:root {
  --bg: #f3f5f8;
  --card: #fff;
  --text: #1d2433;
  --muted: #667085;
  --primary: #2459d6;
  --primary-hover: #1c47ad;
  --border: #d0d5dd;
  --error: #c62828;
  --error-bg: #fdecea;
  --ok: #1b873f;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #11151c;
    --card: #1a202b;
    --text: #e6e9ef;
    --muted: #98a2b3;
    --primary: #5b8cff;
    --primary-hover: #7aa2ff;
    --border: #344054;
    --error: #ff7b72;
    --error-bg: #3a1d1d;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 24px 16px;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
.card {
  width: 100%;
  max-width: 440px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 28px 24px;
}
h1 { font-size: 1.35rem; margin: 0; }
h2 { font-size: 1.2rem; margin: 8px 0; }
.sub, .muted { color: var(--muted); margin: 4px 0 0; font-size: .9rem; }
.steps {
  display: flex;
  gap: 4px;
  list-style: none;
  padding: 0;
  margin: 20px 0;
  font-size: .78rem;
  color: var(--muted);
}
.steps li { flex: 1; text-align: center; padding-top: 6px; border-top: 3px solid var(--border); }
.steps li.active, .steps li.past { color: var(--text); border-color: var(--primary); }
.step { display: flex; flex-direction: column; gap: 14px; }
.step[hidden] { display: none; }
label { display: flex; flex-direction: column; gap: 4px; font-weight: 600; font-size: .9rem; }
input {
  font: inherit;
  font-weight: 400;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: transparent;
  color: var(--text);
}
input:focus { outline: 2px solid var(--primary); outline-offset: 1px; }
input[aria-invalid="true"] { border-color: var(--error); }
.code { font-size: 1.5rem; letter-spacing: .4em; text-align: center; font-variant-numeric: tabular-nums; }
.err { color: var(--error); font-weight: 400; min-height: 1em; }
button {
  font: inherit;
  font-weight: 600;
  padding: 11px;
  border: 0;
  border-radius: 8px;
  background: var(--primary);
  color: #fff;
  cursor: pointer;
}
button:hover { background: var(--primary-hover); }
button:disabled { opacity: .6; cursor: wait; }
button.link { background: none; color: var(--primary); padding: 4px; font-weight: 400; }
.alert { background: var(--error-bg); color: var(--error); padding: 10px 12px; border-radius: 8px; margin-bottom: 14px; }
.howto { margin: 0; padding-left: 20px; font-size: .92rem; }
#qr { align-self: center; background: #fff; border-radius: 8px; padding: 6px; }
.secret { display: block; word-break: break-all; padding: 8px; border: 1px dashed var(--border); border-radius: 6px; user-select: all; }
details summary { cursor: pointer; color: var(--primary); font-size: .9rem; }
.done { align-items: center; text-align: center; }
.check {
  width: 56px; height: 56px; border-radius: 50%;
  display: grid; place-items: center;
  background: var(--ok); color: #fff; font-size: 2rem;
}