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

.site-identity a {
  transition: color var(--transition-fast);
}

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

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

.nav-list a {
  color: var(--color-text);
  font-weight: 600;
  padding: var(--spacing-2) var(--spacing-4);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast), color var(--transition-fast);
}

.nav-list a:hover,
.nav-list a:focus {
  background-color: var(--color-neutral-100);
  color: var(--color-primary);
}

.hamburger-btn {
  background: none;
  border: none;
  color: var(--color-text);
  font-size: var(--font-size-xl);
  cursor: pointer;
  padding: var(--spacing-2);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
}

.hamburger-btn:hover,
.hamburger-btn:focus {
  background-color: var(--color-neutral-100);
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.nav-list[aria-hidden="true"] {
  display: none;
}

.nav-list[aria-hidden="false"] {
  display: flex;
}

@media (max-width: 768px) {
  .hamburger-btn {
    display: block;
  }

  .nav-list {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--color-background);
    border: 1px solid var(--color-neutral-200);
    box-shadow: var(--shadow-md);
    flex-direction: column;
    padding: var(--spacing-4);
    aria-hidden: true;
    display: none;
  }

  .nav-list[aria-hidden="false"] {
    display: flex;
  }

  .nav-list a {
    padding: var(--spacing-3) 0;
    border-bottom: 1px solid var(--color-neutral-200);
  }
}