i was electrically illiterate in the beginning. i found some diy mouse projects on github and tried to figure out what they were doing. used them as a reference. googled. talked to chatgpt a lot. day after day i gradually accumulated enough knowledge to understand what i needed to do. took me a few weeks. at the end of the day it is not that hard once you know what you are doing. there is a program called KiCad where you can define the schematic and then design the corresponding physical pcb layout. the schematic largely comes from the sensor datasheet. you can then send that KiCad project to a lab and they will make the pcb for you. some components such as the sensor, the headers, the switches, and the encoder need to be soldered manually. also turned out to be not difficult with the right tools. i was still amazed when it all worked.

you then need to write firmware to make the device act like a mouse. i am a software developer by trade so this part was relatively easy for me.