The idea early on was to leverage existing Arduino libraries to connect with a standard USB mouse, specifically, the hardware would take the form of an Arduino Mega 2560 with a USB Host Shield ...

That means you can have the CUI appear to be any USB HID device you want: keyboard, mouse, game controller, etc. The Arduino has a friendly development environment and a large following though.

We've shown you one way to do this before, but this method gives you better access to the USB. To do this for yourself, you'll need a full size USB mouse, a small USB hub, Sugru, and a USB pinout.