First of all CHIP-8 is an interpreted language developed long time (1970s) ago by Jospeh Weisbecker. It was used to program 8-bit computers like COSMAC VIP and Telmac 1800. Anyway there doesn’t seem much use of it, but in other hand back then using this language a number great games (Pong, Space Invaders, Tetris and Pac-Man) were created. So in order to run them you need to emulate CHIP-8. So Mat put a simple game emulator around PIC24 microcontroller.
He used a cheap Nokia1202 LCD, 16 + 4 buttons, battery and UCB which turned out to be buggy due to messed up PCB. But this doesn’t stop from running programs. Such keypad arrangement was used because machine back then had this hexadecimal arrangement. There are few issues left, the onewith USB, second with display. Because CHIP-8 requires 64×32 resolution, while screen has 96×68. So some sort of image stretching is required. And there is no sound beeper. Anyway, this is great retro experience.