Ahmad Shadeed covers the idea of a card component that has a fixed set of semantic HTML with some BEMy classes on it. There is a title, author, image, and tags. Then he redesigns the card into five totally different designs without touching any of the HTML just the CSS.
If this is an ah-ha moment for you, awesome! It might be worth knowing that this exact concept essentially excited an entire generation of front-end developers, in no small part due to the concept of the CSS Zen Garden, where the entire website was a fixed set of HTML and only CSS changes birthed some incredible creativity.