Some “vertical rhythm” using horizontal grids. What a pain in the ass:
You have to carefully choose the font-sizes and line-heights so that all the content on the page lines up on the grid. So if the base font size is 16px, and a headline is 21px, and you have to make all of that fit on a constant 24px line-height, then the headline needs to span multiple lines (breaking rhythm within itself) but magically aligns back into the grid. This means setting a parent line-height to a multiple of 24px, vertical centering (which is of course complete shady bs unless you use all-caps and have a consistent font height).
Typesetting is annoying and really poorly explained in tutorials online.
Typical tutorials seems to start with “here is the x-height, serifs, sans-serifs, … bam beautiful” few take the time to expand on the relationship between x-height, the vertical centering algorithm, and how that fits into “vertical rhythm.” I guess I’m just spoiled by programming which logically explains all theory and implementation details from start to finish.