Why "We use hyphen delimited, lowercase selectors: .thisIsBad{}, .this_is_also_bad{} but .this-is-correct{}"? I understand if the point is about the styles itself having hyphens, like padding-bottom, but it breaks the complete expression selection with ctrl+arrows (or even with the double mouse click) which I find much more annoying than using underscores instead of hyphens. I'm biased though, I prefer underscores to camelCase anytime (I do obey whatever is the rule on any project).