:root {
    --mainColor:#441E4A ;
  }
.nav-link {
    background:
       linear-gradient(
         to bottom, var(--mainColor) 0%,
         var(--mainColor) 100%
       );
      background-position: 0 100%;
      background-repeat: repeat-x;
      background-size: 2px 2px;
    color: #F3B547;
    text-decoration: none;
    transition: background-size .2s;
  }
  
  .nav-link:hover {
    background-size: 4px 50px;
  }