Build desktop apps and games in HTML/CSS/JS with 3D, physics, audio, and on-device AI wired into javascript, in one native process. QuickJS, a custom layout engine, Skia, and OpenGL. Windows, Mac, and Linux.
** this is pre-alpha **
Two familiar yardsticks, plus one that doesn't have a name yet:
- Rendering parity with Chromium (HTML/CSS). The app layer should look right.
- Feature parity with Godot's engine (no editor). 3D, physics, audio, the game runtime.
- On-device generation and perception as a native engine subsystem. Every modality the engine renders, it can also generate and understand, locally.
broworkshop houses the apps built with bro used to demonstrate the functionality.
bro broworkshop/bro.json
The launcher and a curated set of starter apps live in the sibling broworkshop repo: games, tools, demos, and AI/research apps you can clone and reshape for your own thing. bro is the runtime; the workshop is where the patterns are worked out.
Coding agents build web UIs really well. While they can build native UIs, in my experience, there's a lot more debugging happening to get something working. Electron solves that, but only for what the web platform natively supports.
In bro, HTML/CSS/JS is the UI/app layer like Electron but the rendering pipeline is ours, which means we can plug in whatever we want underneath. And we have: a 3D scene graph, Jolt physics, a real-time audio engine, mesh generation and CSG, navmesh pathfinding, game networking over GNS, native file dialogs, menu bars. All exposed to JS, all running in one process, no IPC to a Chromium renderer.
None of this is new, it's just a reconfiguration that works better for coding agents.
<!-- hello/index.html -->
<h1 id="msg">Hello</h1>
<button id="btn">Click me</button>
<script>
document.getElementById('btn').addEventListener('click', () => {
document.getElementById('msg').textContent = 'Hello, bro';
});
</script>bro path/to/helloSee broworkshop for example applications.
The app layer. Write the UI the way you already do. HTML5, CSS (flexbox, grid, gradients, border radius, overflow/scroll), SVG, Canvas 2D, WebGL 2.0, Web Components with Shadow DOM, Web Workers, Fetch, localStorage, form controls with real text editing. Text is shaped by HarfBuzz with bidi reordering, so ligatures, cursive joining, and RTL come out right. three.js and jQuery just work, and your web knowledge (and your coding agent's) transfers.
Beyond the web. Reachable from the same JS, one process, no IPC:
| Reach for | to |
|---|---|
bro.scene |
3D scene graph: meshes, sprites, particles, PBR lighting, skinned characters |
scene.createTerrain · createClipmapTerrain · createTileWorld · bro.worldgen |
chunked height-field terrain, camera-centred clipmaps, square/hex tile grids, learned elevation |
Physics / physics nodes |
Jolt rigid bodies, contact events, constraints, raycasts, characters, vehicles |
AudioContext (broaudio) |
real-time audio: synthesis, effects, spatial, MIDI |
bro.mesh · bro.ai.game · bro.net |
mesh generation + CSG · navmesh + A* pathfinding · game networking (GNS) |
<video> · VideoEncoder · GifEncoder |
WebM/VP9 playback, and encoding RGBA frames back out to a file |
native dialogs · menu bars · gizmos · multi-window · bro.steam |
OS-native app chrome and Steamworks integration |
On-device AI. Every modality above, the engine can also generate and perceive, locally, on the GPU, in the frame loop. No API key, no network, runs offline. bro.gpu probes the live CUDA/Metal/CPU backend.
| Reach for | to |
|---|---|
bro.lm |
generate & understand text (local LLMs: Qwen3, Qwen3.5, Mistral) |
bro.diffusion · bro.vision |
generate images (U-Net/VAE, LoRA) · perceive them (SAM, depth, normals, matting, ControlNet) |
bro.triposplat · bro.motion |
generate 3D from a single image · generate animation from text |
bro.tts · bro.stt · bro.diar |
speak (Kokoro, Qwen3-TTS) · hear (Whisper, Parakeet, Qwen3-ASR) · separate speakers |
bro.wake · bro.kws · bro.mic · bro.sense · bro.gesture · bro.listen |
wake words, keyword spotting, live mic, model-free acoustic sensors, gestures, concurrent streams |
bro.tensor · bro.image · bro.rave |
the tensor + image-kernel substrate underneath them all, plus neural audio encode/decode |
The left-hand bro.* names are the whole surface. Each has an annotated JSDoc reference in docs/ (read the .js files, not the source).
For development. Headless mode runs the full pipeline (GPU, real fonts, WebGL) without a window, driven by JS with virtual time for deterministic testing. See docs/headless.md. Line-coverage reports via OpenCppCoverage are wired up for bro and every sibling, pwsh scripts/coverage.ps1 in any repo. See docs/coverage.md.
- QuickJS. JavaScript engine (ES2020+).
- bromath. Header-only C++20 math: Vec/Quat/Mat, Color, AABB, easing curves. Used transitively by most siblings. See bromath.
- qjsbind. Header-only C++20 binding library for exposing C++ classes/functions to QuickJS with automatic type conversion. See qjsbind.
- brokit. Web-standard and system APIs (fetch, streams, storage, fs, crypto, events, and more). See brokit.
- htmlayout. HTML5 parsing (gumbo), CSS parsing, selector matching, style cascade, and block/inline/flex layout. See htmlayout.
- broaudio. Real-time audio engine. See broaudio.
- bromesh. Mesh generation, manipulation, analysis, and I/O. See bromesh.
- broflora. Ecosystem simulation (Makowski et al. "Synthetic Silviculture"): plants, foliage, blooms. See broflora.
- brotensor. Tensor type and device-neutral ops including a full training surface; CPU backend always built, CUDA/Metal additive and opt-in. Underpins brogameagent, brolm, brodiffusion, brosoundml, and brovisionml. See brotensor.
- brogameagent. Game AI: navmesh, A* pathfinding, steering, perception. See brogameagent.
- brolm. Language/text-model inference: BPE + Unigram tokenizers, transformer text encoders (CLIP, T5), CLIP vision encoder + scorer, and GGUF/safetensors LLMs. The text frontend brodiffusion builds on. See brolm.
- brodiffusion. Diffusion-model text-to-image inference: U-Net + VAE, DDIM/LCM schedulers, LoRA, INT8. See brodiffusion.
- brosoundml. Audio-ML model inference (TTS, STT, diarization, neural codec, wake) built on brotensor's FP32 audio op family. See brosoundml.
- brovisionml. Vision-model inference: SAM segmentation, Depth-Anything-V2 depth, DSINE surface normals, BiRefNet matting, and the ControlNet conditioning annotators (HED, lineart, MLSD, OpenPose, SegFormer). See brovisionml.
- broimage. Image decode/encode (stb) plus composable kernels (reduce/map/combine/lookup/stencil/resample/gradient), geometric ops, alpha-correct compositing, color/HSV/sRGB, normalization presets, and NHWC/NCHW preproc. Backs
bro.imageand host-side preprocessing in brolm/brodiffusion. See broimage. - Jolt Physics. Rigid body physics with contact listeners, integrated into the scene graph.
- Skia. 2D rasterization (text, paths, images, gradients). HTML/CSS is rasterized to a texture via Skia's Ganesh GL backend, with a CPU raster fallback for
--no-gpuheadless runs. Text runs through HarfBuzz shaping and Skia's UAX#9 bidi subset, both compiled from the Skia source bundle and on in every build profile, so ligatures, cursive joining, and RTL reordering are the one text path rather than an optional upgrade. - SDL3. Windowing, input events, and OpenGL contexts. All GPU work is OpenGL 3.3 Core (via glad) on SDL_GL contexts; there is no SDL_GPU, D3D12, or Metal path. The Skia-rasterized UI texture (Ganesh-GL) and the 3D scene layer are composited together as textured quads in the main GL context.
Also uses GameNetworkingSockets (Valve's GNS, via vcpkg), glad (OpenGL 3.3 Core loader), and FastNoise2 (via brokit).
C++20, roughly 183K lines under src/ with the JS bindings in src/js/ making up about half of it. Three executables over one Engine: bro (windowed), bro-headless (headless JS scripting and testing), and bro-server (dedicated game server, a fixed-tickrate JS loop with net, physics, mesh and noise, no window or renderer). See docs/multi-repo-workflow.md for development across the sibling repos.
See BUILDING.md for prerequisites, Skia setup, and build commands across Windows, Linux, and macOS. The build is modular: -DBRO_PROFILE=minimal|app|full picks a feature tier and individual -DBRO_WITH_* flags override it, with compiled-out features installing { available: false } JS stubs. See docs/build-options.md.
Double-clicking bro (or running it with no arguments) opens the project manager: a built-in home screen for creating new projects from skeletons, opening existing project folders, and drag-and-drop importing folders or .zip files. Project paths are persisted to a per-user registry (%APPDATA%/bro/projects.json on Windows, ~/Library/Application Support/bro/projects.json on macOS, ~/.local/share/bro/projects.json on Linux). See docs/projects.md.
To run a specific app directly, pass its path:
# Windows
./build/Release/bro.exe ../broworkshop/bro.json
# Linux / macOS
./build-release/bro ../broworkshop/bro.jsonLoads the app's index.html, applies stylesheets, executes scripts, and opens a window.
bro-headless ../broworkshop/demos/example # interactive REPL
bro-headless ../broworkshop/demos/example test.js # script file
bro-headless ../broworkshop/demos/example -e "document.querySelector('#btn').click()"
bro-headless --no-gpu ../broworkshop/demos/example # CPU-only (CI)Headless globals: screenshot(path), advanceTime(ms), flush(), sleep(ms), assert(cond, msg?).
See docs/headless.md for full documentation.
An app is a directory containing at minimum an index.html:
myapp/
index.html # required
style.css # linked via <link rel="stylesheet">
app.js # loaded via <script src="...">
For more elaborate setups, such as multiple apps under a project root with shared lib/ and system/ directories, see broworkshop for the layout pattern (project-level bro.json with default_app, lib, system).
Annotated .js files in docs/. Load them in your editor for JSDoc on every binding:
Graphics & world. scene-api.js, animation-api.js, lighting-api.js, mesh-api.js, terrain-api.js, clipmap-api.js, tile-api.js, worldgen-api.js, flora-api.js, physics-api.js, gizmo-api.js, math-api.js, noise-api.js.
Web & app surface. brokit-api.js, worker-api.js, iframe-api.js, window-api.js, matchmedia-api.js, web-animations-api.js, pointer-api.js, gamepad-api.js, time-api.js, menu-api.js, dialogs-api.js, image-api.js, imagebitmap-api.js, video-api.js, audio-api.js, net-api.js, net-sync-api.js.
On-device AI. gpu-api.js, tensor-api.js, lm-api.js, diffusion-api.js, vision-api.js, triposplat-api.js, motion-api.js, tts-api.js, stt-api.js, diar-api.js, rave-api.js, wake-api.js, kws-api.js, mic-api.js, sense-api.js, gesture-api.js, listen-api.js, ai-game-api.js.
Plus settings.md (settings + action binding), inspect.md (DOM inspector, very useful in headless), system-panels.md (authoring/overriding engine-level UI panels: menu bar, preferences modal, splash, inspector), projects.md (the project manager and skeletons), and build-options.md (profiles and feature flags).
while you technically could easily wire this up to be an actual web browser, it was not built for that. i have not paid mind to security at all. this exposes a lot more of your system to javascript than a browser does. it'd be better if we didn't run random internet code in this unsecured sandbox.
splitting the codebase exploration into chunks makes coding agents work better for my workflow. i'll try to keep setup reasonable but i expect the submodule list will continue to grow.
Third-party dependencies are under their own permissive licenses (MIT, BSD-3-Clause, zlib, Apache-2.0). See each library's LICENSE file in third_party/ or its respective repository.