Oxygen Not Included

I have spent more hours than I care to admit watching carbon dioxide pool at the bottom of a poorly ventilated room, and I am here to tell you that is genuinely enjoyable. Oxygen Not Included sits in a category of one: a 2D colony survival simulator built around real-ish physics where every single decision has a delayed, compounding consequence. Gases do not vanish, heat does not teleport, and your Duplicants will absolutely stand idle in a corridor inhaling chlorine if you let them. That feedback loop, scarcity creating a problem that your solution turns into three new problems, is the engine that keeps hundreds of hours feeling earned rather than padded. The core loop starts simple. Three Duplicants, each with randomised skill sets and quirks, wake up inside a procedurally generated asteroid. You queue up dig orders, slap down an Outhouse, build a Microbe Musher for food, and pray the algae holds out long enough to get an Electrolyzer running. Pipe networks carry water and waste. Ventilation shafts route oxygen and scrub CO2. Power grids pull from coal generators, hydrogen cells, or manual treadmills if you are particularly sadistic. Each system is individually learnable, but the moment two of them interact unexpectedly, such as excess heat from your generator baking the water pipes that cool your algae farm, you understand why players invest hundreds of cycles into a single colony. The priority system for directing Duplicant labour is the roughest part of the early game; getting them to do what you actually want, in the right order, takes some patience and a few failed bases before it becomes second nature. For newcomers worried about the learning cliff: do not be. The game's onboarding is leaner than its reputation suggests. The first cycle gives you explicit prompts for food, oxygen, and sanitation, then steps back and lets the simulation teach you through consequence rather than tutorial walls. Yes, there are community YouTube guides stretching to dozens of hours for players who want to optimise SPOM designs (self-powered oxygen modules, a late-game staple), but a first playthrough does not require that depth. Start a Temperate asteroid on Survival difficulty, expect to rebuild at least once, and treat the early deaths as instruction. The randomised Duplicant selection at the print pod adds meaningful variety: a Duplicant with the Trypophobia trait genuinely cannot work near certain tiles, which forces creative labour routing. The procedural generation, meanwhile, means no two asteroids present the same resource distribution or biome hazard sequence. Post-launch support is worth acknowledging. Klei has shipped multiple paid DLC packs including Spaced Out, The Frosty Planet Pack, and The Bionic Booster Pack, expanding the asteroid roster and adding mechanics like radiation management, uranium refinement, and bionic Duplicant upgrades. Free bug-fix patches continue to ship as recently as early 2026. The mod ecosystem on Steam Workshop is substantial, with quality-of-life additions that address the one consistent criticism in long playthroughs: late-game performance degradation. Around cycle 300 to 500 on large colonies, autosaves noticeably stall and the simulation slows, an issue that appears to be a single-thread bottleneck rather than a hardware problem. Community mods can alleviate this, but it is a real friction point for players who chase the endgame rocket launches. The bottom line for the strategy-sim crowd: this is arguably the deepest colony sim available on PC right now, and it sits at a Metacritic score of 85 with Steam user sentiment well above 90 percent across tens of thousands of reviews. If your idea of fun involves routing liquid cooling around a steam turbine to generate clean power from a volcano, you already know you need this. If you are newer to the genre, the payoff curve is steep but legitimate. Just build the Outhouse first.

Diego · Scout Team

Strategy & simulation

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