Introducing, a prototype of what I am tentatively calling the Arduboy 'Classic'. Using an Arduino Leonardo (same ATmega32U4 microcontroller as the Arduboy), but with the screen, the buttons, the speaker, and the LED indicator all being provided by the front half of a classic Nintendo GameBoy!
Full details on the Arduboy forum: http://community.arduboy.com/t/arduboy-classic/293
