Although Bret Victor's ideas behind reactive documents are interesting, I think the first example on this page (regarding the state parks) is particularly unfriendly and difficult to gain any understanding from. My views very closely aligns with (and was influenced by) Evan Miller's blog post [1] on the top that I highly recommend you read. The overall gist is that equations are actually the friendliest way to spread information about the relationships between several (ie more than 3 or 4) variables.
The final paragraphs of Evan Miller's essay address this particular webpage (the Tangle demo) in particular.