smoothscroll.css

html {
  scroll-behavior: smooth;
}
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}

Found via @netlify repo for https://jamstackconf.com/

Thanks for sharing @zachleat!
I made a quick example of this because I was in disbelief that "smooth scrolling" could be done in pure css.
demo: https://jsfiddle.net/adamculpepper/onu57cpj/5

Per some of the comments on the Tweet https://twitter.com/zachleat/status/1295737380738146304 I’ve switched to using:

@media (prefers-reduced-motion: no-preference) {
  html {
    scroll-behavior: smooth;
  }
}

via https://twitter.com/g16n/status/1296799212445880321 and https://twitter.com/ericwbailey/status/1295741897483464705