:is() and :where() in CSS

While browsing web-features’s Baseline data, I found some interesting CSS features. You can download the data and filter like so:

jq '.[] | select(.status.baseline == "high") | .name' < index.json

First, :is() and :where() can be used like :is(.a, .b) .c.

:where() has 0 specificity.

I wonder if :is(), :where(), :not(), :has() can be Turing-complete.