So the drawing code redraws the entire UI from scratch at each loop. This seems to work OK for now, when the UI consists of printing out a couple of lines to the console.

But what if we wanted a more ncurses type UI, with persistent indicators of the score, current location, etc, and some chrome around them? The impetus to do some kind of change-based incremental updating of the display would get strong, I would think. How is this generally handled in functional-reactive type UIs?