button {
  padding: 8px;
  position: relative;
  font-size: 24px;
  color: #fff;
  border-width: 3px;
  border-bottom-width: 5px;
  border-style: solid;
  border-color: #a8a8a8 #565656 #565656 #a8a8a8;
  outline-width: 2px;
  outline-style: solid;
  outline-color: #000;
  background: url(../img/button.png);
  background-size: cover;
  background-repeat: no-repeat;
  transition: 0.2s transform;
}

button::before {
  content: "";
  position: absolute;
  bottom: -5px;
  left: -3px;
  width: 3px;
  height: 5px;
  background-color: #6d6d6d;
}

button::after {
  content: "";
  position: absolute;
  top: -3px;
  right: -3px;
  width: 3px;
  height: 3px;
  background-color: #6d6d6d;
}

button:hover {
  outline-color: #fff;
}