:root { color-scheme: dark; }
* { box-sizing: border-box; }
body {
  margin: 0; min-height: 100vh; display: grid; place-items: center;
  background: #0d1117; color: #c9d1d9;
  font: 14px/1.5 system-ui, -apple-system, Segoe UI, sans-serif;
}
.card {
  background: #161b22; border: 1px solid #21262d; border-radius: 10px;
  padding: 28px 32px; max-width: 420px; text-align: center;
}
h1 { margin: 0 0 6px; font-size: 20px; letter-spacing: 0.3px; }
.muted { color: #8b949e; }
.warn { color: #e3b341; }
.btn {
  display: inline-block; margin-top: 8px; padding: 6px 14px; border-radius: 6px;
  background: #21262d; border: 1px solid #30363d; color: #c9d1d9; text-decoration: none;
}
.btn:hover { border-color: #8b949e; }