.topnav li a {
  transition: 0.3s ease;
  border-top: 4px solid #999 !important;
  border-bottom: 4px solid #999 !important;
  padding: 20px 0;
  margin: 0 20px;
}

.topnav li a:hover {
  border-top: 4px solid #ffffff !important;
  border-bottom: 4px solid #ffffff !important;
  padding: 6px 0;
}