:root {
  --brand: #1d4ed8;
  --brand-dark: #1e3a8a;
  --brand-soft: #eff6ff;
  --ink: #1f2937;
  --muted: #6b7280;
  --line: #e5e7eb;
  --ok: #16a34a;
  --bg: #f4f6fb;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
.wrap { max-width: 880px; margin: 0 auto; padding: 24px 16px 64px; }
header.top {
  background: linear-gradient(135deg, var(--brand), var(--brand-dark));
  color: #fff; padding: 22px 20px; border-radius: 14px; margin-bottom: 22px;
  box-shadow: 0 8px 24px rgba(29, 78, 216, 0.25);
}
header.top h1 { margin: 0; font-size: 20px; letter-spacing: 0.5px; }
header.top p { margin: 6px 0 0; opacity: 0.9; font-size: 13px; }
.card {
  background: #fff; border: 1px solid var(--line); border-radius: 14px;
  padding: 22px; margin-bottom: 20px; box-shadow: 0 2px 10px rgba(15, 23, 42, 0.04);
}
.card h2 { margin: 0 0 16px; font-size: 16px; display: flex; align-items: center; gap: 8px; }
.card h2 .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--brand); }
label.field { display: block; margin-bottom: 14px; }
label.field > span { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
label.field .req { color: #dc2626; margin-left: 2px; }
input, textarea, select {
  width: 100%; padding: 10px 12px; border: 1px solid var(--line); border-radius: 9px;
  font-size: 14px; font-family: inherit; background: #fff; color: var(--ink);
}
input:focus, textarea:focus { outline: none; border-color: var(--brand); box-shadow: 0 0 0 3px var(--brand-soft); }
textarea { min-height: 64px; resize: vertical; }
.row2 { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
@media (max-width: 560px) { .row2 { grid-template-columns: 1fr; } }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  padding: 10px 18px; border: none; border-radius: 9px; background: var(--brand); color: #fff;
  font-size: 14px; font-weight: 600; cursor: pointer; transition: 0.15s;
}
.btn:hover { background: var(--brand-dark); }
.btn.ghost { background: #fff; color: var(--brand); border: 1px solid var(--brand); }
.btn.green { background: var(--ok); }
.btn:disabled { opacity: 0.55; cursor: not-allowed; }
.hidden { display: none !important; }
.qr-box { display: flex; flex-direction: column; align-items: center; gap: 12px; padding: 8px 0 4px; }
#qrcode { padding: 10px; background: #fff; border: 1px solid var(--line); border-radius: 10px; }
#qrcode img, #qrcode canvas { display: block; }
.url-line { display: flex; gap: 8px; align-items: center; width: 100%; }
.url-line input { background: var(--brand-soft); font-size: 13px; }
table.sheet { width: 100%; border-collapse: collapse; font-size: 14px; }
table.sheet th, table.sheet td { border: 1px solid var(--line); padding: 9px 10px; text-align: left; }
table.sheet th { background: var(--brand-soft); color: var(--brand-dark); font-weight: 600; }
table.sheet tr:nth-child(even) td { background: #fafbff; }
.banner {
  background: var(--brand-soft); border: 1px solid #bfdbfe; color: var(--brand-dark);
  border-radius: 10px; padding: 12px 14px; font-size: 14px; margin-bottom: 16px;
}
.banner b { color: var(--brand); }
.toolbar { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 18px; }
.tip { font-size: 12px; color: var(--muted); margin-top: 4px; }
.center { text-align: center; }
.success-big { font-size: 22px; color: var(--ok); font-weight: 700; margin: 10px 0; }
.kpi { font-size: 13px; color: var(--muted); }
.kpi b { color: var(--brand); font-size: 16px; }

/* ---------- 打印（报表页） ---------- */
.signin-sheet { background: #fff; border: 1px solid #cbd5e1; border-radius: 10px; padding: 22px 26px; }
.signin-sheet .st-title { text-align: center; font-size: 22px; font-weight: 800; margin: 0 0 18px; letter-spacing: 1px; }
.signin-sheet .st-meta { width: 100%; border-collapse: collapse; margin-bottom: 16px; }
.signin-sheet .st-meta td { border: 1px solid #94a3b8; padding: 7px 10px; font-size: 14px; vertical-align: top; }
.signin-sheet .st-meta td.lbl { background: #f1f5f9; font-weight: 600; width: 110px; white-space: nowrap; }
.signin-sheet table.stu { width: 100%; border-collapse: collapse; }
.signin-sheet table.stu th, .signin-sheet table.stu td { border: 1px solid #94a3b8; padding: 9px 10px; font-size: 14px; }
.signin-sheet table.stu th { background: #e2e8f0; }
.signin-sheet table.stu td.idx { text-align: center; width: 56px; }
.signin-sheet .st-foot { margin-top: 26px; display: flex; justify-content: space-between; font-size: 13px; color: #475569; }
@media print {
  body { background: #fff; }
  .wrap { max-width: none; padding: 0; }
  header.top, .toolbar, .banner, .tip, #app-msg, .gate { display: none !important; }
  .card { border: none; box-shadow: none; padding: 0; }
  .signin-sheet { border: none; padding: 0; }
}

/* ---------- 讲师台访问口令 gate ---------- */
.gate { position: fixed; inset: 0; background: rgba(15, 23, 42, 0.55); display: flex; align-items: center; justify-content: center; z-index: 1000; }
.gate-box { background: #fff; border-radius: 14px; padding: 26px 24px; width: 320px; max-width: 90vw; box-shadow: 0 20px 50px rgba(0, 0, 0, 0.3); text-align: center; }
.gate-box h2 { margin: 0 0 8px; font-size: 17px; }
.gate-tip { font-size: 12px; color: var(--muted); margin: 0 0 14px; }
.gate-box input { margin-bottom: 12px; text-align: center; letter-spacing: 2px; }
.gate-err { color: #dc2626; font-size: 13px; min-height: 18px; margin-top: 8px; }

/* ---------- 双栏签到表（报表页） ---------- */
.signin-sheet table.stu-dual { width: 100%; border-collapse: collapse; }
.signin-sheet table.stu-dual th, .signin-sheet table.stu-dual td { border: 1px solid #94a3b8; padding: 9px 10px; font-size: 14px; }
.signin-sheet table.stu-dual th { background: #e2e8f0; }
.signin-sheet table.stu-dual td.idx { text-align: center; width: 52px; }
/* 双栏之间的分隔线（左栏 D 列之后） */
.signin-sheet table.stu-dual th:nth-child(5), .signin-sheet table.stu-dual td:nth-child(5) { border-left: 2px solid #64748b; }

/* ---------- 名单行内操作（讲师端） ---------- */
table.sheet td.ops { white-space: nowrap; width: 86px; text-align: center; }
.mini { padding: 3px 9px; font-size: 12px; border-radius: 6px; border: 1px solid var(--line); background: #fff; cursor: pointer; margin: 0 3px; }
.mini:hover { background: var(--brand-soft); }
.mini.danger { color: #dc2626; border-color: #fecaca; }
.mini.danger:hover { background: #fee2e2; }