CSS Grid Periodic Table

My attempt to learn CSS Grid by creating a periodic table of elements using CSS Grid Layout.

HTML structure

All elements of the periodic table are in <div> elements inside a <section>. There are 119 HTML elements in total (118 elements + an <aside> for the legend contents).

There are no wrapping elements for periods (rows) and groups (columns). The purpose of this is to produce the desired layout using CSS Grid Layout.