.button {
  display: inline-block;
  margin-top: 10%;
  padding: 1em 2em;
  font-size: 2em;
  color: #fff;
  font-family: arial, sans-serif;
  text-decoration: none;
  border-radius: 0.3em;
  position: relative;
  background-color: #ccc;
  background-image: linear-gradient(to top, #6d8aa0, #8ba2b4);
  -webkit-backface-visibility: hidden;
  z-index: 1;
}
.button:after {
  position: absolute;
  content: '';
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border-radius: 0.3em;
  background-image: linear-gradient(to top, #ca5f5e, #d68584);
  transition: opacity 0.5s ease-out;
  z-index: 2;
  opacity: 0;
}
.button:hover:after {
  opacity: 1;
}
.button span {
  position: relative;
  z-index: 3;
}
body {
  text-align: center;
  background: #ddd;
}