/* Skip Link */
.skip-link {
  position: absolute;
  top: -100%;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-primary);
  color: var(--color-background);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-md);
  z-index: 101;
  font-weight: 500;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-2);
}

/* Header Layout */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-gray-200);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 4.5rem;
  gap: var(--space-4);
}

/* Logo */
.site-logo {
  font-family: var(--font-family-heading);
  font-size: var(--font-size-2xl);
  font-weight: 600;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.02em;
  flex-shrink: 0;
}

.site-logo:hover {
  color: var(--color-primary);
}

/* Navigation */
.main-navigation {
  display: flex;
  align-items: center;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-6);
  list-style: none;
}

.nav-link {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: 0.025em;
  padding: var(--space-2) 0;
  position: relative;
  transition: color var(--transition-fast);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--color-accent);
  transition: width var(--transition-base);
}

.nav-link:hover,
.nav-link:focus {
  color: var(--color-primary);
}

.nav-link:hover::after,
.nav-link:focus::after {
  width: 100%;
}

/* Header Actions */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.action-link {
  color: var(--color-text);
  font-size: var(--font-size-lg);
  padding: var(--space-2);
  transition: color var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.action-link:hover {
  color: var(--color-primary);
}

/* Mobile Menu Toggle */
.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 2.5rem;
  height: 2.5rem;
  background: transparent;
  border: none;
  cursor: pointer;
  padding: var(--space-2);
  gap: 5px;
}

.hamburger-line {
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--color-text);
  transition: transform var(--transition-base), opacity var(--transition-base);
  transform-origin: center;
}

/* Mobile Styles */
@media (max-width: 768px) {
  .mobile-menu-toggle {
    display: flex;
  }
  
  .nav-list {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--color-surface);
    flex-direction: column;
    padding: var(--space-4) var(--space-6);
    gap: 0;
    border-bottom: 1px solid var(--color-gray-200);
    box-shadow: var(--shadow-lg);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
  }
  
  .nav-list.is-open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }
  
  .nav-item {
    width: 100%;
    border-bottom: 1px solid var(--color-gray-100);
  }
  
  .nav-item:last-child {
    border-bottom: none;
  }
  
  .nav-link {
    display: block;
    padding: var(--space-4) 0;
    font-size: var(--font-size-base);
  }
  
  .nav-link::after {
    display: none;
  }
  
  /* Hamburger Animation */
  .mobile-menu-toggle[aria-expanded="true"] .hamburger-line:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
  }
  
  .mobile-menu-toggle[aria-expanded="true"] .hamburger-line:nth-child(2) {
    opacity: 0;
  }
  
  .mobile-menu-toggle[aria-expanded="true"] .hamburger-line:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
  }
}