@import url(https://fonts.googleapis.com/css?family=Raleway:400,500,800);

body {
  background-color: #333;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: "Raleway", Arial, sans-serif;
}
ul {
  padding: 0;
  display: flex;
}

ul li {
  list-style: none;
  padding: 10px 40px;
}

ul li a {
  text-decoration: none;
  text-transform: uppercase;
  font-size: 24px;
  color: white;
  position: relative;
  padding: 5px;
}

a:hover {
  color: #ff0;
}

span:first-child:before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 8px;
  height: 8px;
  background-color: transparent;
  border-top: 2px solid #ff0;
  border-left: 2px solid #ff0;
  transition: 0.2s;
  opacity: 0;
}

span:first-child:after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: 8px;
  height: 8px;
  background-color: transparent;
  border-top: 2px solid #ff0;
  border-right: 2px solid #ff0;
  transition: 0.2s;
  opacity: 0;
}

span:last-child:before {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 8px;
  height: 8px;
  background-color: transparent;
  border-bottom: 2px solid #ff0;
  border-left: 2px solid #ff0;
  transition: 0.2s;
  opacity: 0;
}

span:last-child:after {
  content: "";
  position: absolute;
  bottom: 0;
  right: 0;
  width: 8px;
  height: 8px;
  background-color: transparent;
  border-bottom: 2px solid #ff0;
  border-right: 2px solid #ff0;
  transition: 0.2s;
  opacity: 0;
}

a:hover span:first-child:before {
  top: -10px;
  left: -10px;
  opacity: 1;
}

a:hover span:first-child:after {
  top: -10px;
  right: -10px;
  opacity: 1;
}

a:hover span:last-child:before {
  bottom: -10px;
  left: -10px;
  opacity: 1;
}

a:hover span:last-child:after {
  bottom: -10px;
  right: -10px;
  opacity: 1;
}