footer {
  margin-block-start: 300vb;
  text-align: center;
  padding: 3rem;
  font-size: 20cqi;
  timeline-trigger-name: --t;
  timeline-trigger-source: view();
}

footer span {
  display: inline-block;
  animation: wave 1s ease forwards;
  animation-trigger: --t play-forwards;
}

@keyframes wave {
  0% {
    rotate: 0deg;
  }
  20% {
    rotate: -20deg;
  }
  40% {
    rotate: 20deg;
  }
  60% {
    rotate: -20deg;
  }
  80% {
    rotate: 20deg;
  }
  100% {
    rotate: 0deg;
  }
}