Yeah, that was my first thought. The author thinks they are extending CSS, but actually reinvented HAML with CSS syntax. CSS as a language is supposed to apply

Yeah, that was my first thought. The author thinks they are extending CSS, but actually reinvented HAML with CSS syntax. CSS as a language is supposed to apply to an existing DOM tree, not synthesize an entirely new one. The selector syntax alone is too ambiguous to actually do that, because it is a search lookup, not a tree structure (even though SASS/LESS can make it look like one). If you specify, say, three `svg path` selectors with rules in them, you aren't asking for three separate paths in an SVG node. You're asking for all paths in all SVG elements, including grandchildren and great-grandchildren, to be handed all of the rules in all matching selectors. If we wanted to make this idea work while not redefining CSS selectors, we'd have to ban the descendent combinator (because it would create infinite node hierarchies), and use the child combinator and nth-child everywhere exclusively. So instead of `svg path` you'd have `svg > path:nth-child(1)`. And probably a `::synthesize()` selector for saying, "yes I want this CSS rule to create a DOM node".