Oxygen Not Included, developed by Klei Entertainment, isn’t just about keeping duplicants alive—it’s about mastering an interconnected web of systems where one oversight can unravel your entire colony. By the mid-game, the simple survival strategies of algae diffusers and planter boxes won’t cut it anymore. You’ll need to think bigger, optimize smarter, and prepare for late-game challenges that demand precision and foresight. Here are five tricks to supercharge your colony’s mid-game and set yourself up for long-term success.

Mastering Steel Production Early

Once you unlock the Metal Refinery, steel production becomes one of the most critical steps for mid-game progression. Steel is essential for high-heat environments and advanced structures like the Steam Turbine. But refining it generates enormous heat. A clever trick is to submerge your Metal Refinery in a liquid cooling loop, ideally fed by a dedicated coolant like petroleum or super coolant later on. Pair this with an Aquatuner for precise thermal regulation, and you’ll avoid melting your infrastructure while cranking out high-value steel.

Infinite Storage for Liquids and Gases

Resource sprawl can cripple efficiency, but mid-game introduces a game-changing technique: infinite storage. By using liquid locks and controlled venting into tile-based storage designs, you can condense hundreds of tons of gas or liquid into a single tile. This not only saves space but keeps your colony organized. Infinite storage also allows you to stockpile critical gases like oxygen or hydrogen for emergencies, ensuring stability when demand spikes.

Managing Duplicant Stress and Traits

By mid-game, duplicants start showing quirks that can derail progress—vomiters contaminating water supplies, binge eaters wrecking food stores, or destructive dupes smashing your batteries. Instead of avoiding “problematic” dupes altogether, smart colony design can mitigate these risks. Isolate stress-prone dupes in morale-boosting rooms, use decor-heavy barracks to offset stress penalties, and strategically assign jobs to minimize breakdowns. Leveraging the morale system and room bonuses can turn a liability into a functional worker.

Liquid Stacking for Efficiency

Water and polluted water are lifelines, but managing them efficiently is a technical hurdle. Liquid stacking—using carefully placed tiles to layer different liquids—allows you to segregate resources in tight spaces without massive reservoirs. This is especially useful when running Water Sieves or managing outputs from bathrooms, as it prevents overflow disasters and ensures a stable supply chain. A well-designed liquid stack system means less micromanagement and fewer panic moments when your water lines clog.

Prioritizing Engine and Power Upgrades

As your colony expands, power demand skyrockets. Relying on coal and manual generators will bottleneck progress. This is where mid-game power upgrades shine. Transition into natural gas generators or hydrogen generators for higher efficiency. Pair them with smart batteries and automation wires to prevent overproduction and wasted fuel. Early investment in these systems frees duplicants from constant manual labor and stabilizes power for critical operations like refining, research, and advanced farming systems.

Conclusion

The mid-game of Oxygen Not Included is where casual colonies collapse or future megabases are born. Steel production, infinite storage, duplicant management, liquid stacking, and power optimization aren’t just survival tricks—they’re the foundation for thriving in the late game. By leaning into these technical strategies, you’ll transform your struggling underground outpost into a streamlined, self-sufficient machine, ready to tackle the game’s toughest biomes and challenges.