Drupal+Zen+SMACSS (tears, rage, confusion)

Today I downloaded the latest version of Zen (5.4) and did not find the usual CSS files in it. It turns out that the theme has been transitioned to a new organizational structure for CSS called SMACSS and it may also be included (or already is?) in Drupal 8.

As a beginner (which I am), encountering this method of organization presents serious challenges. There is almost no information available in Russian about it (I found one poor note). I've been digging into this for a day and can't grasp the clear rules or the structure of CSS organization.

Could someone explain the essence of this structure in simple terms, how to categorize elements, etc.? And if Ivan could make a video tutorial, this material would be invaluable in the Russian-speaking web.

ps The strikethrough feature doesn't work on the forum. test