A sci fi colony sim driven by an intelligent AI storyteller.

RimWorld follows three survivors from a crashed space liner as they build a colony on a frontier world at the rim of the galaxy.

Inspired by the space western vibe of Firefly, the deep simulation of Dwarf Fortress, and the epic scale of Dune and Warhammer 40,000.

Manage colonists' moods, needs, thoughts, individual wounds, and illnesses. Engage in deeply-simulated small-team gunplay. Fashion structures, weapons, and apparel from metal, wood, stone, cloth, or exotic, futuristic materials. Fight pirate raiders, hostile tribes, rampaging animals and ancient killing machines. Discover a new generated world each time you play. Build colonies in biomes ranging from desert to jungle to tundra, each with unique flora and fauna. Manage and develop colonists with unique backstories, traits, and skills. Learn to play this deep game smoothly and naturally with our intelligent, reactive AI tutor.

For Windows, Mac, Linux. The game is distributed by DRM-free download. RimWorld is being created by Tynan Sylvester and Ludeon Studios. 9498 people pledged $268,132 on the RimWorld Kickstarter.

The AI Storyteller

I've always thought the best part of games like Dwarf Fortress and The Sims was the stories that come out of them. That's why RimWorld is designed as a story generator. It's not about winning and losing - it's about the drama, tragedy, and comedy that goes on in your colony.

To keep things interesting, the game creates events like pirate raids, trader arrivals, and storms. But these events aren't random. RimWorld uses an AI Storyteller (modeled after the AI Director from Left 4 Dead) who analyzes your situation and decides which event she thinks will make the best story. There are several storytellers to choose from:

  • Cassandra Classic aims to create a rising curve of tension over the course of the game. Early on, the most dangerous thing she'll do is send a psychotic squirrel after you. Later on, bands of scavengers will arrive. In the late game, look forward to combined-arms attacks from mercenaries mixed with lightning storms and crop blights. If you want a traditional tension and difficulty curve, go with Cassandra.
  • Phoebe Friendly is for the player who just wants to build and watch a colony grow. She'll occasionally create minor disasters, but nothing that would threaten the existence of the colony. If you want a more relaxing game about growth and success, choose Phoebe.
  • Randy Random follows no rules. He may give you some amazing stroke of luck, like a trader selling an advanced weapon for a low price or a group of helpful immigrants, followed by a near-unbeatable pirate attack combined with an electrical fire. If you think losing is fun, you might want to try Randy.

And we're considering other AI Storytellers, too. High population storytellers, starvation storytellers, seasonal storytellers, moody storytellers, and anything the community thinks up are all on the table.

A large, developed colony.
An well-developed colony at dawn. Click the image to zoom. Click here to zoom to the annotated version.

A motley crew

In RimWorld, your colonists are not professional settlers – they’re survivors from a crashed passenger liner. They'll be accountants, homemakers, journalists, cooks, nobles, urchins, and soldiers.

A nobleman will be great at social skills (for recruiting prisoners or negotiating trade prices), but refuse to do physical work. A farm oaf knows how to grow food, but cannot do research. A nerdy scientist is great at research, but cannot do social tasks at all. A genetically-engineered assassin can do nothing but kill – but he does that very well.

Each character has personality traits. Neurotic colonists work faster, but are more stressed and prone to mental breaks. Abrasive characters will interact poorly and harm the mood of those around them. A nudist loves to be naked, while a cannibal gets a rush from consuming human flesh.

You’ll acquire more colonists by taking in refugees, capturing people in combat and turning them to your side, buying them from slave traders, rescuing them, or taking in migrants.

A running battle with a large tribal raiding party.

Deep health modeling

Wounds are tracked on each body part and will affect a character's abilities. Eye injuries make it hard to shoot or do surgery. Wounded legs slow people down. Hands, brain, mouth, heart, liver, kidneys, stomach, feet, fingers, toes, and more can all be wounded, diseased, or missing, and all have logical in-game effects. And other species have their own body layouts - take off a deer's leg, and it can still run on the other three!

You can repair body parts with prosthetics ranging from primitive to transcendent. A peg leg will get Joe Colonist walking after an unfortunate incident with a rhinoceros, but he'll still be quite slow. Buy an expensive bionic leg from a trader the next year, and Joe becomes a superhuman runner. You can even extract, sell, buy, and transplant internal organs.

Diseases are a serious threat. Open wounds will get infected. Flu and plague can appear anywhere, and tropical rainforest areas are rife with malaria and sleeping sickness. As colonists age, they can develop chronic conditions like cataracts or bad backs.

A raider with malaria, a missing finger, a scar, and several wounds from melee weapons.

World generation and biomes

The game generates a whole planet from pole to equator. You choose whether to land your crash pods in a cold northern tundra, a parched desert plain, a temperate forest, or a steaming equatorial jungle.

Different areas have different animals, plants, diseases, temperatures, rainfall, mineral resources, and terrain. These challenges of surviving in a disease-infested, choking jungle are very different from those in a parched desert wasteland or a frozen tundra with a two-month growing season.

One of countless possible randomly-generated worlds.

Seasons and temperature modeling

Temperatures are modeled both outdoors and indoors. As the seasons turn, the outdoor temperatures will rise and fall. Plants only grow in some temperatures. When it gets cold, it will snow. People can get hypothermia or heatstroke.

You can control indoor temperatures with heaters and air conditioners to aid survival, comfort, prevent food from rotting. You can even build deadly temperature traps to cook enemies alive.

A tundra colony in mid-winter. Without food stored to survive winter, they'll have to turn to hydroponics, hunting, or cannibalism.

The tactics engine

RimWorld uses an engine that I originally developed to power a tactical combat sim similar to Jagged Alliance 2. This means it has a lot of features designed to make small-team firefights interesting. For example:

  • There's a cover system that models low cover and leaning around corners.
  • There's a really nuanced algorithm for determining and reporting hit chances based on distance, skill, weapon, lighting, angle, and cover.
  • Weapons have some pretty deep stats.
  • The AI plans and executes tactical moves like flanking while trying to stay out of the enemy's line of fire. It uses a number of heuristic algorithms to analyze the battlefield and use the space effectively. It works with allies and avoids bunching up.

I think most base-builder developers wouldn't put this much effort into a tactics engine, but having inherited from that earlier project, RimWorld benefits greatly in unexpected ways.

Because of how important cover and positioning are in gunfights, our combat interacts deeply with the colony's layout and structure. This means players have to think about how they want to position their constructions to maximum advantage in future firefights. Combat in general is a lot more interesting than the traditional trading of blows you might expect in a base-building game. And it's possible to build a wide variety of base configurations for maximum tactical advantage against diverse foes.

Raiders assault from the north. The colonists have fallen back from their frontline sandbag positions.

The teaching system

This kind of game can be really hard to learn. So we've created an adaptive teaching system that watches your actions to figure out which parts of the game you understand, and teaches the parts you're missing. If you don't understand a control, the game will notice and help you out unobtrusively. If you already know something, the game won't interrupt you.

RimWorld also uses a notification system to make sure you don't miss anything that needs looking at. If you're low on food, or a colonist is about to go berserk, a message hovers in the corner of the screen informing you of the fact. No more getting annihilated because you missed some little detail. If you get annihilated, it'll be for a totally legitimate reason.


People in RimWorld constantly observe their situation and surroundings in order to decide how to feel at any given moment. They respond to hunger and fatigue, witnessing death, disrespectfully unburied corpses, being wounded, being left in darkness, getting packed into cramped environments, sleeping outside or in the same room as others, and many other situations. You can inspect a character's psychology at any time to see what they're feeling and why.

When a colonist becomes too stressed, they may suffer a "mental break". Some will give up and wander the colony for a time. Some will leave. And some will, in dwarfish fashion, become psychotic and throw a violent tantrum.

Sheckley the miner thinks about a recent battle while rescuing a wounded friend.

The universe

The flavor of RimWorld is a mix between hard sci-fi and the Old West. It's a rim world at the edge of known space, far from the civilized core worlds. The planet is vast and mostly empty, and there are no strong civilizing authorities anywhere nearby. You're on your own.

The core idea in the RimWorld universe is diversity. In this setting, humanity is spread across the galaxy, yet lacks any way of traveling or communicating faster than light. Combined with the fact that stellar civilizations regress (due to war or plague) as often as they progress, this means that someone traveling between stars may end up interacting with people at any level of development, from pre-agricultural tribes to transcendent machine gods.

Your starting colonists in RimWorld are at a technological level in the middle of this span. But you may end up interacting with people at much lower and higher levels, as well as acquiring and using their tools and weapons. In RimWorld, a single fight can involve a bow and arrow, a revolver, a charged-shot pulse rifle, and a near-magical teleportation device.

A late-game colony.
A late-game colony.
A large northern colony in winter.
The same colony on a spring night.
75,000+ sold

No PayPal account needed. You can buy with a credit card through Stripe.

You can give RimWorld as a gift! Just buy it for yourself and email ludeonhelp@gmail.com with the receipient's email address. We'll redirect updates to them; you can give them the download link whenever you wish.

Full Game Pack ($30)

Instant access to the latest alpha version as well as all updates up to and including the final game.

Plus, get the Prototype Pack of five early game designs that eventually became RimWorld.

Name in Game Pack ($45)

Put a name (probably yours) into the game and appear as a pirate raider, colonist, traveler, or trader. Players will recruit, command, and fight you for all time! Includes the Full Game Pack.

Backstory in Game Pack ($125)

Like Name in Game, but you also get to write a unique character background, including backstories and skills.

Write yourself as an interplanetary detective, an entrepreneur, an ex-artist, or anything else you can think of! (Content must be fictionally coherent.)

Pirate King Pack ($200)

Like Backstory in Game, but your character will be a pirate leader who commands a group of raiders.

You can write a more intense, stronger character, and they'll play a key role. In “negotiations”, your character will be the pirate representative. Yarr!

Please note that player-created content must follow the creative rewards guidelines.

Tier upgrades

Want to upgrade to a higher tier? Just PayPal the price difference to ludeonstudios@gmail.com and email our support pro Michael from your PayPal email with the transaction ID. I'll have you upgraded right quick!


Includes community-made translations into: German, French, Italian, Spanish, Japanese, Chinese (simplified), Chinese (traditional), Danish, Dutch, Russian, Arabic, Czech, Estonian, Finnish, Hungarian, Korean, Norwegian, Polish, Portuguese, Portuguese (Brazilian), Romanian, Slovak, Swedish, Turkish, and Ukrainian.

© Ludeon Studios and Tynan Sylvester.
Memento mori.