:root {
  --bg: #f6f7fb;
  --panel: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --border: #e5e7eb;
  --accent: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
}
* { box-sizing: border-box; }
html, body {
  margin: 0; padding: 0; background: var(--bg); color: var(--text);
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  font-size: 14px; line-height: 1.55;
}
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
.wrap { max-width: 960px; margin: 0 auto; padding: 0 12px; }
.hide { display: none !important; }

/* ---------- Header ---------- */
.site-header {
  background: linear-gradient(135deg, #2563eb, #7c3aed); color: #fff;
  padding: 16px 0 14px;
}
.site-header h1 { margin: 0 0 2px; font-size: 18px; font-weight: 600; }
.site-header .subtitle { margin: 0; opacity: .9; font-size: 12px; }
.site-header.compact { padding: 10px 0; }
.site-header.compact h1 { font-size: 16px; margin: 0; }
.header-row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.header-row .spacer { flex: 1; }
.back-link { color: #fff; opacity: .9; font-size: 13px; white-space: nowrap; }
.back-link:hover { opacity: 1; text-decoration: none; }

.user-badge { display: flex; align-items: center; gap: 6px; }
.user-badge .ub-name { color: #fff; font-size: 12px; opacity: .95; max-width: 180px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.user-badge .ub-logout { color: #fff; opacity: .85; font-size: 12px; cursor: pointer; background: none; border: 1px solid rgba(255,255,255,.35); padding: 2px 8px; border-radius: 4px; }
.user-badge .ub-logout:hover { background: rgba(255,255,255,.15); opacity: 1; }

/* ---------- Mode cards (home) ---------- */
.mode-cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 14px 0; }
.mode-card {
  display: flex; align-items: center; gap: 10px; background: var(--panel);
  border: 1px solid var(--border); border-radius: 10px; padding: 12px 14px;
  transition: transform .12s, box-shadow .12s; color: var(--text);
}
.mode-card:hover { transform: translateY(-1px); box-shadow: 0 4px 12px rgba(0,0,0,.08); text-decoration: none; }
.mode-card.primary { background: linear-gradient(135deg, #2563eb, #4f46e5); color: #fff; border: none; }
.mode-card.primary p { color: rgba(255,255,255,.85); }
.mode-card.secondary { background: linear-gradient(135deg, #059669, #0d9488); color: #fff; border: none; }
.mode-card.secondary p { color: rgba(255,255,255,.85); }
.mode-icon { font-size: 22px; flex: 0 0 auto; }
.mode-card h2 { margin: 0; font-size: 14px; font-weight: 600; line-height: 1.2; }
.mode-card p { margin: 2px 0 0; font-size: 11px; color: var(--muted); }

/* ---------- Stats & sections ---------- */
.stats h2, .category-list h2, .paper-list h2 {
  font-size: 14px; margin: 16px 0 6px; font-weight: 600;
}
.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px; }
.stat-card { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 10px 6px; text-align: center; }
.stat-num { font-size: 18px; font-weight: 700; color: var(--primary); }
.stat-label { color: var(--muted); font-size: 11px; margin-top: 2px; }

.hint { color: var(--muted); font-size: 12px; margin: 0 0 8px; }

.cat-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 8px; }
.cat-card {
  background: var(--panel); border: 1px solid var(--border);
  border-left: 3px solid var(--cat-color, var(--primary));
  border-radius: 8px; padding: 10px 12px; color: var(--text);
  transition: transform .1s;
}
.cat-card:hover { transform: translateY(-1px); box-shadow: 0 3px 8px rgba(0,0,0,.06); text-decoration: none; }
.cat-icon { font-size: 18px; }
.cat-name { font-weight: 600; font-size: 13px; margin-top: 2px; }
.cat-count { color: var(--muted); font-size: 11px; }

.paper-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(100px, 1fr)); gap: 6px; }
.paper-card { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 8px 6px; text-align: center; color: var(--text); transition: border-color .1s; }
.paper-card:hover { border-color: var(--primary); text-decoration: none; }
.paper-year { font-size: 16px; font-weight: 700; }
.paper-src { font-size: 10px; color: var(--muted); margin: 1px 0 2px; }
.paper-count { font-size: 11px; color: var(--primary); }

.site-footer { margin-top: 20px; padding: 14px 0; color: var(--muted); font-size: 11px; text-align: center; border-top: 1px solid var(--border); }

/* ---------- Toolbar / filters (practice page) ---------- */
.toolbar {
  background: var(--panel); padding: 10px 12px; margin: 10px auto 0;
  max-width: 960px; border: 1px solid var(--border); border-radius: 10px;
  display: flex; flex-wrap: wrap; gap: 8px; align-items: center; justify-content: space-between;
}
.filters { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; flex: 1; }
.filters label { font-size: 12px; color: var(--muted); display: flex; align-items: center; gap: 4px; }
.filters select { padding: 4px 8px; font-size: 13px; border: 1px solid var(--border); border-radius: 5px; background: #fff; }
.status { color: var(--muted); font-size: 12px; }
.status .sep { margin: 0 4px; }

/* ---------- Question shell ---------- */
.practice-main { margin-top: 10px; padding-bottom: 60px; }
.q-shell { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 14px 16px; margin-bottom: 10px; }
.q-header { display: flex; align-items: center; gap: 8px; margin-bottom: 10px; flex-wrap: wrap; }
.q-badge { background: var(--primary); color: #fff; padding: 3px 10px; border-radius: 14px; font-weight: 600; font-size: 12px; }
.q-meta { display: flex; gap: 4px; flex: 1; flex-wrap: wrap; }
.meta-chip { background: #eef2ff; color: #4338ca; padding: 2px 8px; border-radius: 12px; font-size: 11px; }
.meta-chip.cat-chip { background: #ecfdf5; color: #065f46; }
.flag-btn { background: none; border: none; font-size: 18px; color: var(--muted); cursor: pointer; padding: 2px 6px; }
.flag-btn.flagged { color: var(--warning); }

.q-stem { font-size: 14px; line-height: 1.75; white-space: pre-wrap; word-wrap: break-word; margin-bottom: 12px; }
.q-options { display: flex; flex-direction: column; gap: 6px; }
.opt {
  display: flex; gap: 8px; padding: 8px 12px; border: 1.5px solid var(--border);
  border-radius: 8px; cursor: pointer; transition: all .1s; background: #fff; font-size: 13px;
}
.opt:hover { border-color: var(--primary); background: #f8fafc; }
.opt.chosen { border-color: var(--primary); background: #eff6ff; }
.opt-letter { font-weight: 700; color: var(--primary); flex: 0 0 20px; }
.opt-text { flex: 1; white-space: pre-wrap; word-wrap: break-word; }

.q-answer-area { margin-top: 12px; padding-top: 10px; border-top: 1px dashed var(--border); }
.user-choice { font-size: 13px; }
.user-choice strong { color: var(--primary); }

/* Correctness */
.opt.correct { border-color: #10b981; background: #ecfdf5; }
.opt.correct .opt-letter { color: #065f46; }
.opt.wrong { border-color: #ef4444; background: #fef2f2; }
.opt.wrong .opt-letter { color: #991b1b; }
.correct-mark { color: #059669; font-weight: 600; }
.wrong-mark { color: #dc2626; font-weight: 600; }

/* Nav */
.nav-row { display: flex; align-items: center; justify-content: space-between; gap: 6px; margin: 10px 0; }
.btn {
  background: #fff; border: 1px solid var(--border); padding: 6px 12px;
  border-radius: 6px; cursor: pointer; font-size: 13px; color: var(--text); transition: all .1s;
}
.btn:hover { border-color: var(--primary); color: var(--primary); }
.btn.primary { background: var(--primary); color: #fff; border-color: var(--primary); }
.btn.primary:hover { background: var(--primary-dark); color: #fff; }
.btn.danger { background: var(--danger); color: #fff; border-color: var(--danger); }
.btn.danger:hover { background: #b91c1c; color: #fff; }
.btn.small { padding: 4px 8px; font-size: 12px; }
.btn.big { padding: 10px 20px; font-size: 14px; }
.btn:disabled { opacity: .5; cursor: not-allowed; }

.jump { font-size: 12px; color: var(--muted); }
.jump input { width: 50px; padding: 4px 6px; border: 1px solid var(--border); border-radius: 5px; font-size: 12px; text-align: center; }

/* Grid navigator */
.grid-nav {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(28px, 1fr));
  gap: 4px; padding: 10px; background: var(--panel); border: 1px solid var(--border);
  border-radius: 10px; margin-bottom: 10px;
}
.grid-nav .gn {
  aspect-ratio: 1; display: flex; align-items: center; justify-content: center;
  border-radius: 4px; background: #f3f4f6; color: var(--text); font-size: 11px;
  cursor: pointer; border: 1px solid transparent; transition: all .08s; position: relative;
}
.grid-nav .gn:hover { border-color: var(--primary); }
.grid-nav .gn.current { background: var(--primary); color: #fff; }
.grid-nav .gn.answered { background: #dbeafe; color: #1e40af; }
.grid-nav .gn.correct-sm { background: #a7f3d0; color: #065f46; }
.grid-nav .gn.wrong-sm { background: #fecaca; color: #991b1b; }
.grid-nav .gn.flagged::after { content: '★'; font-size: 8px; position: absolute; top: 1px; right: 2px; color: var(--warning); }

/* Start card */
.start-card { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 20px; margin-top: 14px; }
.start-card h2 { margin: 0 0 8px; font-size: 15px; }
.exam-intro { color: var(--muted); padding-left: 18px; font-size: 12px; }
.exam-intro li { margin: 3px 0; }
.exam-options { margin: 10px 0; display: flex; flex-direction: column; gap: 4px; }
.exam-options label { color: var(--muted); font-size: 13px; cursor: pointer; }
.exam-buttons { display: flex; gap: 8px; margin-top: 12px; }

.timer { background: rgba(255,255,255,.18); padding: 4px 10px; border-radius: 14px; font-family: "SF Mono", monospace; font-weight: 600; font-size: 12px; color: #fff; }
.exam-progress { color: var(--muted); font-size: 12px; }
.submit-row { text-align: center; margin-top: 10px; }

/* Result */
.result-card { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 20px; margin-top: 14px; }
.result-card h2 { margin: 0 0 10px; font-size: 16px; }
.result-stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px; margin: 12px 0; }
.result-stats > div { text-align: center; background: #f9fafb; padding: 10px 4px; border-radius: 8px; }
.result-stats strong { display: block; font-size: 18px; color: var(--primary); }
.result-stats span { color: var(--muted); font-size: 11px; }
.result-breakdown h3 { font-size: 13px; margin: 12px 0 6px; }
.result-breakdown .rb-row { display: flex; justify-content: space-between; padding: 4px 0; border-bottom: 1px solid var(--border); font-size: 12px; }
.result-actions { display: flex; gap: 6px; margin-top: 12px; flex-wrap: wrap; }

/* ---------- Auth pages ---------- */
body.auth-bg { background: linear-gradient(135deg, #2563eb, #7c3aed); min-height: 100vh; display: flex; align-items: center; justify-content: center; font-size: 14px; }
.auth-wrap { width: 100%; max-width: 360px; padding: 16px; }
.auth-card { background: #fff; border-radius: 12px; padding: 24px 22px; box-shadow: 0 12px 40px rgba(0,0,0,.22); }
.auth-title { margin: 0 0 4px; font-size: 17px; line-height: 1.35; text-align: center; color: #1f2937; }
.auth-sub { margin: 0 0 16px; text-align: center; color: #6b7280; font-size: 12px; }
.auth-form { display: flex; flex-direction: column; gap: 10px; }
.auth-form label { display: flex; flex-direction: column; gap: 4px; font-size: 12px; color: #374151; font-weight: 500; }
.auth-form input { padding: 8px 10px; border: 1px solid #e5e7eb; border-radius: 6px; font-size: 14px; }
.auth-form input:focus { outline: none; border-color: #2563eb; }
.auth-form .btn.primary.big { margin-top: 4px; }
.auth-msg { text-align: center; margin: 2px 0 0; font-size: 12px; min-height: 14px; }
.auth-msg.err { color: #dc2626; }
.auth-msg.ok  { color: #059669; }
.auth-foot { text-align: center; margin: 14px 0 0; font-size: 12px; color: #6b7280; }

/* ---------- Coverage bar ---------- */
.coverage-bar { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 10px 14px; margin: 0 0 12px; }
.cov-text { font-size: 12px; color: var(--muted); margin-bottom: 6px; }
.cov-text strong { color: var(--primary); font-size: 14px; }
.cov-track { background: #e5e7eb; border-radius: 999px; height: 6px; overflow: hidden; }
.cov-fill { background: linear-gradient(90deg, #10b981, #3b82f6); height: 100%; transition: width .3s; }
.cov-hint { margin: 6px 0 0; font-size: 11px; color: #6b7280; }

/* Announcements banner */
.ann-banner { padding: 8px 12px; border-radius: 8px; margin-bottom: 8px; font-size: 12px; border-left: 3px solid; }
.ann-banner.level-info { background: #dbeafe; color: #1e3a8a; border-color: #2563eb; }
.ann-banner.level-warning { background: #fef3c7; color: #78350f; border-color: #f59e0b; }
.ann-banner.level-danger { background: #fee2e2; color: #7f1d1d; border-color: #ef4444; }
.ann-banner strong { font-size: 13px; }

/* Exam grade */
.grade-area { background: #f9fafb; border-radius: 10px; padding: 16px; margin-bottom: 12px; }
.grade-big { text-align: center; margin-bottom: 6px; }
.grade-score { font-size: 32px; font-weight: 700; color: var(--primary); }
.grade-score span { font-size: 16px; color: var(--muted); font-weight: 400; }
.grade-label { color: var(--muted); font-size: 12px; }
.grade-note { text-align: center; color: var(--muted); font-size: 11px; margin: 6px 0 0; }

/* ---------- Suggest modal ---------- */
.suggest-area { margin-top: 8px; padding: 8px 10px; background: #fef3c7; border-left: 3px solid #f59e0b; border-radius: 5px; font-size: 12px; color: #78350f; display: flex; gap: 6px; align-items: center; flex-wrap: wrap; }
.suggest-modal { position: fixed; inset: 0; background: rgba(0,0,0,.55); display: flex; align-items: center; justify-content: center; z-index: 1000; padding: 12px; }
.suggest-modal-inner { background: #fff; border-radius: 10px; padding: 20px; max-width: 440px; width: 100%; }
.suggest-modal-inner h3 { margin: 0 0 8px; font-size: 15px; }
.suggest-modal-inner select, .suggest-modal-inner textarea, .suggest-modal-inner input {
  width: 100%; padding: 7px 10px; border: 1px solid #e5e7eb; border-radius: 6px;
  font-size: 13px; margin-bottom: 10px; font-family: inherit; box-sizing: border-box;
}
.suggest-modal-inner textarea { resize: vertical; min-height: 60px; }
.suggest-modal-inner .sm-buttons { display: flex; gap: 6px; justify-content: flex-end; }
.suggest-modal-inner label { display: block; font-size: 12px; color: #374151; margin-bottom: 4px; font-weight: 500; }

/* ---------- Floating submit FAB ---------- */
.fab {
  position: fixed; right: 14px; bottom: 14px; z-index: 900;
  background: linear-gradient(135deg, #f59e0b, #ef4444); color: #fff;
  border: none; width: 48px; height: 48px; border-radius: 50%;
  font-size: 22px; cursor: pointer; box-shadow: 0 4px 14px rgba(239,68,68,.4);
  display: flex; align-items: center; justify-content: center;
}
.fab:hover { transform: scale(1.06); }

/* ---------- Admin panel ---------- */
.admin-main { padding-bottom: 30px; }
.admin-card { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 16px; margin: 10px 0; }
.admin-card h2 { margin: 0 0 8px; font-size: 15px; }
.admin-controls { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; margin: 8px 0; }
.admin-controls select, .admin-controls input[type=text], .admin-controls input[type=password] {
  padding: 5px 8px; font-size: 13px; border: 1px solid var(--border); border-radius: 5px; background: #fff;
}
.admin-card textarea { width: 100%; font-family: "SF Mono", monospace; font-size: 12px; padding: 8px; border: 1px solid var(--border); border-radius: 6px; resize: vertical; }
.chip { background: #eef2ff; color: #4338ca; padding: 2px 8px; border-radius: 12px; font-size: 11px; }
.chip.ok  { background: #d1fae5; color: #065f46; }
.chip.err { background: #fee2e2; color: #991b1b; }
.preview { background: #f9fafb; border-radius: 6px; padding: 10px; margin-top: 8px; font-size: 12px; }
.pv-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(50px, 1fr)); gap: 3px; margin-top: 6px; }
.pv-cell { text-align: center; padding: 3px 5px; border-radius: 3px; font-size: 11px; font-family: "SF Mono", monospace; }
.pv-hit { background: #d1fae5; color: #065f46; }
.pv-miss { background: #fee2e2; color: #991b1b; }
.pv-orphan { background: #fed7aa; color: #92400e; }

.cov-big { font-size: 14px; margin-bottom: 6px; }
.cov-big strong { color: var(--primary); }
.cov-paper-list { margin-top: 10px; display: flex; flex-direction: column; gap: 4px; }
.cov-row { display: grid; grid-template-columns: 1fr 2fr auto; gap: 8px; align-items: center; font-size: 12px; }
.cov-track-sm { background: #e5e7eb; border-radius: 999px; height: 5px; overflow: hidden; }
.cov-fill-sm { display: block; background: linear-gradient(90deg, #10b981, #3b82f6); height: 100%; }
.cov-num { font-family: "SF Mono", monospace; color: var(--muted); font-size: 11px; }

.manual-list { display: flex; flex-direction: column; gap: 8px; max-height: 640px; overflow-y: auto; }
.manual-row { background: #f9fafb; border: 1px solid var(--border); border-radius: 8px; padding: 10px; }
.mr-head { display: flex; gap: 6px; align-items: center; margin-bottom: 4px; flex-wrap: wrap; }
.mr-stem { font-size: 12px; line-height: 1.55; margin-bottom: 6px; }
.mr-opts { display: grid; grid-template-columns: 1fr 1fr; gap: 2px 10px; font-size: 11px; color: #374151; margin-bottom: 6px; }
.mr-opt { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.mr-actions { display: flex; gap: 4px; flex-wrap: wrap; align-items: center; }

/* Admin nav tabs */
.admin-nav { display: flex; gap: 3px; flex-wrap: wrap; }
.admin-nav .tab-btn {
  background: rgba(255,255,255,.14); color: #fff; border: none;
  padding: 5px 10px; border-radius: 5px; font-size: 12px; cursor: pointer;
}
.admin-nav .tab-btn:hover { background: rgba(255,255,255,.24); }
.admin-nav .tab-btn.active { background: #fff; color: #2563eb; font-weight: 600; }
.tab-pane { margin-top: 12px; }

/* Table */
table.admin-table { width: 100%; border-collapse: collapse; font-size: 12px; }
table.admin-table th { background: #f3f4f6; padding: 6px 8px; text-align: left; font-weight: 600; }
table.admin-table td { padding: 6px 8px; border-bottom: 1px solid var(--border); }

/* ---------- Responsive ---------- */
@media (max-width: 640px) {
  body { font-size: 13px; }
  .wrap { padding: 0 10px; }
  .site-header { padding: 12px 0 10px; }
  .site-header h1 { font-size: 16px; }
  .site-header.compact h1 { font-size: 14px; }
  .site-header .subtitle { font-size: 11px; }
  .mode-cards { grid-template-columns: 1fr; gap: 6px; }
  .mode-card { padding: 10px 12px; }
  .mode-icon { font-size: 20px; }
  .mode-card h2 { font-size: 13px; }
  .stats-grid { grid-template-columns: repeat(4, 1fr); gap: 4px; }
  .stat-card { padding: 7px 4px; }
  .stat-num { font-size: 15px; }
  .stat-label { font-size: 10px; }
  .cat-grid { grid-template-columns: repeat(2, 1fr); gap: 6px; }
  .cat-card { padding: 8px 10px; }
  .cat-icon { font-size: 16px; }
  .cat-name { font-size: 12px; }
  .paper-grid { grid-template-columns: repeat(4, 1fr); gap: 4px; }
  .paper-card { padding: 6px 4px; }
  .paper-year { font-size: 13px; }
  .paper-src, .paper-count { font-size: 9px; }
  .result-stats { grid-template-columns: repeat(2, 1fr); }
  .mr-opts { grid-template-columns: 1fr; }
  .cov-row { grid-template-columns: 1fr; gap: 3px; }
  .filters { width: 100%; }
  .filters select { flex: 1; min-width: 0; font-size: 12px; padding: 5px 6px; }
  .toolbar { padding: 8px 10px; }
  .status { width: 100%; font-size: 11px; }
  .q-shell { padding: 12px 12px; }
  .q-stem { font-size: 13px; }
  .opt { padding: 7px 10px; font-size: 12px; }
  .grid-nav { grid-template-columns: repeat(auto-fill, minmax(24px, 1fr)); gap: 3px; padding: 6px; }
  .grid-nav .gn { font-size: 10px; }
  .nav-row { flex-wrap: wrap; }
  .fab { width: 44px; height: 44px; font-size: 20px; }
  .admin-nav .tab-btn { padding: 4px 8px; font-size: 11px; }
  .header-row { gap: 6px; }
  .user-badge .ub-name { max-width: 110px; font-size: 11px; }
  .user-badge .ub-logout { font-size: 11px; padding: 1px 6px; }
  table.admin-table th, table.admin-table td { padding: 4px 6px; font-size: 11px; }
}