* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: #0f172a;
  color: #e2e8f0;
  display: grid;
  place-items: center;
  min-height: 100vh;
}
main {
  width: min(900px, 92vw);
  padding: 2rem;
}
h1 { margin: 0 0 1rem; font-size: 2rem; }
.card {
  background: #111827;
  border: 1px solid #1f2937;
  border-radius: 16px;
  padding: 1rem 1.25rem;
  margin: 1rem 0 2rem;
  box-shadow: 0 10px 25px rgba(0,0,0,0.25);
}
footer { opacity: 0.8; font-size: 0.9rem; }