Hi! This is an open-source game that teaches how to build an emulator from scratch. It also has a "free mode" where players can skip the tutorials and build an emulator for another platform (like the Game Boy, for example). I hope you enjoy it!
The source code is MIT-licensed and the guides are CC BY-NC. https://github.com/afska/emudevz
Show HN: EmuDevz – Open-source interactive emulator dev tutorial
afska.github.io