The Neptune 4 has an ancillary Screen controller not part of the printer itself that attaches via a serial tty connection and communicates with the printer host. It is a separate microcontroller from the printer entirely, has its own processor and its own firmware which must be updated in tandem with Elegoo's printer 'firmware' updates. It support Elegoo designed workflows for controlling the printer distinct from the Fluid GUI that Klipper supports for workflows and controls.