spiral@out:~/blog$ cat transmissions/brutal.md

BRUTAL: The Framework That Got RimWorld Off Unity

[2026-10-16] ::gamedev, csharp, vulkan, open-source, frameworks

DayZ creator Dean Hall has open-sourced BRUTAL, a C# framework for making games, or for making your own game engine. GamesIndustry.biz covered the announcement mostly through Hall's argument against Unity and Unreal. This post covers the rest: what's actually in the repo, how the licence works, and what it took to move RimWorld off Unity.

BRUTAL is developed by Ahwoo in collaboration with RocketWerkz, both of them Hall's Auckland companies. Work started in 2022, and it's free to use in commercial games with no royalties.

A framework, not an engine

The README is blunt about what BRUTAL isn't: "There is no editor, no scene graph and no renderer, and we're not adding them." The team says it will reject pull requests that try to grow it in that direction, because "adding everything is how the industry ended up with the kind of engines we don't want to use."

What you get instead is a foundation. The project compares it to the Linux kernel versus a distro like Ubuntu: BRUTAL handles the low-level layer and you build the game-specific systems on top. RocketWerkz built Kitten Space Agency directly on it. Ludeon Studios built a whole engine on it instead.

What's in the box

The core is Brutal.Interop, a custom interop layer that gives modern C# and .NET direct access to native APIs and C/C++ libraries. Around that sit 48 libraries, each its own NuGet package, so you reference only what you need:

  • Foundations: unmanaged memory and allocators, collections and string handling that don't allocate, vector and matrix maths, a job system, logging and localisation.
  • Graphics: Vulkan bindings plus the Vulkan Memory Allocator, OpenGL, shader compilation through ShaderC and Slang, and texture, KTX, glTF and mesh-optimisation loaders.
  • Windowing and UI: GLFW and SDL (with SDL's image, mixer and font add-ons), Dear ImGui on the docking branch, and ImPlot.
  • Everything else: Jolt and Box2D for 3D and 2D physics, FMOD and OpenAL for audio, RakNet for networking, RenderDoc capture integration, native file dialogs, and even NotCurses for terminal UIs.

The design goal running through all of it is what Hall calls an "obsessive focus on reducing allocations and unnecessary overhead." BRUTAL uses unmanaged memory and unsafe code wherever it makes sense, which keeps the .NET garbage collector out of the hot path.

The RimWorld test

The strongest argument for BRUTAL is RimWorld. On October 12, Ludeon announced update 1.7, which moves the game from Unity to Waylith, Ludeon's own engine, built with BRUTAL as its foundation. Ludeon's numbers:

  • 2 to 4 times better performance overall in their tests.
  • 2.2 times better on a stress-tested late-game colony compared with 1.6.
  • A 1,500-mod pack went from 14 minutes to 6 minutes to load.

The bigger achievement is what didn't break. Ludeon says the game looks and plays exactly the same, 1.6 saves load in 1.7 (and back again), and "the vast majority of mods work on 1.7 without any changes." For a game whose community runs thousands of mods, that's the hard part. Modders also get the latest C# language features. The one casualty: PCs more than about ten years old may not run 1.7. It's on Steam's unstable beta branch now.

Ludeon also says Waylith will power its next, unannounced game.

Built for a solar system at real scale

BRUTAL grew out of Kitten Space Agency, a free pre-alpha spaceflight sim that runs a solar system at real scale. A game like that needs to track a spacecraft precisely as it crosses interplanetary distances, then just as precisely as it docks with another ship, and general-purpose engines aren't built around that. BRUTAL let RocketWerkz design positions, coordinates and rendering around the simulation and dig into performance problems directly. KSA won Most Innovative Hi-Tech Creative Technology Solution at the 2026 NZ Hi-Tech Awards.

Felipe Falanghe, who created Kerbal Space Program, collaborates on KSA and is building his next game on BRUTAL too. "Coming from Unity to working in BRUTAL, initially it was a bit daunting," he said. "But once you're there, you own everything that you've created."

The README lists six projects so far: RimWorld via Waylith, plus Kitten Space Agency, Torpedia, Art of the Rail and Gruntz from RocketWerkz, and Afterskies from Floating Origin Interactive.

Trying it

You need the .NET 10 SDK, Windows or Linux, and a Vulkan 1.3 GPU if you're rendering. (Ahwoo's site lists macOS as a target too.) The README's hello-world just opens a window:

dotnet new console -n HelloBrutal
cd HelloBrutal
dotnet add package Ahwoo.Brutal.Core
dotnet add package Ahwoo.Brutal.Glfw
using Brutal.GlfwApi;
using Brutal.Numerics;

if (!Glfw.Init())
    throw new Exception("Failed to initialize GLFW");

Glfw.WindowHint(GlfwWindowHint.ClientApi, 0);
var window = Glfw.CreateWindow(new GlfwWindow.CreateInfo
{
    Title = "Hello BRUTAL",
    Size = new int2(1280, 720),
});

while (!window.ShouldClose)
    Glfw.PollEvents();

Glfw.Terminate();

That's a window with no graphics API attached. Everything after that is up to you: add the Vulkan packages to write a renderer, ImGui for debug UI, the job system for parallelism, FMOD and RakNet for audio and networking.

The licence, read closely

Headlines say BRUTAL only asks for a credits line. The actual licence asks for a little more. It's MIT-based with an attribution clause, and a game built with it has to:

  1. include the BRUTAL copyright notice in its credits screen or equivalent,
  2. show the BRUTAL logo before gameplay starts, and
  3. ship NOTICE.txt with the product.

The logo requirement is waived for non-profit projects, and Ahwoo will arrange a separate commercial licence if you don't want to show it. The licence isn't OSI-approved yet. The team says it simply hasn't submitted it, and plans to refine it with community feedback.

The fine print

  • The name is a warning. "We called it BRUTAL because it can be brutal to use at times," says Ahwoo's head of engineering, Rian Drake. "There are no guardrails." It's aimed at experienced programmers who want to make their own architecture decisions.
  • It's a day-one open-source project. The repo has no build scripts, project files or solution yet, so for now you use the NuGet packages and read or fork the source. Early forum posts also pointed out that the linked API docs weren't public at launch.
  • Contributions are scoped tightly. Commits need a sign-off, AI-assisted contributions have their own rules, and anything that drifts from the "few low-level things done well" mission gets turned away.

Why Hall did it

Part of the motivation is personal. In May 2025, Unity sent RocketWerkz a notice threatening to revoke its licences, and Hall said the evidence included two people who had never worked there. He told PC Gamer the episode confirmed the studio's existing move away from Unity for new projects.

The broader argument is about dependence. Hall told GamesIndustry.biz he worries that as AI coding tools erode software companies' competitive moats, engine vendors will try to squeeze more out of developers who feel they can't leave, "whether through royalties, subscriptions, or more restrictive licensing." He's careful not to tell anyone to drop Unity or Unreal tomorrow: "For many projects, they're absolutely the right choice." The point is having a way out. The README puts it in one line: "You are only as independent as your tools are."

He also expects more frameworks like BRUTAL to appear as the cost of building alternatives falls, and he's given his own an exit hatch: "If one day we stop being accountable to developers ourselves, they should have the ability to fork the framework and go their own way."

Who it's for

BRUTAL isn't the place to make your first game. It's for teams whose game doesn't fit a general-purpose engine, like real-scale simulations or colony sims with thousands of mods, and for studios that want to own their technology all the way down. RimWorld showed a successful game can make that move without breaking its community. If your game is hard to make, BRUTAL is worth a look.

The GitHub repo, the BRUTAL site and the forums are the places to start, and it's in the resource index now.

End of transmission.

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