button {
  /* font-size: 18px; */
  /* letter-spacing: 2px; */
  /* text-transform: uppercase; */
  display: inline-block;
  text-align: center;
  font-weight: bold;
  padding: 0.7em 2em;
  border: 1px;
  border-radius: 5px;
  position: relative;
  /* box-shadow: 0 2px 10px rgba(0, 0, 0, 0.16), 0 3px 6px rgba(0, 0, 0, 0.1); */
  color: black;
  text-decoration: none;
  transition: 0.3s ease all;
  z-index: 1;
}

button:before {
  transition: 0.5s all ease;
  position: absolute;
  top: 0;
  left: 50%;
  right: 50%;
  bottom: 0;
  opacity: 0;
  content: '';
  background-color: black;
  z-index: -1;
}

button:hover, button:focus {
  color: white;
}

button:hover:before, button:focus:before {
  transition: 0.5s all ease;
  left: 0;
  right: 0;
  opacity: 1;
}

button:active {
  transform: scale(0.9);
}