I do not have a cool video to share - only dry text! 🙂 but I think there is a very interesting "interaction pattern" that comes up in a lot of simple programming systems (at least the ones that I sometimes work on) - so this is an attempt to capture that... Choose-your-own-adventure calculus: https://tomasp.net/blog/2025/adventure-calculus/

"The basic motivation for a lot of my recent work has been the fact that programming systems are much more interesting and important than programming languages. A language is always embedded in some system, but the properties of the system matter more than the properties of the language. And while we know very well how to study programming languages, we only know little about how to study programming systems."

I really like this point.

This is neat! I really like how you are able to unify interaction paradigms from domains that are usually considered very far from each other (namely, data analysis and interactive theorem proving). I hope a lot more people in the PLT community will gradually shift their focus from languages to systems.

Thanks @Pablo Donato - and yes, we totally need to convince people that systems ⊃ languages!