1
Squirrel's Pick Squirrel's PickThe best game on this page. If you only try one, try this. Closest Match Closest MatchThe most similar game to the anchor, by what players say.
City BuilderRTSBase-Building
Strong Mods Strong ModsA deep, active modding scene extends it past its base content.
$9.79 ~115.2 hr median co-op complexity: moderate 85.3% of 68k
The Squirrel's verdictNorthgard trades card-driven tableau building for real-time territory control and clan management, adding co-op that Terraforming Mars lacks. The update track record is comparable: reviewers report post-update freezes, AI balance complaints, and bugs introduced alongside new DLC clans. At $9.79 and 115 hours median playtime, it suits players who want a longer strategic loop with territorial and combat decisions.
Not for you if you want turn-based card synergies and no real-time combat, or persistent post-update bugs and AI cheating complaints are dealbreakers.
2
Life SimAmericaArtificial Intelligence
~23.1 hr median no co-op complexity: light 77.9% of 848
The Squirrel's verdictTerraforming Mars rewards building production chains and converting resources into engine growth. My Gaming Club keeps that resource-conversion core but drops the competitive card drafting for a solo business sim: you build PCs, price goods, and grow a gaming club instead of a planet. Best for players who want economic engine-building without opponents or turn structure.
Not for you if you need turn-based multiplayer strategy instead of a real-time solo business sim that reviewers say runs poorly and requires heavy grinding for progress
3
Brass: Birmingham
PCMacLinux
Board GameTabletopTurn-Based Tactics
~15 hr median no co-op complexity: heavy 58.9% of 661
The Squirrel's verdictBoth are digital ports of acclaimed economic board games where the tabletop rules are more trusted than the app layer. Brass: Birmingham's difference is scope of failure: reviews report online multiplayer largely non-functional rather than just buggy, leaving it as a single-player AI trainer for people who already know the physical game.
Not for you if you want to play against other people online rather than practice solo against a weak, predictable AI.
4
ServiceIT: You can do IT
PC
ElectronicEducationJob Simulator
$7.14 ~7.4 hr median no co-op complexity: light 58% of 696
The Squirrel's verdictServiceIT suits players who enjoy learning dense interlocking systems at their own pace rather than competing against others. It's a solo IT-technician sim covering network diagnostics, soldering, and a course-based skill tree — no cards, no opponents, no co-op. Steam rating is Mixed at 58% positive, median playtime is 7.4 hours, priced at $7.14.
Not for you if you came for multiplayer strategy and card-based competition rather than a solo simulation of diagnosing and repairing hardware.
5
Life SimCharacter CustomizationOpen World
~8.3 hr median no co-op complexity: light 57% of 637
The Squirrel's verdictPlayers who find Terraforming Mars too dense and want something open-ended and low-stakes might try Live the Life, a solo sandbox where you furnish an apartment, work jobs, and shop for clothes. There is no card economy, no resource engine, and no opponents. Steam rating is Mixed at 57%, median playtime is 8.3 hours, and reviewers note slow development progress since its 2020 release.
Not for you if you want strategic resource management and card synergies — this is a mechanically thin life simulation with no competitive or engine-building structure.
6
Music
$14.99 ~50.8 hr median no co-op complexity: moderate 46.1% of 178
The Squirrel's verdictMusic Wars Empire is a music-industry management sim where you build bands, customize artists, and navigate a large-scale industry model — no card economy, no resource-track terraforming. There is no tutorial, mechanics require self-discovery, and a Mixed rating at 46% positive reflects persistent bugs and crashes that reviewers say have gone unaddressed. No co-op, PC only, 50.8 hours median playtime at $14.99.
Not for you if you need a stable, polished ruleset — reviewers describe crashes, broken mechanics, and a game that feels unfinished after years of release.
7
ActionAdventureLife Sim
Free ~0.8 hr median co-op complexity: light 37.7% of 3k
The Squirrel's verdictThe review pool for Greed of Man is almost entirely joke posts and copypasta, with no accounts of card mechanics, resource tracks, or turn structure to compare against Terraforming Mars. What's confirmed: it's free, supports co-op, released in 2023, and holds a Mostly Negative rating with a median playtime of 0.8 hours.
Not for you if you want confirmation the game's mechanics resemble Terraforming Mars, since the reviews describe none of them and most players log under an hour.
8
Space SimStrategy RPGExploration
$24.99 ~14.8 hr median no co-op complexity: moderate 37.1% of 477
The Squirrel's verdictBase One shares Terraforming Mars' emphasis on resource management and solo play (no co-op), but swaps card-driven engine building for real-time colony construction: assign crew, build modules, keep supplies flowing on a space station. Steam rating is Mostly Negative, median playtime 14.8 hours, priced $24.99, released 2021.
Not for you if you want a functional strategy loop — reviewers report crew pathfinding bugs that stall missions and a Mostly Negative rating.