At risk of pulling in too much fanciness, I've seen @jrus use viewof in some interesting ways, e.g. https://observablehq.com/@jrus/widthview which definitely had some viewof tricks I'm not familiar with! Maybe worth a link.

Interesting, but not necessarily a good example for viewof, because you can do the same without viewof, by wrapping the value inside an object. Besides, this notebook is really meant to be as short and non-technical as possible. There may already be dozens of notebooks covering viewof, and I was at first hesitant to add one more to the pile. But I think this notebook may do a better job than some at priming the reader, and at getting straight to the point.