How is this made??
I used the butano game engine
https://github.com/GValiente/butano
My source code is here (though be warned, it's VERY messy)
https://github.com/blaise-rascal/KnightOwls
If you want to try out gbadev, the following discord server is a great place to talk shop:
Discord
Overall, it was a lot of fun for me to make this GBA game, but I don't think I'll ever do another GBA project, simply because the GBA sound card is terrible. I really don't want to go to the effort to figure out how to use it to make good-sounding music.