Nyxx – NES Emulator in Zig

A minimal 6502 CPU emulator written in Zig.

Overview

Nyxx is designed with clarity and modularity in mind. It targets the Ricoh 2A03 — a custom variant of the MOS 6502 used in the Nintendo Entertainment System (NES). This makes Nyxx suitable for building NES emulators, tools, or educational systems that simulate 8-bit era behavior.

Pronunciation

Nyxx is pronounced Nix (/nɪks/), as in Nyx, the Greek goddess of the night. The name draws inspiration from Nyx and follows the tradition of Unix-like systems by appending an "x" to the end, forming Nyxx as a minimal, modern homage to classic systems.

Requirements

This project only depends on Zig and can be built on any modern system.

• Zig version 0.14.0
• LLVM version 19.1.3

Nyxx supports multiple frontend implementations. You can choose between:

• WebGL (via WASM export) For in-browser rendering
• SDL2 (tested with libsdl2 version 2.32.2) For native desktop display

The frontend can be selected at build time. The core emulator (CPU/PPU/etc.) remains platform-independent.

Build & Run

Nyxx is built with Zig. You can compile and run it for both native desktop or browser environments.

Native (SDL2 frontend)

To run with native SDL2 frontend:

zig build
./zig-out/bin/nyxx $PATH_TO_ROM_FILE

WASM (WebGL frontend)

To compile for the web frontend:

zig build wasm

This produces a nyxx.wasm binary, which requires a JavaScript engine to run (e.g. 6502.city).

Documentation

Explore detailed docs and implementation notes on Notion: Project Nyxx

Design Priorities

• Keep the codebase minimal, readable, and portable
• Avoid unnecessary abstraction; show the structure
• Export as a WASM runtime for live interaction
• Emulate the 6502 CPU with instruction-level accuracy

License

This project is licensed under the MIT License. Copyright (c) 2025 Kei Sawamura a.k.a. keix