Advanced Mac Substitute reimplements 1980s Mac OS at API level

Advanced Mac Substitute provides a complete reimplementation of 1980s-era Mac OS at the API level, enabling 68K Mac applications to run in an emulator without requiring original Apple ROM or system software. Unlike traditional emulators that replicate hardware, this project replaces the operating system entirely, allowing direct application launch without startup phases. The system successfully runs several classic Mac applications including games from 1984 like Amazing, Solitaire, Missile, and IAGO, as well as productivity software like MacPaint and Lode Runner. Current features include support for 1-bit graphics, regions, shapes, text rendering, windows, controls, menus, and dialogs. The project uses a factored architecture with a 68K emulator backend that builds on POSIX systems, and frontend implementations for SDL2, macOS, X11, and Linux framebuffer. Source code is available on GitHub for developers interested in exploring or contributing to the project.