A self-contained C# game in 8 kB

This repo is a complement to my article on building an 8 kB self-contained game in C#. By self-contained I mean this 8 kB C# game binary doesn't need a .NET runtime to work. See the article on how that's done.

The project files and scripts in this repo build the same game (Snake clone) in several different configurations, each with a different size of the output.

😱 Scroll all the way down for instructions on how to run this on DOS.

Building

To build the 65 MB version of the game

dotnet publish -r win-x64 -c Release

To build the 25 MB version of the game

dotnet publish -r win-x64 -c Release /p:PublishTrimmed=true

⚠️ WARNING: additional requirements needed for the below configuration

Make sure you have Visual Studio 2019 installed (Community edition is free) and include C/C++ development tools with Windows SDK (we need a tiny fraction of that - the platform linker and Win32 import libraries).

To build the 4.7 MB version of the game

dotnet publish -r win-x64 -c Release /p:Mode=CoreRT

To build the 4.3 MB version of the game

dotnet publish -r win-x64 -c Release /p:Mode=CoreRT-Moderate

To build the 3.0 MB version of the game

dotnet publish -r win-x64 -c Release /p:Mode=CoreRT-High

To build the 1.2 MB version of the game

dotnet publish -r win-x64 -c Release /p:Mode=CoreRT-ReflectionFree

To build the 10 kB version of the game

dotnet publish -r win-x64 -c Release /p:Mode=CoreRT-NoRuntime

To build the 8 kB version of the game

1. Open "x64 Native Tools Command Prompt for VS 2019" (it's in your Start menu)
2. CD into the repo root directory

csc.exe /debug /O /noconfig /nostdlib /runtimemetadataversion:v4.0.30319 MiniRuntime.cs MiniBCL.cs Game\FrameBuffer.cs Game\Random.cs Game\Game.cs Game\Snake.cs Pal\Thread.Windows.cs Pal\Environment.Windows.cs Pal\Console.Windows.cs Pal\Console.cs /out:zerosnake.ilexe /langversion:latest /unsafe

Find ilc.exe (the CoreRT ahead of time compiler) on your machine. If you completed any of the above steps that produce outputs <= 4.7 MB, ilc.exe will be in your NuGet package cache (somewhere like %USERPROFILE%\.nuget\packages\runtime.win-x64.microsoft.dotnet.ilcompiler\1.0.0-alpha-27402–01\tools).

[PATH_TO_ILC_EXE]\ilc.exe zerosnake.ilexe -o zerosnake.obj --systemmodule:zerosnake --Os -g

link.exe /debug:full /subsystem:console zerosnake.obj /entry:__managed__Main kernel32.lib ucrt.lib /merge:.modules=.rdata /merge:.pdata=.rdata /incremental:no /DYNAMICBASE:NO /filealign:16 /align:16

Contributing

Contributions are welcome, but I would like to keep the game simple and small. If you would like to add features like levels or achievements, you might want to just fork this repo.

In general, I welcome:

• Making the 8 kB version of the game run on Linux and macOS (the bigger versions of the game should work just fine on Unixes, but the tiny version that p/invokes into the platform APIs is OS specific)
• Adding a configuration that builds the game as an EFI boot application so that it can run without an OS
• Bug fixes
• Making the CSPROJ also handle the 8 kB case so that we don't need to mess with the command prompt
• Small experience improvements (e.g. handling ESC key to exit the game)

To build for DOS

Very similar instructions to the 8 kB version:

csc.exe /debug /O /noconfig /nostdlib /runtimemetadataversion:v4.0.30319 MiniRuntime.cs MiniRuntime.Dos.cs  MiniBCL.cs Game\FrameBuffer.cs Game\Random.cs Game\Game.cs Game\Snake.cs Pal\Thread.Dos.cs Pal\Environment.Dos.cs Pal\Console.Dos.cs Pal\Console.cs /out:zerosnake.ilexe /langversion:latest /unsafe

[PATH_TO_ILC_EXE]\ilc.exe zerosnake.ilexe --systemmodule:zerosnake -o zerosnake.obj

link /subsystem:native /entry:__managed__Main zerosnake.obj /stub:dos64stb.bin

The DOS64STB blob is https://github.com/Baron-von-Riedesel/Dos64-stub.

Run on UEFI

To build the 11 kB Uefi version of the game

dotnet publish -r win-x64 -c Release /p:Mode=CoreRT-Uefi

This produce UEFI executable stored on the VHDX file in the bin\x64\Release\netcoreapp3.1\win-x64\native\seesharpsnake.vhdx location, now it's time to create VM out of that VHDX file and launch it.

Open Powershell or Powershell Core session and run commands below.

New-VM -Name SeeSharpSnake -MemoryStartupBytes 32MB -Generation 2 -VHDPath "bin\x64\Release\netcoreapp3.1\win-x64\native\seesharpsnake.vhdx"
Set-VMFirmware -VMName SeeSharpSnake -EnableSecureBoot Off
Set-VM -Name SeeSharpSnake -AutomaticCheckpointsEnabled $false -CheckpointType Disabled

and now connect to your VM using

vmconnect localhost SeeSharpSnake

Press Ctrl+S and enjoy!