gasm

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gasmWrite a game once. Run it everywhere.

Games compile to one WebAssembly file. Small native and browser runners give them a stable interface for graphics, sound, input and networking.

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How it works
gasm

One artifact

A game is a single .wasm file. The same bytes run in a native window (wasmtime + wgpu), in any WebGPU browser, and headless in Node for CI.

A small, stable ABI

A small core (video, audio, input, assets, params), plus optional GPU, network and storage modules. A new runner is weeks of work, not years.

3D via WebGPU or OpenGL ES

gasm:gfx is a compact WebGPU subset with WGSL shaders; natively it runs on Metal, Vulkan and D3D12 through wgpu. gasm:gl is OpenGL ES 3.0 with WebGL 2's rules for existing GL code (browser and headless for now).

Online multiplayer

gasm:net gives every runner WebSocket-style messaging. The sumo demo plays lockstep matches between native and browser players through a tiny relay.

Bit-exact determinism

The same inputs produce the same frames, sounds and game state on every engine, and CI checks it with hashes. That's the basis for replays, tests and netplay.

Sandboxed by design

Games only see their own memory and the ABI. No filesystem, network only with the player's opt-in, and every pointer and handle is checked.

What's inside ​

Runnersgasm-run: native (Rust: wasmtime, wgpu, winit, cpal, gilrs), with AOT compilation for no-JIT platforms. Browser runner: WebAssembly, WebGPU, AudioWorklet, Gamepad API. Headless Node runner.
GamesSumo: 3D two-player arena with lockstep netcode. NES: a complete emulator (tetanes-core) passing the blargg CPU, timing and APU tests. DOOM: doomgeneric in C, with OPL music and saves, playing any IWAD. ScummVM: point-and-click adventures, starting with the freeware Beneath a Steel Sky. SDL 3: SDL programs build unchanged, threads included; SDL's own snake and woodeneye demos. GLES 3: OpenGL ES code through drop-in headers. Triangle and test pattern: minimal examples in Rust and C.
Toolsgasm-relay (WebSocket rooms), the gasm-sdk Rust crate (library gasm), gasm.h and the C/C++ SDK, SDL 3 for gasm, cross-runner determinism and network test suites with golden hashes.

Screenshots ​

DOOM in gasm-run
DOOM (doomgeneric in C) with OPL music, at 4:3 with the sharp filter.
Beneath a Steel Sky in ScummVM
ScummVM playing Beneath a Steel Sky, upscaled with xBR.
Sumo, the 3D demo
Sumo: gasm:gfx (WebGPU) with lockstep netplay.
GPU texture test
Mipmapped textures, samplers, instancing and dynamic offsets on gasm:gfx.
GLES 3 test in the browser player
OpenGL ES 3 C code on gasm:gl, in the browser player (WebGL 2).
SDL 3 woodeneye-008
SDL 3's woodeneye-008, source unchanged, on SDL for gasm.
The same DOOM frame with the sharp, xbr, fsr and crt filters
One 2D frame, four ways to scale it up: sharp, xBR, FSR and CRT (the player's filter menu, gasm-run --filter).

Performance ​

Measured on an Apple M1 Pro. The NES emulator compiled to wasm runs at 1.5× (wasmtime AOT) and 1.6× (V8) the time of the same Rust code built natively. That's about 9× faster than the console itself. Sumo holds 60 fps with 4× MSAA on both runners.

Status ​

gasm is a proof of concept. ABI v0 is experimental and will change. See the roadmap: gasm:gl natively, rollback netplay, .gasm packages.

MIT licensed. The NES demo core is tetanes-core (MIT/Apache-2.0).

gasm: game assembly