With Oxygen Not Included, Klei Entertainment, developers of harrowing, sometimes-hilarious survival game Don’t Starve, tasks players with surviving in an even more inhospitable environment: outer space. Oxygen, minerals, water, entertainment, and a place to just exist within provide all new-challenges to players.

“We didn't start out intentionally creating a survival experience," says Graham Jans, one of the developers of Oxygen Not Included. "We're always trying to do something different with each game we work on. Oxygen Not Included came from a very different motivation than Don’t Starve.”

The initial concept took elements of what would be required to survive in space and building interconnecting systems and simulations. Certain aspects of the game’s world would behave in predictable ways, allowing players to manipulate them in order to achieve desired outcomes.

“When development started on Oxygen Not Included, one of the desires was for the whole game to run on a broad (though simple) simulation. It feels like a very complex, living world when you play it," says Jans. "But in fact, it's mostly an illusion. Other than the way fire spreads, there's very little simulation running under the hood; the rest is simple behaviors and magic happening just off the player's screen.”

“Much of the early design was bottom up, creating the temperature, pressure, and chemical simulations that you see in the game now, and developing the gameplay within the challenges that simulation provided,” says Jans. 

As those challenges started to come together, the developers found themselves with a whole different kind of survival experience than what they’d crafted before, taking them to all-new territory that required new ideas as well as the knowledge drawn making Don’t Starve.

Simulations to survive in

Oxygen Not Included features many different systems of simulation, all occurring at the same time. Air systems are in place, dictating flow of oxygen, how it behaves based on the internal state of the player’s hideout, how much a character needs to reach certain states of comfort or survival, how it reacts to other elements, and several other key aspects of its behavior.

Air is but one of the simulations going on within Oxygen Not Included. There are many, many more that dictate the various other behaviors of characters and objects, and it’s through managing all of these that the developers created a wholly different game from their last title, yet still found themselves in a position of creating a game about players struggling to survive.

“We started by playing with systems and figuring out what interesting challenges emerged. Of course, now that development has progressed and our systems are better understood, we've continued explicitly designing challenges on top of the systems.” says Jans.

Jans says that the biggest challenge, both for Klei and players, is that every aspect of the game is now part of a closed loop. "In most games, you can at least take air or ground for granted, but in Oxygen Not Included, every pixel on the screen represents some kind of limited resource,” says Jans.

“Not only that, but because of the closed nature of the system, we have to be vary wary of mass conservation as well," he adds. "Everything that has an input needs to have some kind of output, so that all the air, minerals, energy, and so forth can keep flowing around in these ecological and industrial cycles and sustain a thriving base. Not every gram is perfectly conserved - we do a lot of hand-waving - but there is a strong sense of sustainability when you are playing, and it's extremely challenging to tune and add new features to the game without destroying that balance.”

Not starving in space

This was a very different experience from Don’t Starve, forcing the player to continually recycle what they have within a closed system of interconnected, complicated simulations. That’s not to say the developer couldn’t take any of their past work lessons into Oxygen Not Included.

Oxygen Not Included was not made as a successor to Don't Starve, but as both games ended up focusing on the inherent struggles of living in a dangerous place," says Jans. "We've definitely been able to take across a lot of lessons.”

“Foremost among these is being careful about how we layer and overlap our challenges. The obstacles in the world are meant to be persistent -- your Duplicants (characters) never stop breathing, after all! -- so even when you've got oxygen production thoroughly solved, suffocation is still a threat lurking in the background, daring you to make a mistake,” says Jans.

The developers had seen that survival would be at its most tense should the player constantly have a flow of small challenges layered on top of one another, and at no point ever offering the player a sense they were completed. Hunger could be staved off for a while, but that need would crop up again soon. While players would be able to build systems that may be able to take care of air or heat problems in space, those solutions could never be final. There would always need to be a way in which they could go wrong.

“Also, no particular obstacle is supposed to be particularly difficult  — it's the layering that makes intense decisions," says Jans. "In Don’t Starve, it was make light, while collecting food, while collecting construction materials, while defending yourself from creatures... all while preparing for winter. This is the same kind of layering we strive to do in Oxygen Not Included, where the player must balance all the needs of their dupes at the same time. Each need is not so difficult, but it's easy to let something slip while you're working on your next megaproject.”

There is no singular problem that the player has to surmount when they play Don’t Starve, but rather several of them all going on at once, and the player has to prioritize their actions in order to best stay alive. This layering of challenges formed the backbone of Don’t Starve, and later on became an important part of surviving in space with Oxygen Not Included.

Another special element of Don’t Starve that carried over was the lack of obvious tutorial, forcing the player to (feel like) they’re learning everything on their own. “The other major takeaway from Don’t Starve is how we can design a game that has little or no tutorial,” says Jans. “Don’t Starve does a wonderful job of silently but surely leading players through its mechanics using only gameplay. Oxygen Not Included is a significantly more complicated game, but we still strive to teach people how to play through natural discovery and helpful UI rather than dragging them through a tutorial.”

A fun part of surviving, as Jans would see through Don’t Starve, came from learning how to keep yourself alive on your own. It’s not that developer would completely toss the player out on their own, giving them small hints on what to do to live, but that players enjoyed it most when they felt that they’d wrested themselves from danger using their own wits. Part of that appeal of surviving came from figuring out what you needed to do to live.

The ‘fun’ in avoiding your funeral

With these systems, Jans hoped to make for an entertaining survival system for the players of Oxygen Not Included, letting players work through each system in creative ways to solve the game’s challenges, as well as those the player could create for themselves.

“When players come to a game, there's often a certain amount of punishment they expect just as part of playing," says Jans. "Humans like throwing ourselves against challenges and seeing if we can overcome them. When you start playing with the simulation in Oxygen Not Included, it's quite easy to dream up challenges for yourself: Can I turn that water into steam? Can I redirect that water into my reservoir? And so forth. Then, as you try and complete that challenge, the simulation kicks back in unexpected ways and you've got a happy disaster on your hands.”

Those happy disasters provide opportunities for players find new solutions, continuing to push that creativity the developers want from them. It’s no fun in a survival game if the player finds a perfect solution to any given systemic problem, and so the system has to fight back in its own interesting ways, finding things players don’t think about or creating issues in other ways. Again, we see the layering of needs that came from the developers’ work on Don’t Starve.

For the developer, this means they have to constantly come up with new ways in which the systems can interact with one another, finding different ways to make the player need to manage varied aspects of the systems, and how they can create a system that always challenges the players with something going wrong with it feeling like they are purposely trying to make something go wrong all the time.

“The challenge for us has been determining which of those scenarios we want to provide tools for the player for, and which scenarios will become essential to the short term and long term survival of your colony.” says Jans. “We then try out different buildings and Duplicant needs that will motivate the player to care about temperature management, or liquid plumbing, or electrolysis, or whatever the interesting challenge is.”

It hasn’t always been a smooth process for Jans, either, requiring lots of iteration and playtesting to see how it all works together. “Because the simulation is so comprehensive and interconnected, there's also tons of tuning and tweaking to ensure that the solution to one problem doesn't defeat or obsolete the solution to another problem.”

“For example, say we tune down the amount of metal in the starting region for balance reasons. Now, the player has to dig out more open space in order to extract all the metal, which requires them to produce more air than before. In addition, metal ground quickly absorbs heat, so less metal means the natural heatsinks for your warm industrial buildings start to disappear. Every decision we make ends up having these sorts of gnarly chain-reaction tuning challenges.”

Even the game’s happiness system, which dictates just how pleased a given Duplicant is, helps further complicate this. “After you get your dupes' basic needs met, you have to start dealing with more 'sophisticated' problems such as the quality of the decor. It creates a very natural progression to the kind of challenges you need to overcome to create an ideal colony. We're still mostly dealing with basic needs at this point in development, but the mental and emotional needs of the dupes provides us with a lot of opportunities for new challenges.” says Jans.

“Even basic needs like oxygen gain degrees of complexity this way: I have enough air to not die, but it's kinda low pressure so it causes me stress. This way players have a chance to solve their basic problems in whatever simple or brute-force way they can come up with, and over time, refine their solutions or look for better solutions. This way both beginner and advanced players can feel like they're tackling the same problems and get a sense of improvement, without us having to invent whole new systems each time the previous challenge has been met.”

Due to these decisions, Oxygen Not Included becomes an evolution of Don’t Starve, in a sense. The systems and their interconnections are more complex than the varied needs of the previous game, but the developers have still tossed the player into a lonely world with little explanation, forcing them to play around with the systems to see how they work together. Survival still depends on the player’s hard work.

Not only this, but all of the player’s challenges are layered, with each system connecting with the others in varied ways. There is no one single problem the player has to juggle, but a series of problems that all tie into one another, forcing the player to constantly juggle them like in Don’t Starve. As such, while Oxygen Not Included comes from a very different mindset than Don’t Starve, many of its lessons still carried over into their next work in survival.