Waffle said: why not just hack a rom?
Er, a rom is just read-only-memory. I’m assuming you’re referring to those VBA ROMs? XD
By hacking a rom, that’s only changing some values in a game made by someone else/company, you aren’t “making a new one.” This is an original game. You can’t just hack up a game, and change stuff, doesn’t work that way.
There have been people making custom games in the past, then making them into roms, which a emulator can then read, but this is a different style – it’s not the same concept as the stuff you see with VBA, which emulates the game boy.