view-transitions-api.css

@import "https://unpkg.com/open-props/easings.min.css";
@import "https://unpkg.com/open-props/animations.min.css";

body {
  min-block-size: 100vh;
  font-family: system-ui, sans-serif;
  display: grid;
  place-content: center;
  place-items: center;
}

html {
  color-scheme: dark light;
}

h1.container {
  view-transition-name: fade;
}

@media (prefers-reduced-motion: no-preference) {

  ::view-transition-old(fade) {
    animation:
      var(--animation-fade-out),
      var(--animation-scale-down);
  }

  ::view-transition-new(fade) {
    animation:
      var(--animation-fade-out) reverse,
      var(--animation-slide-in-up);
  }
}


h1.container {
  inline-size: 100vw;
  font-size: 30vmin;
  text-align: center;
  margin: 0;
  view-transition-name: fade;
}

@keyframes fade-in {
  0% {
    opacity: 0;
  }

  100% {
    opacity: 1;
  }
}


@keyframes fade-out {
  0% {
    opacity: 1;
  }

  100% {
    opacity: 0;
  }
}