/* ========================================
   Header & Navigation Styles
   ======================================== */

   header {
    text-align: center;
    margin-bottom: var(--space-lg);
    padding-bottom: var(--space-md);
    border-bottom: 2px solid var(--color-border-light);
  }
  
  .header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--space-md);
  }
  
  .logo-link {
    display: inline-block;
    transition: opacity var(--transition-fast);
  }
  
  .logo-link:hover {
    opacity: 0.8;
  }
  
  .logo-container {
    display: inline-block;
  }
  
  .logo {
    max-width: 200px;
    height: auto;
  }
  
  .tagline {
    color: var(--color-text-secondary);
    font-size: var(--font-size-body);
    margin: var(--space-sm) 0 0 0;
  }
  
  /* Desktop Navigation */
  .main-nav {
    display: flex;
    align-items: center;
    gap: var(--space-md);
  }
  
  .nav-link {
    color: var(--color-text-primary);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
    padding: var(--space-xs) var(--space-sm);
    border-radius: var(--radius-sm);
    transition: background-color var(--transition-fast), color var(--transition-fast);
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    cursor: pointer;
    background: none;
    border: none;
    font-family: var(--font-primary);
    font-size: var(--font-size-body);
  }
  
  .nav-link:hover {
    background-color: var(--color-bg-light);
    color: var(--color-primary-dark);
  }
  
  /* Dropdown */
  .nav-dropdown {
    position: relative;
  }
  
  .dropdown-toggle {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
  }
  
  .chevron-down {
    transition: transform var(--transition-fast);
  }
  
  .nav-dropdown.active .chevron-down {
    transform: rotate(180deg);
  }
  
  .dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    margin-top: var(--space-xs);
    background: white;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-lg);
    min-width: 220px;
    z-index: 1000;
    display: none;
    opacity: 0;
    transform: translateY(-10px);
    transition: opacity var(--transition-fast), transform var(--transition-fast);
  }
  
  .nav-dropdown.active .dropdown-menu {
    display: block;
    opacity: 1;
    transform: translateY(0);
  }
  
  .dropdown-item {
    display: block;
    padding: var(--space-sm) var(--space-md);
    color: var(--color-text-primary);
    text-decoration: none;
    transition: background-color var(--transition-fast);
    border-bottom: 1px solid var(--color-border-light);
  }
  
  .dropdown-item:last-child {
    border-bottom: none;
  }
  
  .dropdown-item:hover {
    background-color: var(--color-bg-light);
    color: var(--color-primary-dark);
  }
  
  /* Mobile Menu Toggle */
  .mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-xs);
    color: var(--color-text-primary);
  }
  
  /* Mobile Navigation */
  .mobile-nav {
    display: none;
    flex-direction: column;
    margin-top: var(--space-md);
    padding-top: var(--space-md);
    border-top: 1px solid var(--color-border-light);
  }
  
  .mobile-nav.active {
    display: flex;
  }
  
  .mobile-nav-link {
    padding: var(--space-sm) var(--space-md);
    color: var(--color-text-primary);
    text-decoration: none;
    border-radius: var(--radius-sm);
    transition: background-color var(--transition-fast);
  }
  
  .mobile-nav-link:hover {
    background-color: var(--color-bg-light);
  }
  
  .mobile-nav-section {
    margin-top: var(--space-sm);
  }
  
  .mobile-nav-header {
    padding: var(--space-xs) var(--space-md);
    font-weight: var(--font-weight-bold);
    color: var(--color-text-secondary);
    font-size: var(--font-size-small);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin: var(--space-xs) 0;
  }
  
  /* Help Links in Calculator */
  .help-link-intro {
    margin-top: var(--space-sm);
    font-size: var(--font-size-small);
    color: var(--color-text-secondary);
  }
  
  .help-link-intro a {
    color: var(--color-primary-dark);
    font-weight: var(--font-weight-medium);
    text-decoration: none;
  }
  
  .help-link-intro a:hover {
    color: var(--color-accent);
    text-decoration: underline;
  }
  
  .help-link {
    display: block;
    margin-top: var(--space-xs);
    font-size: var(--font-size-small);
    color: var(--color-text-secondary);
  }
  
  .help-link a {
    color: var(--color-primary-dark);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
  }
  
  .help-link a:hover {
    color: var(--color-accent);
    text-decoration: underline;
  }
  
  /* Responsive */
  @media (max-width: 768px) {
    .header-content {
      flex-direction: column;
      gap: var(--space-md);
    }
  
    .main-nav {
      display: none;
    }
  
    .mobile-menu-toggle {
      display: block;
      position: absolute;
      top: var(--space-md);
      right: var(--space-md);
    }
  
    .logo {
      max-width: 150px;
    }
  
    .dropdown-menu {
      position: static;
      box-shadow: none;
      border: none;
      margin-top: 0;
      border-top: 1px solid var(--color-border-light);
    }
  }