If you are creating tabs with pure CSS, the only real reason to do so is for educational purposes, especially considering this is an article about code and not just code.
Then the author decides to use SCSS and some very non-standard flexbox grid layout library... so that nobody can learn from this? Nobody who is just learning CSS will understand SCSS syntax, and nobody wants to learn a new library just to understand an article about CSS.
Ah, I didn't see that button. Looks like it doesn't show up unless you hover over the code which I didn't do. The author really should have mentioned that.
If you are creating tabs with pure CSS, the only real reason to do so is for educational purposes, especially considering this is an article about code and not just code.
Then the author decides to use SCSS and some very non-standard flexbox grid layout library... so that nobody can learn from this? Nobody who is just learning CSS will understand SCSS syntax, and nobody wants to learn a new library just to understand an article about CSS.