We have Doxygen documentation. A lot of it! You It's built by Github Actions and hosted here. It goes over everything you could want to know about the firmware project, like how to use hardware peripherals, how to draw shapes, images, and fonts to the TFT, what random utilities already exist, and how to get a game to peacefully coexist with a bunch of other games. If you love reading documentation, give it a go! If you don't, I can't force you.