Developer Nick Kossolapov created a full-fledged Game Boy emulator in F# in an effort to gain a deeper understanding of computers. The Fame Boy project, which grew out of educational experiments with CHIP-8 and the From NAND to Tetris course, supports graphics and sound and works on both desktop and browser. The author described in detail the architecture of the emulator, the trade-offs between functional style and performance, as well as the role of AI — from generating tests to finding critical bugs.