/* 顶部菜单：悬停仅变翠绿 + 下方翠绿横线；选中项常驻 */
.nav-link{
  position: relative;
  text-decoration: none;
}
.nav-link:hover{
  color: #10b981; /* emerald */
}
.nav-link::after{
  content: "";
  position: absolute;
  left: 0.3em;
  right: 0.3em;
  bottom: 0.1em;
  height: 2px;
  background-color: transparent;
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform .18s ease, background-color .18s ease;
}
.nav-link:hover::after{
  background-color: #10b981;
  transform: scaleX(1);
}
/* 选中态（建议在当前菜单加 nav-link--active） */
.nav-link--active{
  color: #10b981 !important;
}
.nav-link--active::after{
  background-color: #10b981;
  transform: scaleX(1);
}