<button class="cp_button13">button</button>

.cp_button13 {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  width: 160px;
  padding: 1em;
  cursor: pointer;
  color: #2e7d32;
  background: #d4e157;
  border: 0;
  border-radius: 0;
  transition: transform 0.3s;
  z-index: 1;
}
.cp_button13:before {
  position: absolute;
  top: 100%;
  left: 5%;
  content: '';
  width: 90%;
  height: 10px;
  transition:transform 0.3s,opacity 0.3s;
  background: radial-gradient(ellipse at center, rgba(46,125,50, 0.35) 0%, rgba(46,125,50, 0) 80%);
  opacity: 0;
  z-index: -1;
}
.cp_button13:hover {
  transform: translateY(-6px);
  animation: button13 1.5s linear infinite alternate 0.3s;
  color: #2e7d32;
}
.cp_button13:hover:before {
  transform: translateY(6px);
  animation: button13_shadow 1.5s linear infinite alternate 0.3s;
  opacity: 0.4;
}
/*アニメーションの設定*/
@keyframes button13 {
  50% { transform: translateY(-3px);}
  100% { transform: translateY(-6px);}
}
@keyframes button13_shadow {
    0% { transform: translateY(6px); opacity: 0.4;}
  50% { transform: translateY(3px); opacity: 1;}
  100% { transform: translateY(6px); opacity: 0.4;}
}