This repository is a Godot 4 addon that integrates the libsm64 library (a reimplementation of Super Mario 64's game engine) into Godot via GDExtension. It provides both a low-level C++ API exposed as a Godot singleton (`LibSM64`) and high-level GDScript nodes (`LibSM64Mario`, `LibSM64StaticSurfaceHandler`, `LibSM64SurfaceObjectsHandler`, `LibSM64AudioStreamPlayer`) for easily adding Mario characters and surface geometry to Godot scenes. The addon handles coordinate system conversion (SM64 to Godot), fixed-rate physics ticking at 30 FPS with interpolation for smooth rendering, and dynamic material switching based on Mario's power-up state. A demo project with multiple playable scenarios (Bob-omb Battlefield, many Marios, flying range) is included, along with a ROM picker dialog for loading the required Super Mario 64 US ROM. The architecture is a classic Godot plugin: a GDExtension shared library (built from C++ source in `extension/`) registers new engine classes and a singleton, while GDScript files in `addons/libsm64_godot/` provide editor integration and higher-level abstractions. The core C++ code wraps all libsm64 functions (global init, Mario creation/tick, surface loading, audio) and exposes them as Godot methods. The GDScript layer adds node lifecycle management, input mapping, interpolation, and surface handling utilities. The demo project in `libsm64_godot_demo/` showcases the addon with custom scenes, a camera rig, HUD, and input configuration. Key external dependencies are the libsm64 C library (included as a Git submodule) and the godot-cpp bindings (also a submodule). The addon requires a specific Super Mario 64 US ROM (SHA-256 verified) to function, as libsm64 uses original game assets. The build system uses SCons and GitHub Actions to compile the GDExtension for Windows, macOS, Linux, and Web platforms. The code is well-structured with clear separation between C++ engine bindings and GDScript gameplay logic, making it a solid reference for integrating complex C libraries into Godot.