.wave span {
  display: inline-block;
  animation: wave 1.5s  3 ease-in-out;
  animation-delay: calc(var(--i) * 0.1s);
  font-weight: bold;
  font-size: 2rem;
}


@keyframes wave {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-7px); }
}