Using very little hot glue, mount two buttons onto the ring. They can technically be placed anywhere, but the positions in the picture above is recommended since they're easy to reach and far away enough from the touch sensor to not accidentally activate it. However, choose whatever position works for you.

Speaking of the touch sensors, remember the touch wire? Its purpose is to extend the activation area of the board, and now is a good time to wrap it around the trackball as shown in the picture (wrapped around the top right and bottom left holes). Wrap them in a way that's simultaneously easy for you to reach and activate and not likely to be accidentally triggered.

Reference the diagram below about the workings of a push button:For the upper button (the button parallel to the Xiao) wire A --> GND and D --> D3

For the lower button (the button perpendicular to the Xiao) wire A --> GND and D --> D2

Sometimes, the buttons can be hard to press, so it's recommended to add a little piece of plastic on top of it to make it easier to press like the image above.

Once these buttons are wired, test everything's connectivity. After that, glue the trackball down.

Download the code from the Github repo here: https://github.com/sophia-08/WeAreTheRats.

Once downloaded, open the WeAreTheRats.ino file in Arduino and from Board Manager, install "Seeed nRF52 Boards" (NOT "Seeed nRF52 mbed-enabled Boards") . Connect the Xiao board on the ring via USB-C to your computer, select the corresponding board in Arduino, hit compile, and flash the code onto the board. 

All the processing should happen on the XIAO, so turn on the ring and connect it via Bluetooth to whichever device (it should appear on the computer as Rat0). Check out the YouTube video I made here to see all of what ErgO can do.

Test all of its capabilities as shown in the diagram: 

:)