1. Cascade layers. With them, we can better manage all the rendering layers on the site. This is the most significant change in CSS since Flex and Grid.
2. Flexbox Gap. The indents between columns are not done through margin and the gaps with a certain distance. But it's instead not a trend but the standard.
3. CSS Container Queries - rethinking how to approach media expressions. Whereas media expressions are based on screen size, Container Queries are based on block size.
P.S. The: has a pseudo-element. Allows you to change CSS depending on whether something is in the element. Small but a very nice thing .