I always found mappers and additional hardware in cartridges fascinating. NES does not support saves? Just put a battery and additional memory in cartridge to s

I always found mappers and additional hardware in cartridges fascinating. NES does not support saves? Just put a battery and additional memory in cartridge to store your data. No animations? Add more pattern tables and cycle through them during the game. An interesting way to keep your console's price low and add some extensibility at the cost of making cartridges more expensive.