.site-header {
  background-color: var(--color-background);
  border-bottom: 1px solid var(--color-gray-200);
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: var(--shadow-sm);
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-4) 0;
}

.site-identity {
  font-family: var(--font-family-heading);
  font-size: var(--font-size-xl);
  font-weight: 600;
}

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

.site-logo:hover, .site-logo:focus {
  color: var(--color-accent);
}



.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--spacing-2);
  border-radius: var(--border-radius);
  transition: background-color var(--transition-fast);
}

.nav-toggle:hover, .nav-toggle:focus {
  background-color: var(--color-gray-100);
}

.hamburger {
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--color-text);
  position: relative;
}

.hamburger::before, .hamburger::after {
  content: '';
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--color-text);
  position: absolute;
  transition: all var(--transition-fast);
}

.hamburger::before {
  top: -6px;
}

.hamburger::after {
  top: 6px;
}

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

.nav-menu li a {
  color: var(--color-text);
  font-weight: 500;
  transition: color var(--transition-fast);
}

.nav-menu li a:hover, .nav-menu li a:focus {
  color: var(--color-accent);
}

@media (max-width: 767px) {
  .nav-toggle {
    display: block;
  }

  .nav-menu {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--color-background);
    border: 1px solid var(--color-gray-200);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-lg);
    flex-direction: column;
    padding: var(--spacing-4);
    gap: var(--spacing-3);
    transform: translateY(-10px);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-fast);
  }

  .nav-menu:not([hidden]) {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
    width: 100%;
  }

  .nav-menu[aria-expanded="true"] {
    display: flex;
  }
}