.button {
  -webkit-box-flex: 1;
      -ms-flex: 1 1 auto;
          flex: 1 1 auto;
  margin: 10px;
  padding: 20px;
  border: 2px solid #34D8B9;
  text-align: center;
  text-transform: uppercase;
  position: relative;
  overflow: visible;
  -webkit-transition: .3s;
  transition: .3s;
}
.button:after {
  position: absolute;
  -webkit-transition: .3s;
  transition: .3s;
  content: '';
  width: 0;
  left: 50%;
  bottom: 0;
  height: 3px;
  background: #538CB4;background: linear-gradient(135deg,#538CB4 30%,#39dfaa 100%);
}
.button.left:after {
  left: 0;
}
.button.left-right:after {
  right: 0;
  left: auto;
}
.button:hover {
  cursor: pointer;
}
.button:hover:after {
  width: 100%;
  left: 0;
}
.button:.fill {
  color: #5bcaff;
}
.button.fill:after {
  left: -10%;
  width: 120%;
}
.button.round {
  border-radius: 30px;
}
.button.round:after {
  width: 0%;
}