went to grandparents' mini pre-thanksgiving lunch, got to see all the (young) local cousins.
grandparents had given 6th grade cousin a book of riddles, one of them was something about a ring that was square. that put me in mind of mathematical rings (as in group, ring, field) so I showed him a permutation group based on rotating, flipping, etc a square with labeled corners & he was super interested so we were the last to the lunch table.
afterwards he came over and "can you give me some math please?" so gave him a very shotgun crash course on complex numbers as vectors, what vectors are, and how multiplying complex numbers rotates them. he drank it all up.