/* カスタム CSS をここに入力してください */

.btn-border-bottom {
  position: relative;
  display: inline-block;
  font-weight: bold;
  padding: 0.25em 0;
  text-decoration: none;
  color: #67c5ff;  
}

.btn-border-bottom:before {
  position: absolute;
  content: '';
  width: 100%;
  height: 4px;
  top:100%;
  left: 0;
  border-radius: 3px;
  background:#67c5ff;
  transition: .2s;
}

.btn-border-bottom:hover:before {
  top: -webkit-calc(100% - 3px);
  top: calc(100% - 3px);
}