how to start a animation on scroll code example

Example 1: animation on scroll css

svg {
  position: fixed; /* make sure it stays put so we can see it! */

  animation: rotate 1s linear infinite;
  /*animation-play-state: paused;*/
  animation-delay: calc(var(--scroll) * -1s);
}

Example 2: scrolling animation css

.inline-photo {
  border: 1em solid #fff;
  border-bottom: 4em solid #fff;
  border-radius: .25em;
  box-shadow: 1em 1em 2em .25em rgba(0,0,0,.2);
  margin: 2em auto;
  opacity: 0;
  transform: translateY(4em) rotateZ(-5deg);
  transition: transform 4s .25s cubic-bezier(0,1,.3,1),
              opacity .3s .25s ease-out;
  max-width: 600px;
  width: 90%;
  will-change: transform, opacity;
}