:root {
  --bg:#ffffff; --fg:#0f172a; --muted:#64748b;
  --primary:#1e3a8a; --border:#e5e7eb;
  --ok:#166534; --err:#991b1b;
}

* { box-sizing: border-box; }
html,body { margin:0; padding:0; background:var(--bg); color:var(--fg);
  font:16px/1.5 system-ui,-apple-system,Segoe UI,Roboto,Arial,sans-serif; }
.container { max-width: 920px; margin: 0 auto; padding: 24px; }

.header { display:flex; align-items:center; justify-content:space-between;
  padding:16px 0; border-bottom:1px solid var(--border); }
.brand { font-weight:700; letter-spacing:.3px; }
.nav a { margin-left:16px; color:var(--primary); text-decoration:none; }

.hero { padding: 48px 0; }
h1 { margin:0 0 8px 0; }
h2 { margin:24px 0 8px; }

.card { border:1px solid var(--border); border-radius:8px; padding:16px; }
label { display:block; font-weight:600; margin:.5rem 0 .25rem; }

button { background:var(--primary); color:#fff; border:0; padding:.65rem 1rem;
  border-radius:6px; cursor:pointer; }
button:disabled { opacity:.6; cursor:not-allowed; }

.help { color:var(--muted); font-size:.95rem; }
footer { margin-top:48px; padding:16px 0; border-top:1px solid var(--border);
  color:var(--muted); font-size:.9rem; }