Just had to rewrite a bunch of the placement logic for Octavo, my PDF imposition/printing Mac app. It was a bit of a rabbit hole, there were a bunch of bugs and bad assumptions interacting together, and as soon as I wanted to place a page slot rotated 90 degrees, they all came to the surface.
Fixed and unit tested now.
As a reminder, the TestFlight beta is open: https://octavo.pro
