:root { --bg: #fafaf8; --fg: #1d1d1b; --muted: #6b6b66; --line: #e2e2dc; --accent: #C8102E; --card: #ffffff; }
@media (prefers-color-scheme: dark) {
  :root { --bg: #161615; --fg: #ededea; --muted: #9a9a94; --line: #2c2c2a; --accent: #ff5a6e; --card: #1e1e1c; }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--fg);
       font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; }
header { position: sticky; top: 0; background: var(--bg); border-bottom: 1px solid var(--line); padding: 12px 16px 0; }
h1 { font-size: 1.125rem; margin: 0 0 8px; }
nav { display: flex; gap: 4px; overflow-x: auto; }
nav button { font: inherit; background: none; border: 0; border-bottom: 2px solid transparent; color: var(--muted);
             padding: 8px 12px; cursor: pointer; white-space: nowrap; }
nav button[aria-current="page"] { color: var(--fg); border-bottom-color: var(--accent); }
main { max-width: 64rem; margin: 0 auto; padding: 16px; }
.muted { color: var(--muted); }
.error { color: var(--accent); }