:root {
  --bg: #0f1420;
  --panel: #161d2e;
  --panel-2: #1d2537;
  --border: #2a3349;
  --text: #e7ebf3;
  --text-dim: #9aa5bd;
  --accent: #4c8dff;
  --accent-2: #7c5cff;
  --good: #34c77b;
  --bad: #ef5a6f;
  --warn: #f5a623;
  --radius: 12px;
  font-size: 16px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "PingFang TC", "Noto Sans TC", "Microsoft JhengHei", Segoe UI, Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(15, 20, 32, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.topbar-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 14px 20px;
  display: flex;
  align-items: center;
  gap: 24px;
  flex-wrap: wrap;
}

.topbar h1 {
  font-size: 18px;
  margin: 0;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  white-space: nowrap;
}

.tabs { display: flex; gap: 8px; flex-wrap: wrap; }

.tab-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 8px 14px;
  border-radius: 999px;
  cursor: pointer;
  font-size: 14px;
  transition: all .15s ease;
}
.tab-btn:hover { border-color: var(--accent); color: var(--text); }
.tab-btn.active {
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  color: white;
  border-color: transparent;
}

#app { max-width: 1100px; margin: 0 auto; padding: 24px 20px 80px; }

.view { display: none; }
.view.active { display: block; }

/* Filters */
.filters {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 18px;
  align-items: center;
}

input, select {
  background: var(--panel);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 9px 12px;
  border-radius: 8px;
  font-size: 14px;
}
input:focus, select:focus { outline: none; border-color: var(--accent); }

#search-input { flex: 1; min-width: 220px; }

.count-badge {
  color: var(--text-dim);
  font-size: 13px;
  white-space: nowrap;
}

/* Question list & cards */
.question-list { display: flex; flex-direction: column; gap: 14px; }

.question-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
}

.q-meta {
  display: flex;
  gap: 8px;
  align-items: center;
  margin-bottom: 8px;
  flex-wrap: wrap;
}

.badge {
  font-size: 12px;
  padding: 3px 9px;
  border-radius: 999px;
  border: 1px solid var(--border);
  color: var(--text-dim);
}
.badge.cat { border-color: var(--accent); color: var(--accent); }
.badge.cs { border-color: var(--accent-2); color: var(--accent-2); }
.badge.cs.legacy { border-color: var(--text-dim); color: var(--text-dim); text-decoration: line-through; }
.badge.num { color: var(--text-dim); }
.badge.multi { border-color: var(--warn); color: var(--warn); }
.badge.legacy-tag { border-color: var(--bad); color: var(--bad); }
.badge.training-tag { border-color: var(--good); color: var(--good); }

.q-text-en {
  font-size: 15px;
  color: var(--text);
  white-space: pre-line;
  margin-bottom: 4px;
}
.q-text-zh {
  font-size: 15px;
  color: #cfe0ff;
  white-space: pre-line;
  margin-bottom: 12px;
  padding-top: 6px;
  border-top: 1px dashed var(--border);
}

.options { display: flex; flex-direction: column; gap: 8px; margin-bottom: 10px; }

.option {
  display: flex;
  gap: 10px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel-2);
  cursor: pointer;
  transition: all .12s ease;
}
.option:hover { border-color: var(--accent); }
.option .opt-letter {
  flex-shrink: 0;
  width: 22px; height: 22px;
  border-radius: 6px;
  border: 1px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  font-size: 12px;
  color: var(--text-dim);
}
.option .opt-text { flex: 1; font-size: 14px; }
.option .opt-text-zh { font-size: 13px; color: var(--text-dim); margin-top: 2px; }

.option.correct-reveal { border-color: var(--good); background: rgba(52,199,123,0.1); }
.option.correct-reveal .opt-letter { background: var(--good); color: white; border-color: var(--good); }
.option.wrong-selected { border-color: var(--bad); background: rgba(239,90,111,0.1); }
.option.wrong-selected .opt-letter { background: var(--bad); color: white; border-color: var(--bad); }
.option.selected:not(.correct-reveal):not(.wrong-selected) { border-color: var(--accent); }
.option.selected:not(.correct-reveal):not(.wrong-selected) .opt-letter { background: var(--accent); color: white; border-color: var(--accent); }
.option.disabled { cursor: default; }

.answer-line {
  font-size: 13px;
  color: var(--good);
  margin-bottom: 8px;
  font-weight: 600;
}

.explanation {
  background: var(--panel-2);
  border-left: 3px solid var(--accent-2);
  padding: 10px 14px;
  border-radius: 6px;
  font-size: 14px;
  color: var(--text-dim);
  margin-top: 8px;
  white-space: pre-line;
}
.explanation strong { color: var(--text); }

.toggle-explain-btn, .toggle-lang-btn {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 5px 10px;
  border-radius: 6px;
  font-size: 12px;
  cursor: pointer;
  margin-top: 6px;
}
.toggle-explain-btn:hover, .toggle-lang-btn:hover { border-color: var(--accent); color: var(--text); }

/* Quiz setup */
.quiz-setup-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  max-width: 520px;
  margin: 0 auto;
}
.quiz-setup-card h2 { margin-top: 0; font-size: 18px; }
.form-row { display: flex; flex-direction: column; gap: 6px; margin-bottom: 16px; }
.form-row label { font-size: 13px; color: var(--text-dim); }
.form-row select { width: 100%; }
.pool-info { font-size: 13px; color: var(--text-dim); margin-bottom: 16px; }

.primary-btn {
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  border: none;
  color: white;
  padding: 11px 22px;
  border-radius: 8px;
  font-size: 14px;
  cursor: pointer;
  font-weight: 600;
}
.primary-btn:hover { filter: brightness(1.1); }
.primary-btn:disabled { opacity: 0.5; cursor: not-allowed; }

.secondary-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 11px 22px;
  border-radius: 8px;
  font-size: 14px;
  cursor: pointer;
}
.secondary-btn:hover { border-color: var(--accent); color: var(--text); }

/* Quiz running */
.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 18px;
  gap: 20px;
  flex-wrap: wrap;
}
.quiz-progress { flex: 1; min-width: 200px; }
#quiz-progress-text { font-size: 13px; color: var(--text-dim); }
.progress-bar {
  height: 6px;
  background: var(--panel-2);
  border-radius: 999px;
  overflow: hidden;
  margin-top: 6px;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  width: 0%;
  transition: width .2s ease;
}
.quiz-score { font-size: 14px; color: var(--text-dim); white-space: nowrap; }
.quiz-score span { color: var(--good); font-weight: 700; }

.quiz-nav { display: flex; gap: 10px; margin-top: 18px; flex-wrap: wrap; }

/* Result view */
.result-summary {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  text-align: center;
  margin-bottom: 20px;
}
.result-summary .score-big { font-size: 40px; font-weight: 800; }
.result-summary .score-sub { color: var(--text-dim); margin-top: 6px; }

/* Stats */
.stat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 14px; margin-bottom: 20px; }
.stat-tile {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
}
.stat-tile .stat-num { font-size: 26px; font-weight: 700; }
.stat-tile .stat-label { font-size: 13px; color: var(--text-dim); margin-top: 4px; }

.cat-bar-row { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; font-size: 13px; }
.cat-bar-row .cat-name { width: 160px; flex-shrink: 0; color: var(--text-dim); }
.cat-bar-track { flex: 1; height: 10px; background: var(--panel-2); border-radius: 999px; overflow: hidden; }
.cat-bar-fill { height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent-2)); }
.cat-bar-count { width: 40px; text-align: right; color: var(--text-dim); }

.empty-state { text-align: center; color: var(--text-dim); padding: 60px 20px; }

/* Case studies */
.cs-banner {
  background: rgba(245, 166, 35, 0.1);
  border: 1px solid var(--warn);
  color: var(--text);
  border-radius: var(--radius);
  padding: 14px 18px;
  font-size: 13px;
  line-height: 1.7;
  margin-bottom: 18px;
}
.cs-banner strong { color: var(--warn); }

.sn-module-nav {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 14px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
}
.sn-module-nav .module-btn {
  background: var(--panel-2);
  font-weight: 600;
}
.sn-module-nav .module-btn.active {
  background: linear-gradient(90deg, var(--accent-2), var(--accent));
}

.cs-tabs { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 18px; }
.cs-tab-btn {
  background: var(--panel);
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 8px 16px;
  border-radius: 999px;
  cursor: pointer;
  font-size: 13px;
}
.cs-tab-btn:hover { border-color: var(--accent); color: var(--text); }
.cs-tab-btn.active {
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  color: white;
  border-color: transparent;
}

.cs-detail {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
}
.cs-detail h2 { margin-top: 0; }
.cs-detail .cs-status-note {
  font-size: 13px;
  color: var(--text-dim);
  margin-bottom: 20px;
  padding-bottom: 14px;
  border-bottom: 1px dashed var(--border);
}
.cs-lang-toggle { display: flex; gap: 8px; margin-bottom: 18px; }
.cs-section { margin-bottom: 20px; }
.cs-section h3 { font-size: 15px; color: var(--accent); margin-bottom: 8px; }
.cs-section .cs-section-body { white-space: pre-line; font-size: 14px; color: var(--text); }

@media (max-width: 600px) {
  .cat-bar-row .cat-name { width: 100px; font-size: 12px; }
}