The author built a CHIP-8 emulator in Rust called Fortress to run 50-year-old games, choosing the project to learn systems programming concepts like memory layout, bitwise operations, and the fetch-decode-execute cycle. After discovering a year-old Zig emulator and deciding to rewrite it in Rust, they debugged complex issues and successfully launched classic games like Pong, describing the experience as building a time machine between retro software and modern hardware.