Sample Unity Mod Loader System

A sample Unity project demonstrating a runtime mod loader. It compiles C# source files using Roslyn (Microsoft.CodeAnalysis.CSharp) and loads them into the game.

How it works

1. Drop .cs files into Mods/YourModDirectory/.
2. Add a mod.json with metadata (name, author, entry point, etc.).
3. When game starts, the system compiles all mods into DLLs and invokes their Main() methods if they were found.
4. Mods get a basic API surface (ModAPI.Utils) to interact with the game. Implement it yourself.

Project structure

Assets/Scripts/
├── MainMenuLoader.cs         # Entry point — compiles & loads mods on Start
├── Paths.cs                  # Path resolution (Mods/, ModCompilations/)
├── ModLoader/
│   ├── ModLoader.cs          # Loads compiled DLLs
│   ├── ModCompiler.cs        # Roslyn compilation pipeline
│   ├── ModConstants.cs       # Mod metadata model
│   ├── Utils.cs              # JSON (de)serialization, validation
│   └── ModAPI/
│       └── Utils.cs          # Public API surface for mods

Example mod

// mod.json

{
  "ModName": "MyMod",
  "Author": "me",
  "Version": "1.0",
  "EntryPoint": "MyMod.ModMain"
}

// mod.cs

using ModAPI;

namespace MyMod
{
    public static class ModMain
    {
        public static void Main()
        {
            // your mod logic here
        }
    }
}

Notes

• Requires Microsoft.CodeAnalysis.CSharp NuGet package (included in Packages/)
• Mods are compiled to ModCompilations/ and loaded via Assembly.LoadFile
• Unloading mods at runtime is not supported — Mono/.NET Framework doesn't allow unloading assemblies