.site-header {
  position: sticky; top: 0; z-index: 10;
  background: var(--surface); border-bottom: 1px solid var(--border);
}
.nav { display: flex; align-items: center; justify-content: space-between; height: 60px; position: relative; }
.brand { font-weight: 700; font-size: 1.15rem; text-decoration: none; color: var(--text); }
.nav-links { display: flex; gap: 1.25rem; }
.nav-links a { text-decoration: none; color: var(--text); }
.nav-links a:hover { color: var(--accent); }

.nav-toggle { display: none; }
.nav-burger { display: none; cursor: pointer; padding: .5rem; }
.nav-burger span, .nav-burger span::before {
  display: block; width: 22px; height: 2px; background: var(--text); position: relative;
}
.nav-burger span::before { content: ""; position: absolute; top: -7px; }

@media (max-width: 768px) {
  .nav-burger { display: block; }
  .nav-links {
    display: none; position: absolute; top: 60px; left: 0; right: 0;
    flex-direction: column; gap: 0; background: var(--surface);
    border-bottom: 1px solid var(--border);
  }
  .nav-links a { padding: .9rem var(--space); border-top: 1px solid var(--border); }
  .nav-toggle:checked ~ .nav-links { display: flex; }
}

.site-footer { background: #111827; color: #d1d5db; padding: 1.5rem 0; font-size: .9rem; }
.footer-inner { display: flex; flex-wrap: wrap; gap: .75rem; justify-content: space-between; }
.site-footer a { color: #d1d5db; margin-left: 1rem; }

.error-page { text-align: center; padding-top: 4rem; }
.error-code { font-size: 4rem; font-weight: 800; margin: 0; color: var(--accent); }
.error-detail { text-align: left; overflow-x: auto; padding: 1rem; background: var(--surface); border-radius: var(--radius); }