@TheMadPirate @PurpCat @anonymous @ins0mniak

> given that MAME itself already comes with the Z80 compilation libraries.

There are a plethora of homebrew assemblers for the Gameboy. There are a couple of instructions that are different (for using XY and for dereferencing pointers in 0xff00, where the GB kept its working memory) but basically Z-80. You've got 4MB to work with, and you've got to use some register to page through the cart.