A page like any other

Set a line of text in a button and centre it vertically.

It is sitting slightly high, and no amount of padding will fix it, because the thing you centred is not the thing you are looking at.

Every font reserves a band of empty space above its capitals and another below its baseline for descenders, and those two bands are almost never the same size. The browser measures the font's box, subtracts it from the line height, and splits what is left equally.

So it centres the box perfectly. The letters inside that box were never centred.

Nothing here is a mistake

The type on this page is set with a fluid scale, a spacing scale in round numbers, and leading expressed as a ratio. Every one of those is a reasonable decision, and together they produce a page with rhythm and no phase.

28.35 is not a whole number of anything. Every line below the first inherits the fraction, and by the fifth it is visible.