For the Atari 2600, Game Boy, etc., the first cartridges were nothing more than a ROM chip on a printed circuit board. Later games sometimes included a lot mor

For the Atari 2600, Game Boy, etc., the first cartridges were nothing more than a ROM chip on a printed circuit board. Later games sometimes included a lot more functionality on the cartridge (battery-backed save RAM, bank switching hardware, etc.) which does make things complicated very quickly. Today, programmable logic is sometimes used to replace old custom IC designs used in cartridges, or to design something new. For games more complicated than a simple ROM chip, the Game Boy presents an interesting challenge: the cartridge is both very small and it needs to be able to run off battery power. That excludes using both a high-power-consumption modern SoC or FPGA, or using lots of discrete logic. But if it'll fit in 32 KB, it's 3D print a case, order a PCB, and program a standard Flash chip.