Lovely article! I have a fun one to share that I noticed recently. I am 37 years old and have been doing 3D mechanical design for 15 years, including 7 years of full time CAD at the beginning. I continue to use CAD in my robot designs which I am working on almost every night. By now I am able to do a fair amount of design work in my head. I can conceptualize a new assembly with multiple parts, and focus in on specific areas to sort out how to form the shapes so that they do their job, can be assembled, and are 3D printable. It is not super high resolution but in a close-up level I can imagine any of the basic primitives you would encounter and how they mate together, and I can zoom out and imagine the part as a collection of these assemblies. It's great because I have a lot of ideas but don't want to sit at a computer all the time. I can do design work while I am on a walk or when going to sleep. And it really works!