Bootstrap 5 Navbar with Hover Fill Animation

<section class="wdw-stage">
  <div class="container" style="max-width: 1040px">
    <div class="wdw-card overflow-hidden">
      <nav class="navbar navbar-expand-md px-3 px-md-4 py-3 bg-body" aria-label="Main">
        <a class="navbar-brand d-flex align-items-center gap-2 fw-bold text-body-emphasis" href="#">
          <span class="wdw-icon" style="width:2.25rem;height:2.25rem;border-radius:.65rem"><svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="m12 3 9 5-9 5-9-5zM3 13l9 5 9-5"/></svg></span>
          Northwind
        </a>
        <button class="navbar-toggler border-0" type="button" data-bs-toggle="collapse" data-bs-target="#mainMenu" aria-controls="mainMenu" aria-expanded="false" aria-label="Toggle navigation">
          <span class="navbar-toggler-icon"></span>
        </button>
        <div class="collapse navbar-collapse" id="mainMenu">
          <ul class="navbar-nav mx-auto gap-1 py-3 py-md-0" id="menu-links"><li class="nav-item"><a class="nav-link menu-fill active" aria-current="page" href="#">Home</a></li><li class="nav-item"><a class="nav-link menu-fill" href="#">About</a></li><li class="nav-item"><a class="nav-link menu-fill is-hover" href="#">Clients</a></li><li class="nav-item"><a class="nav-link menu-fill" href="#">Search us</a></li><li class="nav-item"><a class="nav-link menu-fill" href="#">Contact us</a></li></ul>
          <a class="btn btn-primary rounded-pill px-4" href="#">Get started</a>
        </div>
      </nav>
      <div class="wdw-aurora px-4 px-md-5 py-4 py-md-5">
        <div class="row align-items-center g-4 py-md-3">
          <div class="col-md-6">
            <span class="badge rounded-pill bg-white bg-opacity-10 text-white border border-white border-opacity-25 mb-3 px-3 py-2">Hover the menu</span>
            <h1 class="h2 fw-bold mb-3" style="letter-spacing:-.02em">Menus that respond to the pointer</h1>
            <p class="mb-0 opacity-75">Each item fills from the bottom on hover, so the target feels solid and clear.</p>
          </div>
          <div class="col-md-6 d-none d-md-block">
            <div class="rounded-4 p-4 bg-white bg-opacity-10 border border-white border-opacity-25">
              <div class="d-flex justify-content-between align-items-center mb-3">
                <span class="fw-semibold">Active clients</span><span class="small opacity-75">This month</span>
              </div>
              <div class="display-6 fw-bold mb-3">128</div>
              <div class="progress bg-white bg-opacity-25 mb-2" style="height:.5rem" role="progressbar" aria-label="Onboarding" aria-valuenow="72" aria-valuemin="0" aria-valuemax="100"><div class="progress-bar bg-white" style="width:72%"></div></div>
              <div class="small opacity-75">72% onboarded</div>
            </div>
          </div>
        </div>
      </div>
    </div>
  </div>
</section>

/* Web Designer Wall library style — shared base for every Bootstrap 5 snippet.
   Indigo accent, Plus Jakarta Sans, soft cards, pill buttons. Works in light and dark. */
@import url("https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&display=swap");

:root,
[data-bs-theme="light"] {
  --wdw-font: "Plus Jakarta Sans", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --bs-body-font-family: var(--wdw-font);
  --bs-primary: #4f46e5;
  --bs-primary-rgb: 79, 70, 229;
  --bs-primary-text-emphasis: #3730a3;
  --bs-primary-bg-subtle: #eef2ff;
  --bs-primary-border-subtle: #c7d2fe;
  --bs-link-color: #4f46e5;
  --bs-link-color-rgb: 79, 70, 229;
  --bs-link-hover-color: #4338ca;
  --bs-link-hover-color-rgb: 67, 56, 202;
  --bs-focus-ring-color: rgba(79, 70, 229, 0.25);
  --bs-border-radius: 0.75rem;
  --bs-border-radius-lg: 1rem;
  --bs-border-radius-xl: 1.25rem;
  --wdw-radius-card: 1.25rem;
  --wdw-shadow: 0 1px 2px rgba(16, 24, 40, 0.05), 0 16px 40px -16px rgba(16, 24, 40, 0.22);
  --wdw-shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06), 0 4px 12px -4px rgba(16, 24, 40, 0.12);
  --wdw-stage: #f5f6fb;
}

[data-bs-theme="dark"] {
  --bs-primary: #818cf8;
  --bs-primary-rgb: 129, 140, 248;
  --bs-primary-text-emphasis: #c7d2fe;
  --bs-primary-bg-subtle: rgba(129, 140, 248, 0.14);
  --bs-primary-border-subtle: rgba(129, 140, 248, 0.35);
  --bs-link-color: #a5b4fc;
  --bs-link-color-rgb: 165, 180, 252;
  --bs-link-hover-color: #c7d2fe;
  --bs-link-hover-color-rgb: 199, 210, 254;
  --bs-focus-ring-color: rgba(129, 140, 248, 0.35);
  --wdw-shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 16px 40px -16px rgba(0, 0, 0, 0.7);
  --wdw-shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4), 0 4px 12px -4px rgba(0, 0, 0, 0.5);
  --wdw-stage: #0f1117;
}

body { font-family: var(--wdw-font); -webkit-font-smoothing: antialiased; }

/* Bootstrap compiles its blue into these components; point them at the accent. */
.btn-primary {
  --bs-btn-bg: var(--bs-primary); --bs-btn-border-color: var(--bs-primary);
  --bs-btn-hover-bg: #4338ca; --bs-btn-hover-border-color: #4338ca;
  --bs-btn-active-bg: #3730a3; --bs-btn-active-border-color: #3730a3;
  --bs-btn-disabled-bg: var(--bs-primary); --bs-btn-disabled-border-color: var(--bs-primary);
  --bs-btn-focus-shadow-rgb: var(--bs-primary-rgb);
}
[data-bs-theme="dark"] .btn-primary { --bs-btn-color: #0f1117; --bs-btn-hover-bg: #a5b4fc; --bs-btn-hover-border-color: #a5b4fc; --bs-btn-hover-color: #0f1117; --bs-btn-active-color: #0f1117; }
.btn-outline-primary {
  --bs-btn-color: var(--bs-primary); --bs-btn-border-color: var(--bs-primary);
  --bs-btn-hover-bg: var(--bs-primary); --bs-btn-hover-border-color: var(--bs-primary);
  --bs-btn-active-bg: var(--bs-primary); --bs-btn-active-border-color: var(--bs-primary);
  --bs-btn-focus-shadow-rgb: var(--bs-primary-rgb);
}
.btn { --bs-btn-font-weight: 600; min-height: 44px; display: inline-flex; align-items: center; justify-content: center; gap: .5rem; }
.btn-sm { min-height: 36px; }
.form-control, .form-select { min-height: 44px; border-radius: .75rem; }
.form-control:focus, .form-select:focus, .form-check-input:focus { border-color: rgba(var(--bs-primary-rgb), .6); box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.form-check-input:checked { background-color: var(--bs-primary); border-color: var(--bs-primary); }
.nav-pills { --bs-nav-pills-link-active-bg: var(--bs-primary); }
.nav { --bs-nav-link-color: var(--bs-secondary-color); --bs-nav-link-hover-color: var(--bs-emphasis-color); }
.pagination { --bs-pagination-active-bg: var(--bs-primary); --bs-pagination-active-border-color: var(--bs-primary); --bs-pagination-color: var(--bs-body-color); --bs-pagination-focus-box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.progress, .progress-stacked { --bs-progress-bar-bg: var(--bs-primary); }
.list-group { --bs-list-group-active-bg: var(--bs-primary); --bs-list-group-active-border-color: var(--bs-primary); }
.dropdown-menu { --bs-dropdown-link-active-bg: var(--bs-primary); border-radius: .875rem; box-shadow: var(--wdw-shadow-sm); }
.accordion { --bs-accordion-active-bg: var(--bs-primary-bg-subtle); --bs-accordion-active-color: var(--bs-primary-text-emphasis); --bs-accordion-btn-focus-box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.badge { font-weight: 600; }

/* Library building blocks — use these instead of re-inventing them per snippet. */
.wdw-stage { min-height: 100vh; display: flex; align-items: center; background: var(--wdw-stage); padding-block: 3rem; }
.wdw-card { background: var(--bs-body-bg); border: 1px solid var(--bs-border-color-translucent); border-radius: var(--wdw-radius-card); box-shadow: var(--wdw-shadow); }
.wdw-card-sm { background: var(--bs-body-bg); border: 1px solid var(--bs-border-color-translucent); border-radius: 1rem; box-shadow: var(--wdw-shadow-sm); }
.wdw-aurora { position: relative; color: #fff; background: radial-gradient(60% 55% at 100% 0, #818cf8 0, transparent 70%), radial-gradient(65% 60% at 0 100%, #ec4899 0, transparent 65%), #1e1b4b; }
.wdw-eyebrow { display: inline-block; font-size: .75rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--bs-primary); }
.wdw-heading { font-weight: 800; letter-spacing: -.02em; color: var(--bs-emphasis-color); }
.wdw-muted { color: var(--bs-secondary-color); }
.wdw-icon { width: 2.75rem; height: 2.75rem; flex: none; display: inline-flex; align-items: center; justify-content: center; border-radius: .875rem; background: var(--bs-primary-bg-subtle); color: var(--bs-primary); }

/* Component */
.navbar .navbar-nav .nav-link.menu-fill {
  position: relative; border-radius: 999px; padding: .6rem 1.1rem; font-weight: 600; text-decoration: none;
  color: var(--bs-secondary-color);
  background: linear-gradient(var(--bs-primary-bg-subtle), var(--bs-primary-bg-subtle)) no-repeat 0 100% / 100% 0;
  transition: background-size .3s ease, color .2s ease;
}
.navbar .navbar-nav .nav-link.menu-fill:hover, .navbar .navbar-nav .nav-link.menu-fill:focus-visible, .navbar .navbar-nav .nav-link.menu-fill.is-hover { background-size: 100% 100%; color: var(--bs-primary-text-emphasis); }
.navbar .navbar-nav .nav-link.menu-fill.active { color: var(--bs-primary-text-emphasis); background-size: 100% 100%; }
.menu-fill.active::after { content: ""; position: absolute; left: 50%; bottom: .3rem; width: 1rem; height: 2px; margin-left: -.5rem; border-radius: 2px; background: var(--bs-primary); }
@media (prefers-reduced-motion: reduce) { .navbar .navbar-nav .nav-link.menu-fill { transition: none; } }
@media (max-width: 767.98px) { .navbar .navbar-nav .nav-link.menu-fill { border-radius: .75rem; } .menu-fill.active::after { left: 1.1rem; margin-left: 0; } }

(function () {
  function initMenuActive() {
    var links = document.querySelectorAll('#menu-links .nav-link');
    if (!links.length) return;
    links.forEach(function (a) {
      a.addEventListener('click', function (e) {
        e.preventDefault();
        links.forEach(function (o) { o.classList.remove('active'); o.removeAttribute('aria-current'); });
        a.classList.add('active');
        a.setAttribute('aria-current', 'page');
      });
    });
  }
  initMenuActive();
})();