Oxygen Not Included occupies a similar space to Factorio and Rimworld in my list of all-time favourite games. All three are marvellous and near-impenetrable management games, oozing with character and complexity. The key difference is that in Oxygen Not Included, it's guaranteed that you'll spend at least some of your time expunging whole pints of urine from your base before it can seep into your last remaining water reservoir.
There is no guarantee that you'll succeed.
Oxygen Not Included is a disaster simulator at heart. You begin a game trapped inexplicably in the centre of an asteroid, flush with building materials, precious metals, and exploitable resources, but very much lacking in food and oxygen. Armed with nothing more than the ability to command your three extremely loyal but foolish starting clones (called dupes) to do your bidding, you must quickly explore and expand outwards, ensuring that your lowly dupes (and all future dupes that you print out with your central printing pod) have everything they need in order to survive. Including, and perhaps most especially, a corner they can sprint to whenever it's time to evacuate the literal gallons of waste they've somehow built up over the past few minutes of procrastinating.
ONI is far better at creating emergent stories than any other game I've played. As much as I adore Rimworld, there's no denying that its legendary emergent narrative engine runs largely on the fuel of its events system, which injects threat and drama into your colonists' lives from the external, from without. In Oxygen Not Included, the stories come from within. All the tales I've told my friends and family about my latest game of ONI came about entirely through my own exploration and interactions with the perilous jenga tower of disasters all around you.
There's far more to talk about with ONI than I am free to do here, so if this is your first look at Klei's magnificent management sim, I'd heartily encourage that you read Nate's excellent review of the game from last year. Or, if you have the game but you're struggling to pierce its thick, chitinous armour, you may want to check out my guide to surviving the first 30 cycles of Oxygen Not Included.