A simple endless runner game built for Arduino.
I utilized Joseph's very useful tutorial for understanding the NES controller's logic and circuitry. You can find the article here: https://www.allaboutcircuits.com/projects/nes-controller-interface-with-an-arduino-uno/.
I then used his layout for the socket of the NES controller's plug to trace back which terminals led to where on the PCB. I took out the 20+ year old wires and soldered in some new ones that could be directly and more securely connected to my Arduino Uno.
Here it is in action: https://giphy.com/gifs/Vgg4n1c5OweMIa5SWb