nav {
  background-color: #333;
  padding: 0;
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
}

nav li {
  position: relative;
}

nav a {
  display: block;
  padding: 15px 20px;
  color: white;
  text-decoration: none;
  transition: background-color 0.3s ease;
}

nav a:hover,
nav a.active {
  background-color: #007bff;
}

nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: white;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

/* Parent item */
nav li {
  position: relative;
}

/* Dropdown container */
nav ul ul {
  position: absolute;
  top: 100%;
  left: 0;
  min-width: 200px;
  display: none;
  flex-direction: column;
  background-color: #444;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
}

/* Show on hover */
nav li:hover > ul {
  display: flex;
}

/* Dropdown items */
nav ul ul a {
  padding: 10px 15px;
}

nav ul ul a:hover {
  background-color: #555;
}

.menu-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 24px;
  cursor: pointer;
  padding: 15px;
}

@media (max-width: 768px) {
  .menu-toggle {
    display: block;
  }
  
  nav ul {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: #333;
  }
  
  nav ul.active {
    display: flex;
  }
  
  nav li {
    width: 100%;
  }
}

.nav-search {
  margin-left: auto;
  padding: 5px;
}

.nav-search input {
  padding: 8px 15px;
  border: none;
  border-radius: 20px;
  outline: none;
}

nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
}

.logo {
  font-size: 24px;
  font-weight: bold;
  color: white;
}

.nav-links {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
}

.mega-menu {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background-color: white;
  display: none;
  padding: 30px;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.has-mega:hover .mega-menu {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 30px;
}

.tabs {
  display: flex;
  border-bottom: 2px solid #ddd;
}

.tab {
  padding: 15px 30px;
  cursor: pointer;
  border: none;
  background: none;
  border-bottom: 3px solid transparent;
  transition: all 0.3s ease;
}

.tab:hover {
  background-color: #f8f9fa;
}

.tab.active {
  border-bottom-color: #007bff;
  color: #007bff;
}

.sidenav {
  width: 250px;
  height: 100vh;
  position: fixed;
  left: 0;
  top: 0;
  background-color: #2c3e50;
  padding: 20px 0;
  overflow-y: auto;
}

.sidenav a {
  display: block;
  padding: 15px 25px;
  color: white;
  text-decoration: none;
  transition: background-color 0.3s ease;
}

.sidenav a:hover,
.sidenav a.active {
  background-color: #34495e;
  border-left: 4px solid #007bff;
}

.breadcrumb {
  display: flex;
  list-style: none;
  padding: 10px 0;
  margin: 0;
}

.breadcrumb li + li::before {
  content: '/';
  padding: 0 10px;
  color: #6c757d;
}

.breadcrumb a {
  color: #007bff;
  text-decoration: none;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

<nav aria-label="Main navigation">
  <button aria-label="Toggle menu" aria-expanded="false">Menu</button>
  <ul>
    <li><a href="/" aria-current="page">Home</a></li>
    <li><a href="/about">About</a></li>
  </ul>
</nav>