The Nintendo Entertainment System, or NES, defined the look and feel of "video games" for an entire generation. At its core, it featured a MOS Technologies 6502 processor and a custom "Picture Processing Unit". All of your favorite games for the system were written in assembly, and with modern tools, you can write your own games for the NES in assembly too! We'll start with a look at how binary numbers work, and then jump right in to 6502 assembly and how the NES works at the hardware level. Finally, we'll look at some common tricks used by popular games and how to get started working on your own games.