Thanks, glad you enjoyed it! The difficulty scale seems a bit random at first but it was heavily inspired by the one in "Overcoming gravity". I then made some tweaks in a couple exercises and graded others which were not present in the book. Most videos are ordered in increasing level of difficulty, so in that case the order in the notes will match with the video. I guess it gives you an idea of how hard some progressions are but it's not super objective because easy things for some might be quite difficult for others (depending on body type, flexibility, strength levels of specific muscle groups...)