11:03 PM, Sunday December 27th 2020
Ok so for the mirror plane it can be at any angle, but the tilted plane has to be at a different angle relative to the mirror plane. It doesn't matter what orientation the mirror plane is as long as it has no 3rd VP and it isn't rotated. The mirror plane does have to be next to the tilted plane so it can mirror properly. You have to able to do the red lines on page 36 in order for the mirror plane to work. This is my two cents on it, but I literally just did that page like a couple days ago. Sorry for the sucky grammar.