nav {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
}

ul {
  list-style-type: none;
  padding: 0;
  margin: 0;
}

li {
  display: inline-block;
  
}

li a {
  text-align: center;
  background-color: #33FF99;
  padding: 5px;
  margin: 0;
  border: 1px solid #000000;
}

li a:hover {
  background-color: #AA80FF;
}