It's a nice article and the animations are functional and aesthetically pleasing. I used to teach this on a whiteboard at my local community college. This is much slicker (and involves a lot less scribbling and erasing).

Spanning tree is an elegant protocol for the constraints it was invented under. Radia Perlman's poem-- particularly the last two stanzas-- also makes me very happy.

Aside: I enjoy the typographical error in the paragraph under the "Topology change notification" heading:

When a link fails, a connected fridge reachable...