:root {
  color-scheme: dark;
  --page: #0d0d0d; --surface: #1a1a19; --text: #f0efec; --text-2: #c3c2b7; --muted: #898781;
  --border: rgba(255, 255, 255, 0.10); --accent: #3987e5; --critical: #e66767;
}
* { box-sizing: border-box; }
body {
  margin: 0; min-height: 100vh; display: grid; place-items: center; padding: 16px;
  background: radial-gradient(1200px 600px at 50% -10%, #16243a 0%, var(--page) 60%);
  color: var(--text); font: 16px/1.5 system-ui, -apple-system, "Segoe UI", sans-serif;
}
.card {
  width: 100%; max-width: 380px; background: var(--surface); border: 1px solid var(--border);
  border-radius: 16px; padding: 32px 24px; text-align: center;
}
h1 { margin: 12px 0 0; font-size: 22px; font-weight: 650; }
.sub { margin: 4px 0 20px; color: var(--muted); font-size: 14px; }
form { display: grid; gap: 8px; text-align: left; }
label { font-size: 14px; color: var(--text-2); margin-top: 8px; }
label span { color: var(--muted); font-size: 12px; }
input {
  width: 100%; padding: 12px 14px; border-radius: 10px; border: 1px solid var(--border);
  background: #121211; color: var(--text); font-size: 16px;
}
input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
#code { letter-spacing: 0.3em; font-variant-numeric: tabular-nums; }
button {
  margin-top: 16px; padding: 12px; border: 0; border-radius: 10px; background: var(--accent);
  color: #fff; font-size: 16px; font-weight: 600; cursor: pointer;
}
button:hover { filter: brightness(1.1); }
.error { color: var(--critical); background: rgba(230, 103, 103, 0.1); border-radius: 8px; padding: 8px; font-size: 14px; }
.foot { margin: 20px 0 0; color: var(--muted); font-size: 12px; }