the great part about this. Because we're only 13 people here, but there are so many ideas out there, so many capable people that can really contribute to this game.

I even saw there's a former Maxis artist who's making mods for the game, have you seen that yet?

Yeah, I saw the article on that, yeah. I think it was on PC Gamer, actually. Yeah, yeah, um. [Laughs] I mean, it's really, really great to see people starting to create content for the game and we of course welcome... [Laughs] welcome really capable environment artists to do that as well. So, it's really interesting to see.