Yeah, Dwarf Fortress too, but at least Dwarf Fortress has an extensive, well-documented wiki. Cataclysm: Dark Days Ahead had a not-very-up-to-date wiki at one point, but then whoever maintained it had it go down at some point in the past year, and I’d say that the game has also been constantly updated and more-dramatically-rebalanced than Dwarf Fortress, so learning to how to play involves scouring Reddit, YouTube, and Discord to try to figure out what information is current. I think that the current recommended route on the subreddit to learn how to play is to watch recent YouTube videos of some streamers playing, which is…kinda nuts. It’s not uncommon that a question on the subreddit as to an authoritative answer on game mechanics is “go check the code”…

There are also some military sims I’ve played that are probably reasonably approachable to players who are familiar with the military hardware involved from prior to the game, but for players who aren’t, they’re probably in for a lot of reading and understanding mechanics, and some milsims don’t bother to document that, so you really need to do outside reading beyond whatever the game documentation has.