GB#

A statically compiled, hardware-aware C# development environment for the Game Boy and Game Boy Color.

GB# is not ".NET for Game Boy". There is no CLR, no JIT, and no garbage collector on the target. You write a constrained subset of C#; GB# analyses it with Roslyn, lowers it to a small intermediate representation, emits conservative C, and hands that to GBDK-2020 to produce a .gb or .gbc ROM.

C# → Roslyn → GB# validation → GB# IR → C → GBDK-2020 / SDCC → ROM

The bet is that modern language ergonomics do not require a modern runtime.

using GB;
using static GB.Hardware;

public static class Program
{
    public static void Main()
    {
        Display.Enable();

        byte x = 80;

        while (true)
        {
            if (Input.Right)
                x++;

            Sprites[0].X = x;

            Game.WaitVBlank();
        }
    }
}

That compiles to C where the whole Sprites[0].X chain erases to a single OAM store and the arithmetic stays 8-bit. GB# abstracts boilerplate, not hardware.

Start here

• Installation: the .NET SDK, dotnet tool install --global gbsharp, and gbsharp doctor --fix for everything else.
• Your first game: gbsharp new to a running ROM in minutes.
• Tutorials: worked walkthroughs of the sample games, from one moving sprite to a banked 64 KB cartridge.

Find your way

• Guides: the C# subset, assets, banking, memory, diagnostics, profiling, publishing.
• CLI reference: every gbsharp command and option.
• gbsharp.json reference: every project file key.
• Diagnostics reference: all GBSxxxx ids, generated from the compiler's own definitions.
• Framework API: the GB namespace your game code compiles against, generated from the source XML docs.

For language models

This site publishes an llms.txt index and an llms-full.txt containing the complete manual in one file, for use by LLM-based tools working with GB#.

Design and internals

The user documentation lives here. The design rationale (why a compiled subset instead of a runtime, why the IR looks the way it does, and what GB# refuses to become) lives in GBSharp_Thesis_and_Architecture.md in the repository, alongside the roadmap.