Glad you enjoyed. I think mediums like Scrimba's are very interesting. I've discussed them as "narrated explorables" here: https://medium.com/khan-academy-early-product-development/narrated-explorables-three-mental-models-e16e0d80e4c1 … I think the key thing about exec. books is "shipping the author's computational model," which isn't quite what's happening here.
Those were laborious one-offs, as I understand it. @ben_eater?