.topbar {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  padding: 0 clamp(16px, 4vw, 40px);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(12px);
  transition: box-shadow var(--transition-base);
}

.topbar.scrolled {
  box-shadow: var(--shadow-md);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 17px;
  font-weight: 700;
  color: var(--ink);
  letter-spacing: 0;
}

.brand-icon {
  width: 30px;
  height: 30px;
  border-radius: 50%;
  object-fit: cover;
}

.nav-links {
  display: flex;
  gap: 4px;
  align-items: center;
}

.nav-links a {
  display: inline-flex;
  align-items: center;
  height: 36px;
  padding: 0 14px;
  border-radius: var(--radius-full);
  font-size: 14px;
  font-weight: 500;
  color: var(--ink-secondary);
  transition: all var(--transition-fast);
}

.nav-links a:hover {
  color: var(--ink);
  background: var(--accent-subtle);
}

.nav-links a.is-active {
  color: var(--accent);
  background: var(--accent-subtle);
  font-weight: 600;
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  background: transparent;
  color: var(--ink-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  margin-left: 8px;
}

.theme-toggle:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-subtle);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
}

.mobile-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border: none;
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--ink);
  cursor: pointer;
}

.mobile-toggle svg {
  width: 24px;
  height: 24px;
}

.section-wrap {
  width: min(var(--container), calc(100% - 48px));
  margin: 0 auto;
}

.content-wrap {
  width: min(var(--content), calc(100% - 48px));
  margin: 0 auto;
}

@media (max-width: 768px) {
  .topbar {
    height: 56px;
  }

  .nav-links {
    display: none;
    position: fixed;
    inset: 56px 0 0;
    flex-direction: column;
    gap: 4px;
    padding: 16px;
    background: var(--surface);
    border-top: 1px solid var(--border);
    z-index: 99;
    animation: slideUp 0.2s ease;
  }

  .nav-links.is-open {
    display: flex;
  }

  .nav-links a {
    width: 100%;
    height: 48px;
    padding: 0 16px;
    font-size: 16px;
    border-radius: var(--radius-md);
  }

  .mobile-toggle {
    display: flex;
  }

  .theme-toggle {
    margin-left: 4px;
  }

  .section-wrap {
    width: min(var(--container), calc(100% - 32px));
  }
}