Cool! cool DS15 used to be a speedcuber too. His 3x3x3 PB was sub10 when he was 13. One handed 3x3x3 was his favourite competition event (PB is sub18). Finger dexterity from years of speedcubing now serve him well for playing musical instruments. The other types of puzzles (pyraminx, gear cube, mirror cube) likely also helped to develop 3D geometry problem solving abilities.

I recall a cute anecdote related to speedcubing - in upper primary, DS’s three best friends also became interested in speedcubing so when they started high school together, they all carried their 3x3x3 cubes around everywhere. His now best friend came from a different primary school and really wanted to join this group of friends - he apparently announced he was going to save his pocket money to buy a Rubik’s cube so that he could be one of their group. At the time I hadn’t met this child, but what he said seemed so cute, I bought a speed cube and asked DS to give it to him.