Slay the spire 2 mod example

Example mod project made according to STS2 Early Access Mod Guide by doctornoodlearms on r/slaythespire. Ported to game v0.99+.

My process for building this mod on macOS Apple Silicon:

1. Install Godot 4.5.1 .NET version, e.g., Godot_v4.5.1-stable_mono_macos.universal.zip for macOS, Godot_v4.5.1-stable_mono_linux_x86_64.zip for Linux

2. Install .NET SDK, e.g., dotnet-sdk-10.0.200-osx-arm64.pkg for macOS, use nixpkgs for Linux

3. Open Godot, create a project, name it FirstMod

4. In the Script tab, click File -> New Script..., select .NET as the language, name it NewScript.cs, and fill in the following content:

   using Godot;
   using MegaCrit.Sts2.Core.Modding;
   using MegaCrit.Sts2.Core.Logging;
   
   namespace FirstMod;
   
   [ModInitializer("ModLoaded")]
   public static class FirstMod {
       public static void ModLoaded() {
           Log.Warn("MOD FINISHED LOADING");
       }
   }

5. Copy the game's sts2.dll (e.g., ~/Library/Application\ Support/steam/steamapps/common/Slay\ the\ Spire\ 2/SlayTheSpire2.app/Contents/Resources/data_sts2_macos_arm64/sts2.dll on macOS, ~/.steam/steam/steamapps/common/Slay\ the\ Spire\ 2/data_sts2_linuxbsd_x86_64/sts2.dll on Linux) to the project root directory

6. Modify FirstMod.csproj as shown below, change the .NET version to 9.0, add a reference to sts2.dll, then click Build Project in Godot:

   <Project Sdk="Godot.NET.Sdk/4.5.1">
   <PropertyGroup>
       <TargetFramework>net9.0</TargetFramework>
       <EnableDynamicLoading>true</EnableDynamicLoading>
   </PropertyGroup>
   <ItemGroup>
       <Reference Include="sts2">
           <HintPath>sts2.dll</HintPath>
       </Reference>
   </ItemGroup>
   </Project>

7. Create FirstMod.json in the project root directory:

   {
       "id": "FirstMod",
       "name": "FirstMod",
       "author": "doctornoodlearms",
       "description": "",
       "version": "1.0.0",
       "has_pck": true,
       "has_dll": true,
       "dependencies": [],
       "affects_gameplay": true
   }

8. Prepare an image named mod_image.png in the FirstMod directory under project root directory for the mod's icon

9. Go to Project -> Export..., click Add..., and select Windows Desktop

10. Under the Resources section, select Export selected resources (and dependencies), tick FirstMod/mod_image.png, then click Export PCK/ZIP..., save as FirstMod.pck. You can also export via command line, e.g., /Applications/Godot_mono.app/Contents/MacOS/Godot --export-pack "Windows Desktop" FirstMod.pck --headless

11. Copy FirstMod.json, ./.godot/mono/temp/bin/Debug/FirstMod.dll and FirstMod.pck to the FirstMod directory under the game's mods directory, e.g., ~/Library/Application\ Support/Steam/steamapps/common/Slay\ the\ Spire\ 2/SlayTheSpire2.app/Contents/MacOS/mods/FirstMod (macOS) or ~/.steam/steam/steamapps/common/Slay\ the\ Spire\ 2/mods/FirstMod (Linux), create the directory if it doesn't exist

12. Launch the game

A build script is provided at build.sh to build the mod without GUI. An installation script is provided at install.sh to install the mod automatically. Tested to build & run in both macOS and Linux.

What's next:

1. Decompile the game:

   git clone https://github.com/icsharpcode/ILSpy.git
   nix-shell -p dotnet-sdk_10 -p dotnet-runtime_10 -p powershell --run "cd ILSpy && dotnet build ILSpy.XPlat.slnf && dotnet ./ICSharpCode.ILSpyCmd/bin/Debug/net10.0/ilspycmd.dll -o $PWD ~/.steam/steam/steamapps/common/Slay\ the\ Spire\ 2/data_sts2_linuxbsd_x86_64/sts2.dll --nested-directories -p"

2. Read the code, and make modifications in runtime by reflection or Harmony.

3. For runtime debugging, you can use plain logging or start Godot's Debug Server:

   1. In Godot, select Debug -> Keep Debug Server Open
   2. In Steam, set the launch option --remote-debug tcp://127.0.0.1:6007
   3. Launch the game