Dwarf Fortress
A suitable starting point is a game that greatly influenced RimWorld (along with Dune, Firefly and Warhammer 40,000). Dwarf Fortress' deep simulation system is so deep that's its Steam release date is currently slated as "time is subjective." With that said, the game is available to play on PC, Mac, and Linux.
There are two main gameplay modes: Fortress and Adventurer. The seemingly limitless meat of the game is in Fortress mode, commanding dwarves as they search for wealth in their procedurally generated mountain. The dwarves sustain themselves on the staples: food and beer; and they'll need to protect themselves from hostile outsiders. The game will soon expand, allowing players to craft items, build structures, and grow the culture of dwarven society (bookbinding, anyone?). In Adventurer mode, you create a character, choose both functional and physical attributes, and select their skills. This character is part of the same worlds created in Fortress mode, which continues to pass time and develop. Eating, drinking, and sleeping are vital tasks, as well as sheltering from evil creatures of the night. Adventurer mode also includes a quest system that the NPCs provide via rumors and agreements. And, of course, since time is subjective, players can review the history of the worlds and characters created in Legends mode.
Cities Skylines
Harkening back to a certain wildly popular simulation city builder of the 1990s (or was it 2000?), City: Skylines provides an updated feel for a new generation ready to get lost in the immersion of creating a city from the ground up. The player assumes the role of city mayor, overseeing transportation, economics, healthcare, education, and more. The citizens will be judging the mayors choices, so try to keep that in mind. Included in the After Dark expansion, a day and night cycle is introduced which adds nuance to what goes on—or doesn't—after dark. Another expansion, Snowfall, includes an in-game weather system. Managing the dynamic of changing seasons is sure to test your mayoral prowess.
Prison Architect
Take on the role of warden as you build and manage a high-security prison in Prison Architect. There's a lot on the to-do list including money management, natural disaster preparation, riot prevention, and—everyone's favorite—litigation! Ethics come into play, so ensuring the staff is trained to serve, protect...and snitch is vital for prosperity. The inmates, however, need the most work (obviously), and providing specific treatment plans and duties to reform them is also part of the warden's to-do list. The game includes an Escape Mode, wherein the player attempts to break out of their own maximum-security prison. There's also an Online Mode with over 12,000 prisons from wardens across the world to explore.
Factorio
Prepare to clock in early to get as many hours as possible (some playtimes range from hundreds to thousands of hours on Steam) in this addicting factory builder. At the outset, simple tasks include tree chopping, ore mining, and mechanical crafting. Soon thereafter, the industrial revolution will be in full force as a small venture becomes a mechanized powerhouse. The modding capabilities in Factorio are also vast in number: should the provided maps and scenarios not suffice, there's the option to build or venture into other player's designs. Factorio is a pure management sim that has the possibility of immersing a person for days, months, years...and most players don't seem to want to clock out anytime soon.
DRAGON QUEST BUILDERS 2
Don't let the "2" deter you, DRAGON QUEST BUILDERS 2 is a block-building RPG sequel in name only. New characters, a huge world, nearly infinite building options, and a storyline that is very Square-Enix. The Children of Hargon imprisoned all the world's builders in an attempt to stop building, cooking, and even creating things. (Which begs the question: what do these kids do all day?) Luckily, the avatar managed to escape capture. Washed ashore on an island, the avatar is tasked with exploring, building, and defending the newly built towns from foes. Beyond the single-player campaign, there's a full multiplayer building mode to collaborate with others online.
Stardew Valley
Fed up with the monotony of the daily grind, you receive a letter that changes everything: you've inherited a plot of farmland from your grandfather! While it's definitely a fixer-upper, the farm will soon grow with the addition of crops and livestock. There are plenty of activities off the farm, too, including fishing, home design, and spelunking. The caves in Stardew Valley are deep and mysterious, with monsters and treasure (risk and reward) inhabiting the underground network. During downtime, tackle the similarly deep and mysterious realm of dating with 12 townsfolk you can court and possibly start a family with (extra farmhands, anyone?). ConcernedApe, the developer, has continuously updated the game throughout the years. A recent update included local (split-screen) co-op, a new island, a new farm layout, and much more that doesn't deserve spoiling.
Two Point Hospital
Remember Theme Hospital? Two Point Hospital is a sequel of sorts to the 1997 game with an addictive mix of management and oddity. With no shortage of humor, design ideal hospitals to care for the good—and seemingly deeply plagued—people of Two Point County. Diagnose, treat, and cure ailments including premature mummification and room-clearing brain farts. The game ramps up progression with aplomb from a small clinic to a fully functioning multi-building enterprise. As hospitals spring up across the county, the option to return and perfect prior endeavors is a welcome addition for those seeking three-star rankings.
Townscaper
Build a house or a replica of the Tower of Pisa in this simulation game that leans more in the creative toy specification with its lack of goals and rules. That said, there's building aplenty and gorgeous cityscapes just a few simple actions away. Choose colors, place blocks along the grid, and—depending on your placements—watch those blocks morph into homes, villages, and cities reaching the sky or the horizon or...really anywhere; it's a sandbox game, after all. Since there is no goal besides adding and removing blocks, relax and enjoy the experience—no one's going to judge if your Golden Gate Bridge looks more like a troll's crosswalk.
Fallout Shelter
Bethesda's first venture in free to play expanded on the ever-mysterious—and seemingly limitless—world of vaults in the Fallout universe. Take the role of Overseer and guide your vault to prosperity, all while keeping it safe from external harm (hello, Deathclaw tower defense). Dwellers possess unique characteristics, so identify their ideal role in the community and supplement with training, weapons, and outfits. Worthless junk becomes useful items with crafting, and single dwellers couple up to create...yes, more dwellers to contribute to the vault. Explore the wasteland for items, experience, and Caps. In this post-nuclear vault, you're not assistant to the regional manager, you ARE the manager; try to keep everyone alive.
Garden Story
Garden Story is more The Grapes of Task With a Li'l Wrath in this cozy simulator/Action-RPG. As Concord, a young grape resident, restore The Grove by exploring locations infested by Rot, building up your community and solving puzzles along the way. After dungeon crawling, explore the world and foster trust among residents to rebuild the island. Along the way, gathering materials, curating libraries, upgrading tools, and rebuilding structures is vital in reviving The Grove's ecosystem. With a sweet soundtrack, a host of colorful fruits and vegetables, and some mild (read: not spicy) dungeon-crawling combat, Garden Story is a quaint blend of adventure and maintenance.
