Architecture: process layout, module responsibilities, and data flow.
Behavior: user-visible controls, scrolling model, sensitivity, haptics, and OSD.
Input and Output Protocol: Surface Dial event decoding and virtual uinput devices.
Installation and Service: install files, udev rules, systemd user service, and logs.
Troubleshooting: raw event inspection and common failure modes.

The driver intentionally stays small. The main design choice is to keep the event loop explicit and avoid the configurable mode framework from the older daemon until there is a concrete need for it.