Duplicant Story

Lore & Background

In the world of Oxygen Not Included, Duplicants are a small, round-bodied species that arrived on a barren planet with nothing but a lander and a handful of tools. The planet's cross-section is a layered cake of rock, soil, and gas pockets, and the Duplicants must carve their civilization out of it one tile at a time. Their biology is simple but unforgiving: they must breathe oxygen, drink water, eat food, and stay within a comfortable temperature band, or their moods plummet and their bodies fail.

What makes the Duplicants compelling as a species is their individuality. Each one carries a set of traits—some love the cold, others hate the dark, some work faster in certain roles, and some are simply more resilient. They express their state through small, expressive animations: a happy Duplicant bounces; a very sad one slumps and sulks. The colony's success is measured not in grand conquests but in the quiet, daily rhythm of keeping every single one of them fed, hydrated, and breathing.

Over the course of a playthrough, the Duplicants evolve from a desperate handful huddled in a starter habitat into a thriving community with agriculture, research labs, and even small luxuries. The player's relationship with them is one of caretaker and engineer: you are not commanding an army, you are managing a fragile ecosystem of tiny lives that depend entirely on your planning.

In Their Own Story

The alarm chimes at 03:00 colony time, and Pip stirs in her bunk, ears flattening. The O₂ gauge on the wall reads 18 kPa and dropping. She pads barefoot across the cold metal floor, her small body hunched against the chill, and presses her palm to the recycler's housing. It's warm. Too warm. The fan is clogged with dust again.

Three meters away, a very sad Duplicant named Brol sits on the floor, arms wrapped around his knees, watching the oxygen numbers tick down. He doesn't move. He can't. His mood is in the red, and his hands won't obey the command to grab a wrench.

Pip doesn't yell. She doesn't have the energy. She just picks up the wrench, walks over, and starts clearing the intake grille, her tiny fingers working fast. The fan kicks back to life with a shudder. The gauge stops falling. Brol watches. After a long moment, his ears perk up. He stands. He walks to the water dispenser, drinks, and goes back to his bunk.

The colony breathes again. For now.

Reader's Guide

Species: Duplicant (base)

Core Needs: Every Duplicant continuously consumes O₂, H₂O, and food, and must remain within a comfortable temperature range. If any need hits zero, the Duplicant's health degrades and they will eventually die. Temperature outside the comfort band accelerates mood loss and, at extremes, health loss.

Mood System: Duplicants cycle through four mood states—Happy, Neutral, Sad, and Very Sad. Mood is influenced by need satisfaction, environmental factors (light, noise, temperature), and individual trait preferences. Work efficiency scales with mood: a Happy Duplicant works at full speed, while a Very Sad one works at a heavily reduced rate.

Work & Roles: Duplicants can be assigned to research, construction, agriculture, and other tasks. Their speed and efficiency in each role are modified by their traits and current mood. A Duplicant with a relevant trait bonus will outperform a neutral one in that specific task.

Traits: Each Duplicant has a small set of passive traits that grant bonuses or penalties in specific situations (e.g., tolerance to cold, preference for certain foods, work-speed modifiers). These make each colonist functionally distinct and reward the player for matching assignments to individuals.

Restrictions: Duplicants cannot survive in a vacuum or in extreme temperatures indefinitely. They require a sealed, pressurized, and thermally regulated environment to remain functional. They do not regenerate needs on their own; the player must engineer a sustainable supply chain.

Did You Know?

• A Duplicant's mood directly scales their work speed, so a colony full of Very Sad workers grinds to a near-halt even if all their physical needs are technically met.
• Each Duplicant's trait set is unique, meaning two colonists with identical needs can have very different optimal living conditions and work specializations.
• The game's 2D cross-section view means that gas (O₂, CO₂, etc.) and heat behave as fluids that pool, flow, and stratify—so where you place a Duplicant's bunk can matter as much as what they eat.
• Duplicants express their emotional state through small, readable animations—bouncing when happy, slumping when very sad—giving the player immediate visual feedback on colony morale.