:root {
  --darkBlue: #19313e;
  --cream: #ffe4c4;
  --emerald: #40755e;
  --gold: #956d3c;
  --bronze: #634625;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background-color: var(--darkBlue);
  font-family: sans-serif;
}
ul {
  margin: 0;
  padding: 0;
  display: flex;
}
li {
  list-style: none;
}
a {
  position: relative;
  display: block;
  margin: 0 10px;
  padding: 5px 10px; 
  color: var(--gold);
  font-size: 30px;
  text-decoration: none;
  text-transform: uppercase;
  transition: .5s;
  overflow: hidden;
}
a:before {
  content: '';
  position: absolute;
  width: 100%;
  height: 4px;
  top: 50%;
  transform: translateY(-50%);
  left: -100%;
  background-color: var(--cream);
  transition: .5s;
}
a:hover:before {
  animation: line .25s linear forwards
}
@keyframes line {
  0% {
    left: -100%;
    height: 4px;
  }
  50% {
    left: 0;
    height: 4px;
  }
  100% {
    left: 0;
    height: 100%;
    z-index: -1
  }
}