History YMMV / OxygenNotIncluded

** The inability to take direct command of the duplicants for tasks can get really bothersome. Even if you bump the priority of something up to the max nine and directly move the duplicant to what you want them to do, there's no guarantee they'll ''actually do it''. For building base walls and the like it's usually fine. For smaller but necessary tasks like farming or cleaning the outhouses? Expect the colony to die of starvation because no one wanted to farm, or duplicants peeing in the fresh water supply because nobody wanted to clean the outhouse. This is especially bad if a duplicant traps themselves in some way; even when in red alert mode, you can expect the duplicants to prioritize painting pictures, restocking coal generators and building stations instead of digging the trapped duplicant out until it's too late.

* Headscratcher:
** If these dupes are here because Gravitas launched the printing pod onto the asteroid, how is there already an (abandoned) Gravitas office building on top of the asteroid?

** Diver's Lung is widely regarded as ''the'' best trait a duplicant can have. Not only does it allow them to spend more time in oxygen deprived areas, allowing them to venture further out of the base before one gets exo-suits, it also lets oxygen in the base go ''way'' further than a colony of duplicants without divers lung. It's possible for a self-powered oxygen machine to make a large base of twelve or so duplicants easily breathable simply by a majority of those duplicants having the divers lung trait.

* UglyCute: The dupes themselves. Also pufts.

* ThatOneLevel: Swamp biomes. Heavily populated with germs, and duplicants are almost guaranteed to get Slimelung from it, which can kill them if not dealt with quickly. It also can very easily spread through the colony like wildfire. What makes Swamp biomes so hard is that they often generate right next to the base; sometimes surrounding it on all sides, which makes it impossible to avoid.

** Heck, Puft Princes are this {{in-universe}}, considering that they have a positive decor value.

** Just algae in general until you can get the relatively late game upgrades that make it obsolete. One Let's Player described the game as "find algae, or die". You can't grow more of it yourself either until late in the game[[note]](producing more algae involves ranching Puffs, collecting [[SolidGoldPoop the slime they excrete]], then refining that slime into more algae, but by the point you can safely and reliably do that you [[BraggingRightsReward probably don't need it anymore]])[[/note]] for extra irritation points.

** Just algae in general until you can get the relatively late game upgrades that make it obsolete. One Let's Player described the game as "find algae, or die". You can't grow more of it yourself either for extra irritation points.

** Steam geysers make water troubles a non-issue. While the water they put out is significantly hot, encasing them in insolated tiles or pumping the water to an insolated room just outside of your base negates the problem pretty handily. Bottled water doesn't heat things up too much, so the dups using it for that purpose isn't a problem and pumping the water to an oxygen producing room isn't a worry, as Electrolyzers always put out Oxygen at a fixed tempature regardless of the water pumped in, making cooling the oxygen the only real problem. Many people have managed to make fully self-sustaining colonies simply via steam geysers alone.

* GameBreaker: Finding a 'cold' biome early on can seriously help deal with a large number of problems a player would deal with otherwise; the low temperatures are great for killing a number of germs, making them ideal for storing food, they're a great place to set up a lot of machinery since the cold temperatures keep a large number of them from overheating and setting up an oxygen producing room in there does wonders for keeping temperatures in the base balanced out. Normally it's balanced out by the fact that world gen usually spawns them far away from the starting area (usually behind [[ThatOneLevel Swamp biomes]]) but every now and then, you'll get a lucky world gen that spawns one not far off from the main base.

** The inability to take direct command of the duplicants for tasks can get really bothersome. Even if you bump the priority of something up to the max nine and directly move the duplicant to what you want them to do, there's no guarantee they'll ''actually do it''. For building base walls and the like it's usually fine. For smaller but necessary tasks like farming or cleaning the outhouses? Expect the colony to die of starvation because no one wanted to farm, or duplicants peeing in the fresh water supply because nobody wanted to clean the outhouse. This is especially bad if a duplicant traps themselves in some way; even when in red alert mode, you can expect the duplicants to prioritize painting pictures, restocking cole generators and building stations instead of digging the trapped duplicant out until it's too late.

** How stress increases can seem extremely arbitrary, especially when duplicants seemingly have a stress jump for no reason and absolutely ''refuse'' to use a message bed even if you assign them to it and set the priority to the max.

** In any given run, you're likely to come across at least ''one'' duplicant who seems to make a habit out of causing trouble; be it getting himself locked out of the base/trapped while building something, refusing to use the bathroom even if you have multiples open until it's too late or refusing to take a break at the message bed when their stress starts getting high. Naturally, these duplicants will quickly start to grate on you as time goes by.
* ThatOneLevel: Swamp biomes. Extremely populated with germs and duplicants are almost guaranteed to get slimelung from it, which can kill them if not dealt with quickly and can very easily spread through the colony like wildfire. What makes it so hard though is the fact that swamp biomes like to generate right next to the base; sometimes completely engulfing it from all sides, which makes it impossible to avoid.

* TheScrappy: Any duplicants with Destructive as their negative trait can become this very quickly if the stress levels in your colony get too high. Expect a whirlwind of desperate rebuilding as they [[TooDumbToLive throw a tantrum and kick apart all the tech that's just barely keeping them alive.]]

** The random rescource allocation can increase or decrease a game's difficulty hugely, especially early on. Landed in a spot with no algae and don't have enough oxygen to mine out far enough to get more? [[FakeDifficulty Just give up and start a new colony.]] Not so bad later in the game where your tech can solve problems like this (i.e. making oxygen with just water) but in early game it's a killer.

** The germ system from the Outbreak upgrade.

* ScrappyMechanic: The germ system from the Outbreak upgrade.

* TheScrappy: Any duplicants with Destructive as their negative trait can become this very quickly if the stress levels in your colony get too high. Expect a whirlwind of desperate rebuilding as they [[TooDumbToLive throw a tantrum and kick apart all the tech just barely keeping them alive.]]

* TheScrappy: Any duplicants with Destructive as their negative trait can become this very quickly if the stress levels in your colony get too high. Expect a whirlwind of desperate rebuilding as they [[TooDumbToLive throw a tantrum and kick apart all the tech keeping them alive.]]