<nav class="radikalwp-hov-underline"><a class="radikalwp-hov-underline-link" href="#">خانه<//a><a class="radikalwp-hov-underline-link is-active" href="#">اسنیپت‌ها<//a><a class="radikalwp-hov-underline-link" href="#">قالب‌ها<//a><a class="radikalwp-hov-underline-link" href="#">وبلاگ<//a><//nav>

.radikalwp-hov-underline {
  display: flex;
  gap: 26px;
  justify-content: center;
}
.radikalwp-hov-underline-link {
  position: relative;
  padding-bottom: 6px;
  font-size: 14px;
  font-weight: 700;
  color: #475569;
  text-decoration: none;
  background-image: linear-gradient(90deg, #6366f1, #a855f7);
  background-repeat: no-repeat;
  background-position: right bottom;
  background-size: 0% 2.5px;
  transition: color .3s ease, background-size .35s cubic-bezier(.25, .8, .3, 1);
}
.radikalwp-hov-underline-link:hover,
.radikalwp-hov-underline-link.is-active { color: #4f46e5; }
.radikalwp-hov-underline-link:hover,
.radikalwp-hov-underline-link.is-active { background-size: 100% 2.5px; }