ぽよよん

↓HTML

<div class="poyoyon">
  <p>ぽよよん</p>
</div>

↓CSS

.poyoyon{
  animation: poyoyon 1s ease-in-out forwards;
}
 
@keyframes poyoyon {
  0%  {
    transform: scale(1.0, 1.0) translate(0, 0);
  }
  15% {
    transform: scale(0.98, 0.9) translate(0, 5px);
  }
  30% {
    transform: scale(1.02, 1.0) translate(0, 8px);
  }
  50% {transform: scale(0.98, 1.05) translate(0, -8px);
  }
  70% {
    transform: scale(1.0, 0.9) translate(0, 5px);
  }
  100% {
    transform: scale(1.0, 1.0) translate(0, 0);
  }
  0%, 100% {
    opacity: 1;
  }
}