It's really nice seeing people get some use out of something I made as a little personal "how do they do that" - the video that got me thinking about it is the same one at the start of the Tumblr post, as someone who likes impressive books and also dabbles in bookbinding, it was a no-brainer to give it a shot. As a one-time maths teacher, it was a fun bit of geometry to figure out. Thank you for the comment!