.site-header {
  background-color: var(--bg-color);
  border-bottom: 1px solid var(--secondary);
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: var(--shadow-sm);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 80px;
}

.site-logo {
  font-family: var(--font-serif);
  font-size: var(--text-2xl);
  color: var(--primary);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

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

.main-nav-list {
  display: flex;
  gap: var(--space-6);
  list-style: none;
  margin: 0;
  padding: 0;
}

.main-nav-link {
  color: var(--text-color);
  font-weight: 500;
  font-size: var(--text-sm);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  position: relative;
}

.main-nav-link::after {
  content: '';
  position: absolute;
  width: 0%;
  height: 2px;
  bottom: -4px;
  left: 0;
  background-color: var(--primary);
  transition: width var(--transition-base);
}

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

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

.mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--primary);
  font-size: var(--text-2xl);
  cursor: pointer;
  padding: var(--space-2);
  transition: color var(--transition-fast);
}

.mobile-menu-toggle:hover {
  color: var(--primary-hover);
}

@media (max-width: 768px) {
  .mobile-menu-toggle {
    display: block;
  }
  
  .main-nav {
    position: absolute;
    top: 80px;
    left: 0;
    right: 0;
    background-color: var(--surface-color);
    border-bottom: 1px solid var(--gray-800);
    padding: var(--space-6) var(--space-4);
    transform: translateY(-150%);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
  }
  
  .main-nav.is-open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
    box-shadow: var(--shadow-md);
  }
  
  .main-nav-list {
    flex-direction: column;
    align-items: center;
    gap: var(--space-4);
  }
}