:root {
  color-scheme: dark;
  --bg-primary: #0b101b;
  --bg-header: #0f172a;
  --bg-card: #131c2e;
  --bg-badge: #1e293b;
  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --accent-cyan: #38bdf8;
  --accent-amber: #fbbf24;
  --border-subtle: #263554;
}
:root[data-theme="light"] {
  color-scheme: light;
  --bg-primary: #f4f6f9;
  --bg-header: #ffffff;
  --bg-card: #ffffff;
  --bg-badge: #fff8e6;
  --text-primary: #111926;
  --text-secondary: #374559;
  --accent-cyan: #0b5cab;
  --accent-amber: #b26b00;
  --border-subtle: #cfd8e3;
}
* { box-sizing: border-box; }
html, body {
  margin: 0;
  padding: 0;
  max-width: 100%;
  overflow-x: hidden;
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  line-height: 1.6;
}
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--accent-cyan);
  color: #000;
  padding: 0.5rem 1rem;
  font-weight: 700;
  z-index: 1000;
}
.skip-link:focus {
  left: 0.5rem;
  top: 0.5rem;
}
a { color: var(--accent-cyan); text-decoration: underline; }
a:focus-visible, button:focus-visible {
  outline: 3px solid var(--accent-amber);
  outline-offset: 2px;
}
header.site-header {
  border-bottom: 1px solid var(--border-subtle);
  background: var(--bg-header);
  padding: 1rem 1.25rem;
}
.header-inner {
  max-width: 1080px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.brand-title {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--text-primary);
  text-decoration: none;
}
nav ul.nav-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.25rem;
}
.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 600;
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
}
.nav-link.active, .nav-link:hover {
  color: var(--text-primary);
  background: var(--bg-card);
}
main#main-content {
  max-width: 1080px;
  margin: 0 auto;
  padding: 2rem 1.25rem;
}
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}
.badge {
  display: inline-block;
  padding: 0.2rem 0.65rem;
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 700;
  background: var(--bg-badge);
  color: var(--accent-amber);
  border: 1px solid var(--accent-amber);
}
.theme-toggle-btn, .interactive-btn {
  background: var(--bg-card);
  color: var(--text-primary);
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  padding: 0.4rem 0.8rem;
  font-size: 0.88rem;
  font-weight: 600;
  cursor: pointer;
}
.theme-toggle-btn:hover, .interactive-btn:hover {
  border-color: var(--accent-cyan);
}
pre.interactive-output {
  background: var(--bg-primary);
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  padding: 0.85rem;
  overflow-x: auto;
  font-size: 0.85rem;
  white-space: pre-wrap;
}
.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.25rem;
}
footer.site-footer {
  border-top: 1px solid var(--border-subtle);
  padding: 1.5rem 1.25rem;
  margin-top: 3rem;
  color: var(--text-secondary);
  font-size: 0.9rem;
}
.footer-inner {
  max-width: 1080px;
  margin: 0 auto;
}