Karoliina Korppoo is the lead designer of Colossal Order’s remarkably successful Cities: Skylines, and while deconstructing the game at GDC Europe today she encouraged developers to focus on rewarding players for learning, rather than punishing them for failure.

“If you have the greatest game in the world, but nobody knows how to play it, it’s not the greatest game in the world,” says Korppoo. “If you think about Diablo III, one of my favorites, it’s all about teaching players how to play the game.”

What ties Diablo III and Cities: Skylines together, she says, is a shared emphasis on punishing players as little as possible and gently guiding them to figure out the game on their own using subtle, integrated tutorial systems.

“Learning and helping them out, guiding them towards finding new features and learning more, that’s how a game should reward the players,” says Korppoo. “It seems to be working quite nicely for us.”

When a player doesn’t learn something, the failure to optimize something is punishment enough — Korppoo says Colossal Order doesn’t put a lot of effort into punishing players for failing to achieve objectives.

Punishment is overrated

“If you are going to play a city-builder, you want to build a city that matches the ideal in your head,” says Korppoo. “If the city isn’t working, that’s your punishment — and that’s enough.”

Now six years old, Finnish indie studio Colossal Order built Skylines with a team of 14 people — a chief, a social media manager, 2 designers, 3 programmers, 5 artists and a QA manager. Working with limited time and resources, the studio returned to Unity for the second time rather than trying to revive its own in-house engine tech.

“With the first game we made, we had a long time to develop it before actually making a publishing contract,” recalls Korppoo. “We had a much longer development time than usual, and so we had time to work on our engine.”

When the time came to do Skylines, she says the old engine needed so much update work — and was so time-consuming to work with already — that sticking with Unity made more sense than trying to update Colossal Order’s in-house tech to run smoothly on modern PCs.

Korppoo says the team went with PC over mobile for Skylines because its where the studio’s development strengths lie, and more importantly, mobile platforms don’t readily support the complex city-builders the studio makes.

“Our target audience is traditional,” says Korppoo. “They want to play on PC, they want to play for a long time, and they want to pay for a full game and not pay extra for micro-transactions during the game.”

That snugly fits into publisher Paradox Interactive’s bailiwick of grand PC strategy games, and Korppoo believes that Paradox’s efforts to market Skylines to its audience of strategy enthusiasts contributed significantly to the game’s success. If you have the chance, she suggests, make a deal with the publisher whose audience and mission mesh with your own -- not with the one offering the biggest paycheck.

Korppoo also recommends that you not be afraid to look at what other developers are doing, and learn from their work. The designer says Skylines succeed in part because it improved upon the weaknesses of prior city-building games, rather than trying to reinvent the wheel.

“If I polish the things that already exist, it will be much better than trying to create something new, a perfect gem of game development,” says Korppoo. “Using old stuff that’s been proven is a great way to go, because its familiar to players.”

This extends beyond the game's systems, which are more complex than the 2013 SimCity but less complicated than Colossal Order's previous Cities in Motion 2, into the visual aesthetic of the game. Korppoo says the studio took significant visual inspiration from the latest SimCity because it "looked really awesome," but the team also dug deeper into the history of city-builders, looking at early versions of SimCity as well as Sierra city-builders like Pharaoh and Zeus: Master of Olympus.

When choosing the right visual style for Skylines, Colossal Order ended up adopting a generic North American cityscape for its easy readability and flexibility.

“We went with this imaginary North American city, because it had lots of these detached houses that are nice to work with,” says Korppoo. “They conform to the territory really well, and it’s easy to see how many people are living in an area.”

The studio wound up abandoning traditional tutorials after some bad experiences on past projects, which had used the traditional system of shuttling players to standalone tutorial maps to teach specific gameplay mechanisms. Instead, the studio tried to build an unobtrusive “guide system” into Skylines that would show players context-sensitive guiding messages.

“With the integrated message system, if players forget something they’ll get a notice anyway, and they don’t have to play a tutorial,” notes Korppoo. “It gets around the fact that many players won’t play a tutorial, even if they need it.”

Give players enough rope to save themselves, and they'll hang around

Skylines doesn’t really have a “Game Over” state, and Korppoo says this again stems from Colossal Order’s philosophy of designing games that encourage players to learn how to play well, rather than punishing them for playing poorly.

“If the player is in a bad situation, and the rescue the city, they become attached to the city and want to play the game more,” says Korppoo. “We want players to feel they’ve done something for the city that’s working, and they get this feeling of achievement.”

They also earn in-game achievements for hitting certain milestones, and are rewarded with unique buildings that can then be used in other cities. Korppoo says Colossal Order settled on this reward scheme after observing that players were formulating new ideas for cities hours into an initial play through, and allowing them to carry reward buildings over into new games encourages them to keep playing without punishing them for abandoning a city.

“When you make your first city, it’s probably not going to be awesome; it’s likely to be quite awful,” says Korppoo. “But this doesn’t matter, because if you get an achievement you can use the unique building you’re rewarded with in a new city.”

The studio also put quite a bit of effort into making Skylines moldable, and Korppoo believes it paid off handsomely by keeping people playing (and talking about) the game after the initial shine wore off.

“If you’ve ever played a city-builder, you know the point where all the parks look the same, and it’s boring,” says Korppoo. “It helps to let players create assets, because they fit into the standard game and bring something new to the experience.”

Skylines has different levels of mod approachability: players can make maps with the map editor, create buildings and other assets with the asset editor, or create whole new game systems with Skylines’ modding API.

“Someone made a new AI for the garbage trucks, and it works really nicely,” says Korppoo, by way of example. “Now even I use it.”

But this brings up an interesting quandary: How should Colossal Order go about updating Skylines and adding new features when the game also has a vibrant mod community? Is it okay for the studio to take direct inspiration from mods, and if so, how should it give credit?

For now, the studio seems to be sidestepping the credit issue by only using user mods as guides and indicators, not blueprints.

“It’s interesting to look at which mods are the most popular, because that’s an easy way to see what people want in the game,” says Korppoo. “we’ve decided we’ll make some features that are like the popular mods, but not exactly the same; the popular mods are really perfect as guides for what people want in the game.”