Have you ever wondered why there are only 7 pins on the NES controller port, but 8 buttons (plus power and ground)? How does the NES know exactly what button is being pushed? Also, how long does it take for the console to know that you’re pushing a button at all?
Well, lucky for us, Displaced Gamers has a video that explains exactly what’s going on. They start out with the basics of how a controller is laid out, but quickly get to the good stuff! Also, they describe what a “shift register” is in a way that’s really easy to visualize and understand.
While it might get a little in-depth for beginners, I still highly recommend the video; Even if you don’t fully understand the ending, it’ll plant the seed for a better grasp of how almost all classic controllers work!