This is part 4, the longest of a 4-part series. The other three parts are 10-15 min each, and talk a little bit about The Legend of Zelda as a game, and show desoldering the ROM and replacing it with an EPROM. In this part, we see how to reverse-engineer how the game stores its state, how to modify the code to do things differently, and burn the result to the EPROM so it can be played on original hardware.