A kitchen wall section. Some datums are pinned by code or ergonomics and never move. Others float relative to the ceiling. Lower the ceiling and the floaters compress until they collide with something pinned — at that point the element stops working.
Purpose: the ceiling is the one variable that cascades. Below 8'-6" upper cabinets lose height. Below 7'-6" they disappear entirely. Below 6'-6" the counter has no usable workspace above it.