ZGB is a Game Boy / Game Boy Color engine that lets you write your own games in C or asm.
It uses GBDK 2020 but expands it to give you some common functionallity for writing games such as: a main loop, sprites spawning, sprites life cycle, sprites animations, collison management, easily getting assets into the game, music, fx...
https://github.com/Zal0/gbdk-2020
https://gbdev.gg8.se/wiki/articles/ZGB_Installation_Tutorial