eggvance is a fast and accurate Game Boy Advance emulator written in C++. The processor grew instruction by instruction in conjunction with its test suite to ensure a solid implementation with all edge cases covered.
Other components of the system soon followed, and the emulator got to a stage where it was able to run most games and demos you threw at it. Around that time, I spent a weekend porting it to WebAssembly. Audio emulation was something I had been putting off until the end due to my lack of experience, but I managed to do it eventually.
The final year of development went into performance and accuracy improvements. I released version 1.0 around 2.5 years after the initial commit and wrote a couple of progress reports along the way. If you're interested in that kind of stuff, you can check them out here.