during drag-pacing, when you rotate the belt after you move too far to place the first belt in the new direction, you get an underground belt segment - and a reversed one for that matter!
I also found 2 other weird cases:
when you rotate the belt during drag-placing after placing just one belt, the original one does not always rotate.
- if you place 2 or more belts in the "forward" direction, then drag-placing the later single belt will rotate it
- if you then place a single belt, drag-placing another single belt will not rotate it
- if you place 2 or more belts in the "backwards" direction, then drag-placing the later single belt will make it the "end" belt of a backward moving set of belts (and that's ok)
- but if you then place a single belt, and drag place another single belt, it will be rotated too
when single belts are placed after a "forward" placing, then the remembered state is that you're moving "forward", so the last belt gets rotated when drag-placing+rotating, even if it's the only one, and that's fine.
when only one belt is placed without drag-placing, then the direction is "unknown" so with later drag-placing+rotating it doesn't know how to rotate.
when you place belts "backwards" and then place a drag-place a single one, it acts accordingly,
but for some reason placing a single belt after moving "backwards" does not reset the direction to "unknown".
when you try to wrap around and drag-build a belt over itself it will create underground belts even if it won't be fully connected (only side-connected) to the earlier belt.