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Overview
Oxygen Not Included drops you inside a procedurally generated asteroid with a handful of duplicants, zero infrastructure, and a clock already ticking on their oxygen supply. Developed and published by Klei Entertainment and released in July 2019, this colony simulation game operates on a deceptively simple premise: keep your people alive long enough to build something worth living in. The gap between that premise and execution is where hundreds of hours disappear.
The asteroid is not just a backdrop. It is a hostile environment with its own temperature gradients, gas pockets, alien biomes, and geological layers that complicate every decision you make. Dig in the wrong direction and you flood a room with chlorine. Forget to route your plumbing and your duplicants start drinking recycled sweat. The simulation runs deep, and it does not forgive sloppy planning.
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Gameplay and mechanics
At its core, Oxygen Not Included is a base-building and resource-management game where almost every resource loops back on itself. Your duplicants breathe oxygen and exhale carbon dioxide, eat food that generates heat, and produce waste that can be processed back into useful materials if you build the right machines. The systems interlock constantly.
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Key mechanics driving the colony sim loop:
- Oxygen generation and CO2 scrubbing
- Thermal management across rooms and biomes
- Food production, storage, and calorie tracking
- Stress management tied to duplicant morale
- Power generation and circuit load balancing
Duplicants are not just labor units. Each one arrives with a set of stats, traits, and personal quirks that affect how efficiently they work and how quickly they crack under pressure. A duplicant with a cooking skill shortage means your colony eats raw mush bars instead of proper meals, which tanks morale, which tanks productivity. The feedback loops are constant.
What makes this colony sim different?
Most colony builders let you focus on expansion. Oxygen Not Included forces you to focus on stability first. Oxygen is not a given. Heat is a threat that compounds over time as machines and bodies pump warmth into enclosed spaces. Managing temperature across a sprawling underground base requires understanding thermodynamics at a level that would feel at home in an engineering course.
The game's research tree unlocks new buildings and technologies, but each unlock tends to introduce new problems alongside new solutions. Building an electrolyzer solves your oxygen shortage but generates hydrogen and heat. Managing those byproducts becomes the next puzzle. That chain of cascading consequences is what separates Oxygen Not Included from more forgiving builders.
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World and setting
The asteroid biomes range from frozen tundra to caustic chemical zones, each with unique resources and environmental hazards. Alien lifeforms wander the rock and some can be domesticated, farmed, or used as part of a food chain if you engineer the right habitat for them. The world generates differently each run, which keeps the early-game discovery feeling fresh across multiple playthroughs.
Klei's art direction gives the game a clean, almost clinical look that contrasts with how chaotic things get in practice. The duplicants animate with personality, their stress reactions and idle behaviors adding a layer of dark humor to what is otherwise a relentless survival challenge.
Content and replayability
Oxygen Not Included includes multiple asteroid types and a Spaced Out! DLC that expands the game with a new cluster-map system, additional biomes, and space travel mechanics that push the late-game complexity considerably further. The base game already offers significant depth, but the DLC adds a second layer of logistical problems to solve across multiple asteroids simultaneously.
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The Steam Workshop supports a healthy modding community that has expanded the game with quality-of-life tools, new buildings, and additional challenge scenarios. For players who want to push colony survival simulation to its absolute limits, Oxygen Not Included remains one of the most demanding and rewarding entries in the genre.