Epsilons and Deltas

What did you use to anonymize the photos with the stylization? I really like how those photos are stylized. And there's some neat ideas here.

There's a book called Exploring Curvature by James Casey that has a lot of little physical experiments and constructions for exploring differential geometry. You may be interested in it.

And Tadashi Tokieda has a lot of lectures on YouTube along these lines as well, where he'll have students cut out strips of paper to explore topological ideas.