The Wii was a massive commercial success because it managed to make video games seem approachable to everyone — even your grandmother. A major part of that approachability was a result of the incredibly innovative motion controls. Games were played with either the standard Wii Nunchuk controller, which could be connected with a cable to the Joystick controller in your other hand, or the classic controller. Both the Nunchuk and Joystick controllers had accelerometers for motion control. Thingiverse Keycaps wanted to take advantage of the Joystick’s motion capabilities for a unique application, and so they stuffed a Raspberry Pi Zero W inside one.
Keycaps built this control an organization program that they made, but points out that it could be used as a custom controller for video games as well. The Wii Joystick controller had two buttons, a joystick, and an accelerometer, which makes it pretty versatile. You could, for example, use it as a mouse for your computer. In this case, Keycaps needed a Raspberry Pi to make it work with their program. The challenge was fitting all of the required hardware inside of the controller.
That hardware includes the original controller’s PCB and buttons, as well as a Raspberry Pi Zero W, a LiPo battery, and Adafruit Powerboost LiPo battery management board, and a mini HDMI to HDMI adapter board. That was far too much to fit inside the original controller enclosure. So, Keycaps just kept the top cover and 3D-printed the bottom half of the enclosure to contain the hardware. There is already existing software that lets the Raspberry Pi recognize the signals from the Wii Joystick controller, so Keycaps just had to install that in order to start using the controller with their program.