.sunken-button {
 color: #090909;
  padding: 0.7em 1.7em;
  margin-left: 10px;
  margin-right: 10px;
  margin: 5px;
  font-size: 12px;
  border-radius: 0.5em;
  background: #e8e8e8;
  cursor: pointer;
  border: 1px solid #e8e8e8;
  transition: all 0.3s;
  box-shadow: 6px 6px 12px #c5c5c5, -6px -6px 12px #ffffff;
}

.sunken-button:active {
 color: #666;
  box-shadow: inset 4px 4px 12px #c5c5c5, inset -4px -4px 12px #ffffff;
}