The demos[0] and the inspectability of them are both really amazing! I'm reminded of Deprecating the Observer Pattern[1], which looks at an FRP approach to drag-n-drop - it's a good read and shows that we've never had a solid idiomatic approach to such an elemental interaction.

I have a growing hunch that state machines, possibly extended for greater composition as in statecharts[2], are the best way to represent many UIs. They're declarative and represent change as a first-class thing: an `arrow`. Functions and methods don't map well to this concept and I think that's why it's a bitch to specify state machines in code. Maybe we gave up too early with `goto`

[0] https://declarative-dragging.github.io/dragology/#/demos

[1] https://news.ycombinator.com/item?id=17845341

[2] https://news.ycombinator.com/item?id=25454175