The final build comprises five stacked PCBs housing the stepper motors and stepper motor drivers; each PCB has 16 stepper motors, with each one hosting an addressable RGB LED. That gives you a grid of 16 × 5 moving pixels to display the time. It’s simple, but in an admirably complex way.
Erich’s blog detailing the project build is a masterpiece of clarity; in it he outlines the build process, from single stepper motor to a wall of moving pixels. Each 3D-printed part and custom PCB is laid bare, giving us a glimpse into the work that’s gone into making this weird and wonderful timepiece.