Please note this is a working emulator, and is still being actively worked on
Pokemon Red/Blue/Yellow/Silver/Gold
Tetris
Mario Land
Here are some good sources if you are looking for help in developing one:
https://izik1.github.io/gbops/index.html
https://github.com/Baekalfen/PyBoy/
https://gekkio.fi/files/gb-docs/gbctr.pdf
if you read through my code and spot any mistakes, let me know :)
Thanks!