button {
  padding: 20px 60px;
  background-color: #000;
  border: none;
  font-size: 18px;
  position: relative;
  /* overflow: hidden; */
  transition: 500ms;
}

button span {
  color: gray;
  position: relative;
  transition: 500ms;
  transition-delay: 500ms;
  font-size: 16px;
  text-transform: uppercase;
  letter-spacing: 2px;
  font-weight: 600;
}

button:before {
  content: '';
  position: absolute;
  width: 0%;
  height: 0%;
  left: 50%;
  right: 50%;
  top: 50%;
  bottom: 50%;
  transition: 500ms;
  transition-delay: 500ms;
  background-color: red;
  box-shadow: 0 0 10px red,
   0 0 30px red, 
   0 0 50px red;
}

button div {
  transition: 500ms;
  position: absolute;
  background-color: red;
  box-shadow: 0 0 15px red, 0 0 30px red, 0 0 50px red;
}

button .top {
  width: 15px;
  height: 2px;
  top: 0;
  left: 0;
}

button .bottom {
  width: 15px;
  height: 2px;
  bottom: 0;
  right: 0;
}

button .left {
  width: 2px;
  height: 15px;
  top: 0;
  left: 0;
}

button .right {
  width: 2px;
  height: 15px;
  bottom: 0;
  right: 0;
}

button:hover {
  color: #000;
}

button:hover span {
  color: #000;
}

button:hover:before {
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
}

button:hover .top, 
button:hover .bottom {
  width: 100%;
}

button:hover .left,
button:hover .right {
  height: 100%;
}