RimWorld's biggest-ever expansion brings mech armies, gene-splicing, and bouncing babies

Everything going pear-shaped in Rimworld.
(Image credit: Ludeon Studios.)

Rimworld will shortly receive its third major expansion, called Biotech, and it's going all Crusader Kings on our ass. Biotech introduces three new features to the already pretty wonderful space colony simulator: controllable mechanoids, genetic modification, and good old human reproduction. Yep: time to make space babies.

Colonists (and for the adventurous, outsiders) can now become pregnant and give birth. How about this for a classic patch note: "Pregnancy can begin naturally, or via technological means, and can be controlled by a variety of methods."

Babies will make colonists happy, for the most part, but also mean a boatload of extra work. Players will have to build lovely safe nurseries for them, with plentiful food and constant care, or the babies will not be little bundles of joy. And they grow up fast, so soon need a classroom, and a lesson plan, and will begin tagging along with adults to learn about Rimworld's important skills.

Essentially, though, there's a moral choice. You don't have to give these babies a good life, rich in creative pursuits and emotionally rewarding. You might just want worker drones. "Every few years, you choose which traits and passions a child will develop," read the notes. "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 mechanoid side perhaps alleviates the need for such tactics, though is pretty dystopian itself. These mechs are semi-living machines that have been in Rimworld previously as an endgame challenge, but now players can control them with a specific brain implant, and essentially automate a bunch of jobs: manufacturing, caring for colonists, building and repair, farming, and fighting. The secret sauce with mechanoids of course is that, unlike your human colonists, they don't get angry or sad or depressed: they just do the work.

Bring on the mechanoid army! Oh wait. Mechanoids produce toxic wastepacks throughout their operation which, if not frozen, cause environmental pollution. Pollution poisons your colonists and animals, creates environmental smog, and triggers hibernating insects to wake (I'm guessing these insects are not nice). Players have various options for dealing with it, but go big on mechanoids and you'll basically also need a climate change policy.

Everything's on fire in Rimworld.

(Image credit: Ludeon Studios)

Family drama

"From the most classic novels of high culture to the bawdiest barroom tales, questions of family obligation, sacrifice, life and death, and relationships are central to our most compelling stories."

Tynan Sylvester

As if we weren't getting into the future hell of science fiction enough, Biotech also adds gene modding. You can now make your humans into xenohumans through modifications that "range from subtle personality traits and eye color to hulking furry bodies, glands for fire-breathing, rapid regeneration, and even immortality." Well, at least Sonic the Hedgehog fans will be happy.

The fun thing about all of this, and Rimworld as a whole, is that these new options don't just apply to you. The hostile worlds you build on will now have their own babies, mechanoids and xenohuman types, among which is apparently a "psychic-bonding concubine" faction.

Rimworld creator and developer Tynan Sylvester has written at some length about the design goals of the game more widely and what Biotech is looking to add. Rimworld is one of those games people describe as a 'story generator', because the fun is very much in that narrative of how your colony grows, adapts, deals with disaster, and ultimately how it ends. You can see why adding babies and the associated familial relationships into that dynamic makes sense.

"Family-linked drama is the bread and butter of stories across older media," says Sylvester. "From the most classic novels of high culture to the bawdiest barroom tales, questions of family obligation, sacrifice, life and death, and relationships are central to our most compelling stories. From 'No, I am your father,' to 'I will find you and I will kill you,' to 'You are the father,' family relationships are at the center of story. This is true in the western stories that RimWorld is inspired by as well.

"Extending that into RimWorld makes obvious sense and it’s something I’ve always been interested in. However, it took a long time to get here because these are such complex topics. Reproduction, birth, baby care and child raising all have a lot of fine details and rich content that I always knew would take substantial effort to get right. I wanted to make sure we had the development power to make the game generate these kinds of powerful family-oriented emotions without cutting corners or excessive jank."

The update is marked as 1.4 and is currently live on the unstable branch of the game (you can opt-in by right-clicking the game on Steam, selecting 'properties', then the unstable branch option in the 'Betas' tab), with the normal game remaining on 1.3 for a few weeks while the developers iron-out any bugs.

As well as Biotech there are some notable improvements: the devs have spent considerable time optimising the game's launch and load times, and now say it's "roughly 37% faster!" It adds paint and colour customisation so you can get your colony looking just right, it makes the previously weeny shelves "actually useful" for storage, new turret types, new starting possessions for colonists, increased sophistication of how corpses decompose… yep, it's that type of game.

Most impressive—and fair play for this—is the addition of a mod manager UI. Rimworld has an absolute boatload of mods, and this splits your mods into active and inactive lists, lets you save and load certain mod configurations, identifies outdated or disabled mods, and adds a mismatch window to alert players when they're missing something essential.

Biotech looks like the biggest and most impressive Rimworld expansion yet: and this is already a great game. There's so much in it, apparently, that the developers considered splitting it into two, but "decided to keep it all together as one extra-juicy expansion." You can play it now, or wait for the official release "within weeks."

Rich Stanton

Rich is a games journalist with 15 years' experience, beginning his career on Edge magazine before working for a wide range of outlets, including Ars Technica, Eurogamer, GamesRadar+, Gamespot, the Guardian, IGN, the New Statesman, Polygon, and Vice. He was the editor of Kotaku UK, the UK arm of Kotaku, for three years before joining PC Gamer. He is the author of a Brief History of Video Games, a full history of the medium, which the Midwest Book Review described as "[a] must-read for serious minded game historians and curious video game connoisseurs alike."