@SapphicLawyer No idea, never had a Game Gear and don't know much about it. Since I am already at the limit of the rp2040 the slightly better specs of the GG might require a faster micro processor (or FPGA). Whether the principle works here also depends on how much the Game Gear reveals on the memory bus. For example, it is very useful that the Game Boy sets the address pins of the cartridge to the current program counter even when it is executing code from RAM.