Changes

The schematics and PCB are 90% the same as the Spectrum's. They differ in the port decoding.

Port decoding to be confirmed.

chooses this.

Port FBEEh READ: Kempston Mouse 8 bit X position (left: -ve, right: +ve)

Port FBEFh READ: Kempston Mouse 8 bit Y position (up: +ve, down: -ve)

dist=-01h..-80h moved left/down

Port FAEFh READ: Kempston Mouse Buttons

bit 0: Right Button (active low)