How do pseudo classes work in Sass?

Question

Sass

In the main.sass document, I can't figure out how to apply the first-child or nth-child pseudo-class .
&:hover, active, focus , etc. are great.

Answer 1

&:first-child, &:nth-child(1)

Answer 2

Everything is working

&:first-child { ... }
&:nth-child(2n) { ... }

Example https://codepen.io/AXP/pen/PKwOQo