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

.radikalwp-nav-underline { display: flex; gap: 26px; }
.radikalwp-nav-underline-a {
  position: relative; font-size: 14px; font-weight: 700; color: #475569; text-decoration: none; padding-bottom: 6px;
}
.radikalwp-nav-underline-a::after {
  content: ""; position: absolute; bottom: 0; right: 0; height: 2.5px; width: 0; border-radius: 99px;
  background: #4f46e5; transition: width .3s ease;
}
.radikalwp-nav-underline-a:hover::after, .radikalwp-nav-underline-a.is-active::after { width: 100%; }
.radikalwp-nav-underline-a.is-active { color: #4f46e5; }