:root { color-scheme: dark; }
* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: system-ui, sans-serif;
  background: #0f1419;
  color: #e6edf3;
}
.card {
  padding: 1.75rem 2rem;
  border-radius: 12px;
  background: #161b22;
  box-shadow: 0 8px 32px rgba(0,0,0,.4);
  max-width: 22rem;
}
button {
  margin-top: 0.5rem;
  padding: 0.5rem 1rem;
  border-radius: 8px;
  border: 0;
  cursor: pointer;
  font-size: 1rem;
  background: #238636;
  color: #fff;
}
button:hover { filter: brightness(1.08); }