zigboy

Game Boy emulator built from scratch in Zig. CPU, PPU, memory, and cartridge subsystems.

Build

zig build run

Requires Zig 0.13+.

Features

• CPU emulation (Sharp LR35902 instruction set)
• Memory management (VRAM, WRAM, HRAM, I/O registers)
• Cartridge loading (ROM banks)
• PPU (pixel processing, scanlines)
• Sound (audio channels)
• Input (joypad)
• WebAssembly compilation target

Architecture

┌─────────────────────────────────────┐
│  CPU (Sharp LR35902)                │
│  • 8-bit registers (A,F,B,C,D,E,H,L)│
│  • 16-bit SP, PC                    │
│  • 512 opcodes + CB prefix          │
└──────────────┬──────────────────────┘
               │
┌──────────────▼──────────────────────┐
│  Memory (64KB address space)        │
│  • 0x0000-0x7FFF: ROM (cartridge)   │
│  • 0x8000-0x9FFF: VRAM (tiles)      │
│  • 0xC000-0xDFFF: WRAM              │
│  • 0xFF80-0xFFFE: HRAM              │
└──────────────┬──────────────────────┘
               │
┌──────────────▼──────────────────────┐
│  PPU (Picture Processing Unit)      │
│  • 160x144 LCD                      │
│  • Tile-based rendering             │
│  • 4 shades of gray                 │
└─────────────────────────────────────┘

References

• Pan Docs — The Game Boy technical reference
• GBEDG — Opcode behavior
• Blargg's test ROMs — CPU validation

Usage

Load a Game Boy ROM and run:

zig build run -- path/to/rom.gb

Compiles to WebAssembly for browser deployment.

License

MIT