Webleste

A mostly-complete port of Celeste (2018) to WebAssembly, with full support for Everest mods. Powered by FNA-WASM-Build and MonoMod.WASM.

^{Strawberry Jam running in Webleste}

Limitations

• Loading the game consumes 600M or so of memory, which is still around 3x lower than the original port, but it is still too much for low end devices.
• You may encounter issues on Firefox.

I want to build this

1. Ensure node and pnpm exist and pnpm i
2. Install dotnet 9.0.4
3. Install the mono-devel package on your distro
4. Run sudo dotnet workload restore in loader/
5. Run make serve for a dev server and make publish for a release build

I want to figure out how this works

• The native dotnet WASM support is used to compile a loader program to WASM
  • loader/Celeste.cs loads a patched Celeste assembly and exports a function that polls its main loop
  • loader/Patcher.cs runs MonoMod on celeste assemblies provided by the user to patch it for WASM
  • patcher/ has the source for the MonoMod.Patcher mod used for WASM patches
• A WASM port of MonoMod is used to provide detours/hooks to Everest and other runtime mods, it functions completely on the IL level and is mono specific
• FMOD pthread builds are used for audio, with slight patching of the bindings so that using FMOD 2 works
• The game canvas is transferred to dotnet's "deputy thread" and all rendering is done from there through FNA's OpenGL driver

For a deeper dive into how we made this and the Terraria web port, check out the writeup.

I want to port this to a newer version of Celeste (once it exists)

1. Fix any issues with the hooks
2. Make a PR!