In its fiction, RimWorld draws a lot from Firefly. This is where it gets its subtle Western vibe - frontier living, an arid environment, sparse law enforcement, and the constant threat of outlaws. We're also heavily inspired by science fiction novels like Dune and Alastair Reynolds' Revelation Space series (which both Alistair Lindsay and I are huge fans of). The Warhammer 40,000 universe also forms part of our inspiration.

In terms of game design, the game draws most from the 800-pound gorrilla of the simulation genre, Dwarf Fortress. We also take ideas from indie hits like FTL (our semi-random event format) and Prison Architect (its way of presenting a complex world in a comprehensible, interactable way). And, there are many others.

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.

Each character has a background that affects how they play. 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.

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.

Over the course of long games, players develop a motley group of refugees, pirate raiders, purchased slaves, and crashlanded survivors. The diversity of people makes each colony unique.

Ludeon Studios reveals RimWorld - Biotech as the third expansion to its sci-fi colony sim, coming later this month.

Biotech is focused around three major features:

• Control mechanoids, including many new mechanoid types, by making your colonist into a mechanitor
• Raise babies and children. Reproduce and create families - by both natural and artificial means
• Genetically-modify children and adults, and interact with new gene-modded factions

Children and reproduction

Now you can raise a family and tell your story for generations to come!

With Biotech, colonists (and outsiders) can become pregnant and give birth. Pregnancy can begin naturally, or via technological means, and can be controlled by a variety of methods.

Babies bring joy, but also challenges. Colonists’ hearts will melt when the baby coos and giggles in their arms. But it takes effort to keep a baby happy and healthy and loved - create a safe haven for them in a cozy pastel nursery where there is always warm milk, a comfortable crib, overflowing toy chests and kind caregivers.

They grow up fast (especially if you use a growth vat) - soon your child will be walking, talking, and getting into trouble. They’ll soak up knowledge in the classroom and tag along with adults to watch them work. Kids find many ways to entertain themselves with art, exploring nature, playing with technology, and more. Teach them lessons and they’ll learn how to survive, cook, make friends, create art, build, craft, hunt, and fight. Watch as they grow up and make mistakes, lose loved ones, and survive hardships.

A rich childhood makes a capable adult. Every few years, you choose which traits and passions a child will develop. The better-raised a child is, with smarter education and more attention, the more choices you’ll have, and the better their chances are to become a happy and talented adult. Some colonies will sacrifice everything to give a child the best upbringing, while others will use growth vats to pump out cheap workers and soldiers. The choice is up to you.

The mechanitor

Build and control mechanoids by making your colonist into a mechanitor - a person with a special brain implant that lets them psychically command semi-living machines.

Create mechanoids by growing them inside high-tech gestator tanks. Command the original centipede, lancer, and scyther, plus a wide variety of new combat and labor mechanoids. Grow your swarm from a few small workers and fighters to a fearsome squadron of massive ultratech war machines and industrial behemoths.

Mechanoid laborers can manufacture goods, rescue and tend to your colonists, build and repair structures, sow and harvest crops, haul stuff, and more. They never get sick. They don’t freeze in the snow or get poisoned in toxic fallout. They don’t suffer mental breaks from long hours in dark mineshafts or filthy garbage yards.

Combat mechanoids are very diverse in form and function. Some are cheap swarmers that overwhelm the enemy with numbers. Others project shields over their allies, or roast enemies with beam weapons, or charge up for massive concrete-melting hellsphere attacks. Mechanoids wield melee claws and blades, sniper weapons, even flamethrowers. Depending on which mechanoids you command, your tactical options will vary dramatically.

Mechanoid infrastructure has a special price: Pollution. Left unfrozen, toxic wastepacks deteriorate and leak pollutants into the environment. Pollution makes living things sick. It poisons your colonists and pets. It blocks the sunlight with smog and irritates your colonists’ lungs. It triggers hibernating insects to emerge on the planet’s surface. Some areas of the planet are so polluted that only twisted, toxin-adapted variants of plants and animals can survive there. Pollution is a challenge that you can handle in a variety of ways - freezing, export (neighbors might not like this), adaptation, high-tech atomization.

Advance your mechanitor’s capabilities by acquiring ancient mechanoid technology. This means calling dangerous new super-mechanoids to attack, in order to defeat them and steal technology from their smoking corpses. There are three types of hyper-deadly commander mechs to fight, each with its own weapons and combat style. Be sure you’re ready before you call these machine beasts to attack. Learn enough, and some day, you may command them as your own.

Gene modding

You can genetically-modify people to create xenohumans - humans with exotic traits. Genetic modifications range from subtle personality traits and eye color to hulking furry bodies, glands for fire-breathing, rapid regeneration, and even immortality.

The world contains a new set of xenohuman types and factions, including unstoppable super soldiers, fur-covered animal-controlling arctic settlers, toxin-immune human bioweapons, fire-breathing horned desert imp-people, psychic-bonding concubines, and more. The darkest of them drink blood, live in shadows, and live forever.

You can make your own xenotypes from scratch, and build infrastructure in your colony to enhance your people. Curate a collection of exotic genes by purchasing them from traders, accepting them as quest rewards, or extracting them from your menagerie of xenohuman prisoners. You can harvest the genes from anyone and implant those genes into your colonists and prisoners. You can also recombine genes to make bizarre and advantageous mixes of traits for implantation. Experiment with gene extraction and recombination to build your colony of xenohumans!

Update 1.4

Update 1.4 is available now on the Steam unstable branch for public beta testing, and to give modders more time to update before release. (The main branch that most people play is unaffected and still on version 1.3 for now).

If you’d like to try 1.4, you can play on the Steam branch unstable. (To get access, go to your Steam library, right-click RimWorld and select "Properties", then select the BETAS tab and choose branch  unstable. Restart Steam if your game does not automatically update.)

See info on key features below (changelog at the end):

• Startup performance improvements: We spent months optimizing launch and game loading times. In our tests launching RimWorld and loading savegames are roughly 37% faster! On an example system, that’s a startup time improvement from 33 to 21 seconds. Loading a fresh savegame dropped from 7.9 to 4.6 seconds.
• Painting and color customization for walls, floors, furniture, and lights: Give your colony a custom look by painting the walls, floors, and furniture of your settlement any of a huge variety of colors using dye harvested from the tinctoria crop. Install a range of new colored carpets in your colonists’ living spaces. Set the mood with lamps that you can set to any color to create your romantic rouge bedroom or an eerie fluorescent laboratory. We expect screenshots to get even more wild thanks to this.
• Styles always available: You can now use all styles of all buildings, items, and floors and visually customize your colony even without Ideology active.
• Actually useful shelves that store lots of stuff: Fill your storerooms with shelves, which can now hold up to 3 stacks of most items. (Our testers were very excited with this one!) There is also a 1-tile mini-shelf. Shelves should help to keep your colony tidy and organized, and protect your items.
• Two new turret types: We added two new turret types. The foam turret spits firefoam to extinguish nearby blazes. The rocketswarm turret is a defensive launcher - when triggered, it blankets a wide area in a barrage of small missiles. It is excellent against large groups of weaker enemies, but only works when you press the button, for extra drama!
• Starting possessions: Depending on backstory, your starting colonists might come with their own possessions! Not only does it make it a bit easier to start with imperfect colonists, it also gives them a personal touch.
• Rot stink: Keep rotten corpses and meat away from your colonists. In addition to being disturbing to look at, decomposing tissue now releases rot stink gas. Colonists that are chronically exposed to rot stink may develop the new “lung rot” disease. Keep extra empty graves and garbage dumps available for times when you’re overwhelmed with bodies!
• More prisoners to trade, release, and interact with: In addition to all the prisoners you got before, now you’ll get a new class of prisoner who is unwaveringly loyal to their home. They can’t be recruited, but they can be sold, sent home for diplomatic benefits, used for gene extraction or blood farming in  Biotech, or used in rituals and enslaved in  Ideology. We did it this way because we wanted to make all the uses for prisoners besides recruitment more viable. Adding a new stream of unwaveringly loyal prisoners does that without destroying the population progression balance. They can be disabled in the storyteller settings.
• New mod manager UI: Managing your mods is really easy and smooth with the new UI. Mods are now visibly split into active and inactive lists. You can access your mod options directly from the manager screen. You can also save and load mod lists and mass unsubscribe to any outdated or disabled mods. Press CTRL + left click to select multiple mods and drag them around. Also, new art banners!
• New mod mismatch window: Mods are now displayed in three columns: added, missing, and shared. You can save your current mod list and load it later on.
• New options menu: We’ve organized the options menu into tabs. (Mods get their own tab!) It is much easier to navigate.
• Heat overlay: A togglable heat overlay on the map visually shows you how chilly or hot it is indoors and outdoors.
• Quest search bar: A search bar in the quests menu to help you sort through all your available, active, and historical quests.
• Tile inspector: Shows you the details of a specific tile when you hover over it and press the “alt” key.

Read the full 1.4 changelog here.

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.

RimWorld is a story generator. It’s designed to co-author tragic, twisted, and triumphant stories about imprisoned pirates, desperate colonists, starvation and survival. It works by controlling the “random” events that the world throws at you. Every thunderstorm, pirate raid, and traveling salesman is a card dealt into your story by the 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, and each one applies a different algorithm for generating random events. So if you want a different kind of story for your colony, you can just choose a different storyteller.

• 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.

It's not about winning and losing - it's about the drama, tragedy, and comedy that goes on in your colony.

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 each 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.

The flavor of RimWorld is a mix between hard sci-fi and the Old West. It's a rim world at the edge of the galaxy, 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 the 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.

RimWorld is available for PC (Steam), PS4 and Xbox One  for $34.99.