Dandanator is a programmable game cartridge equipped with a KEMPSTON joystick interface. Programs are stored in 512kB EEPROM memory, allowing lightning-fast game launch in just a few milliseconds. A single cartridge can hold 20 to 23 games.
More information about the project can be found here:
Project Dandanator
Video instructions for programming the cartridge:

Additional description of Dandanator can be found here:
Description of Dandanator
