* {
  font-family: sans-serif;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  background: #1f1f1f;
}
ul {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  display: flex;
  margin: 0;
  padding: 0;
}
ul li {
  list-style: none;
}
ul li a {
  position: relative;
  display: block;
  width: 40px;
  height: 40px;
  font-size: 20px;
  text-align: center;
  line-height: 40px;
  background: #353535;
  color: #565656;
  text-decoration: none;
  margin: 5px;
  border-radius: 4px;
  box-shadow: inset 0 5px 10px rgba(0, 0, 0, 0.1), 0 2px 5px rgba(0, 0, 0, 0.5);
}
ul li a.active,
ul li a:hover {
  color: #fff;
  text-shadow: 0 0 20px rgb(255, 224, 27), 0 0 20px rgb(255, 224, 27),
  0 0 20px rgb(255, 224, 27), 0 0 20px rgb(255, 224, 27),
  0 0 20px rgb(255, 224, 27), 0 0 20px rgb(255, 224, 27),
  0 0 20px rgb(255, 224, 27), 0 0 20px rgb(255, 224, 27);
}