I'm trying to re-find a nested folding docs site. It was styled to look like Google Docs.

I read an article there, a detailed report, possibly from Redwood Research, covering an argument and deep, iterative explanation that could be read as a single paragraph of headers, each unfolding into a paragraph of sub-headers, readable as coherent paragraph or outline, each of which again, had anything from 2 lines to a few paragraphs of argument, description, and diagrams. 

I haven't found it in my browser bookmarks, full-text archives, HN search, nor searching familiar looking LessWrong and AlignmentForum links.

The site, and the particular document's structure and content, offered presentation of information made enough of an impression that I've described it to a few people. I'd like to find the site again, use it, and share it with some other people who want to make some documents with deep detailed explanations, accessible through incrementally unfolded explanations.