/* ═════════════════════════════════════════════════════════════
   DÒ TRẮC NGHIỆM & SO KHỚP ĐÁP ÁN (CHECKER SYSTEM)
   Neo-Scholar & Heritage Design Identity
   ═════════════════════════════════════════════════════════════ */

.checker-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 24px 20px 80px;
}

.checker-header {
  background: linear-gradient(135deg, rgba(30, 41, 59, 0.95) 0%, rgba(15, 23, 42, 0.98) 100%);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 20px;
  padding: 30px;
  margin-bottom: 24px;
  box-shadow: 0 10px 30px -5px rgba(0, 0, 0, 0.35);
  position: relative;
  overflow: hidden;
  color: #f8fafc;
}

.checker-header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, #e11d48, #f59e0b, #10b981, #6366f1);
}

.checker-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: #f59e0b;
  background: rgba(245, 158, 11, 0.12);
  border: 1px solid rgba(245, 158, 11, 0.25);
  padding: 4px 12px;
  border-radius: var(--radius-full);
  margin-bottom: 12px;
}

.checker-heading {
  font-size: 1.85rem;
  font-weight: 800;
  color: #f8fafc;
  margin-bottom: 8px;
  letter-spacing: -0.02em;
}

.checker-subheading {
  color: #94a3b8;
  font-size: 0.95rem;
  line-height: 1.5;
  margin-bottom: 24px;
  max-width: 850px;
}

.checker-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

.checker-select-group {
  display: flex;
  align-items: center;
  gap: 8px;
}

.checker-select-group label {
  font-size: 0.85rem;
  font-weight: 600;
  color: #94a3b8;
}

.checker-select-group select {
  padding: 8px 14px;
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.15);
  background: rgba(15, 23, 42, 0.9);
  color: #f8fafc;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  outline: none;
  transition: all 0.2s ease;
}
.checker-select-group select option {
  background: #0f172a;
  color: #f8fafc;
}

.checker-select-group select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

.checker-tab-pills {
  display: flex;
  gap: 8px;
  background: var(--bg-page);
  padding: 4px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
}

.checker-tab-btn {
  padding: 8px 16px;
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.1);
  background: rgba(15, 23, 42, 0.7);
  color: #94a3b8;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  transition: all 0.2s ease;
}

.checker-tab-btn:hover {
  color: #f8fafc;
}

.checker-tab-btn.active {
  background: rgba(124, 58, 237, 0.25);
  border-color: rgba(124, 58, 237, 0.6);
  color: #c084fc;
}

/* ═════════════════════════════════════════════════════════════
   TAB 1: MATRIX VIEW
   ═════════════════════════════════════════════════════════════ */
.matrix-header-actions {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 12px;
}

.matrix-stats {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.stat-chip {
  padding: 6px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  font-size: 0.85rem;
  color: #94a3b8;
}

.matrix-card {
  background: rgba(30, 41, 59, 0.65);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 18px;
  padding: 24px;
  backdrop-filter: blur(12px);
  margin-bottom: 24px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2);
  color: #f8fafc;
}

.matrix-section-title {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 1.05rem;
  font-weight: 700;
  color: #f8fafc;
  margin-bottom: 20px;
  letter-spacing: -0.01em;
}

.matrix-section-badge {
  font-size: 0.75rem;
  font-weight: 700;
  color: #34d399;
  background: rgba(16, 185, 129, 0.15);
  border: 1px solid rgba(16, 185, 129, 0.3);
  padding: 4px 10px;
  border-radius: 999px;
}

.mcq-matrix-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(95px, 1fr));
  gap: 12px;
}

.mcq-matrix-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 12px 8px;
  background: var(--bg-page);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.mcq-matrix-item:hover {
  transform: translateY(-3px) scale(1.02);
  border-color: var(--primary);
  box-shadow: 0 6px 16px rgba(16, 185, 129, 0.15);
}

.mcq-qnum {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.mcq-ans-pill {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  font-weight: 800;
  color: #fff;
}

.key-A { background: linear-gradient(135deg, #3b82f6, #1d4ed8); }
.key-B { background: linear-gradient(135deg, #10b981, #047857); }
.key-C { background: linear-gradient(135deg, #f59e0b, #b45309); }
.key-D { background: linear-gradient(135deg, #e11d48, #be123c); }

/* TF Matrix Grid */
.tf-matrix-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.tf-matrix-card {
  background: var(--bg-page);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.tf-matrix-card:hover {
  border-color: #f59e0b;
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(245, 158, 11, 0.15);
}

.tf-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.tf-card-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: #f8fafc;
}

.tf-card-lesson {
  font-size: 0.78rem;
  color: var(--text-muted);
}

.tf-statements-key-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
}

.tf-statement-key-chip {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 6px 4px;
  border-radius: 6px;
  font-size: 0.78rem;
  font-weight: 700;
}

.tf-statement-key-chip.is-true {
  background: rgba(16, 185, 129, 0.12);
  color: #10b981;
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.tf-statement-key-chip.is-false {
  background: rgba(239, 68, 68, 0.12);
  color: #ef4444;
  border: 1px solid rgba(239, 68, 68, 0.3);
}

.stmt-letter {
  font-size: 0.72rem;
  opacity: 0.8;
}

.stmt-val {
  font-size: 0.82rem;
  font-weight: 800;
}

/* Detail Box */
.checker-detail-box {
  background: var(--bg-card);
  border: 2px solid var(--primary);
  border-radius: var(--radius);
  padding: 24px;
  margin-top: 24px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.2);
  animation: slideDown 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-12px); }
  to { opacity: 1; transform: translateY(0); }
}

.detail-box-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  border-bottom: 1px solid var(--border);
  padding-bottom: 12px;
}

.close-box-btn {
  background: none;
  border: none;
  font-size: 1.2rem;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px 8px;
}

.detail-opt-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 12px;
  border-radius: 8px;
  margin-bottom: 6px;
  background: var(--bg-page);
}

.detail-opt-item.is-correct {
  background: rgba(16, 185, 129, 0.15);
  border: 1px solid rgba(16, 185, 129, 0.4);
  color: #10b981;
  font-weight: 600;
}

.detail-opt-letter {
  font-weight: 700;
  width: 24px;
}

.detail-exp-box {
  margin-top: 14px;
  padding: 12px;
  background: rgba(99, 102, 241, 0.08);
  border-left: 3px solid #6366f1;
  border-radius: 4px;
  font-size: 0.9rem;
  line-height: 1.5;
}

/* ═════════════════════════════════════════════════════════════
   TAB 2: SELF CHECK (DÒ BÀI TỰ CHẤM)
   ═════════════════════════════════════════════════════════════ */
.selfcheck-guide-banner {
  display: flex;
  align-items: center;
  gap: 16px;
  background: rgba(99, 102, 241, 0.1);
  border: 1px solid rgba(99, 102, 241, 0.25);
  border-radius: var(--radius);
  padding: 18px 24px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.guide-icon { font-size: 1.8rem; }
.guide-text { flex: 1; min-width: 260px; font-size: 0.92rem; line-height: 1.5; color: #f8fafc; }

.selfcheck-score-banner {
  background: linear-gradient(135deg, rgba(16,185,129,0.18), rgba(99,102,241,0.18));
  border: 2px solid var(--primary);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 24px;
  animation: slideDown 0.4s ease;
}

.score-banner-content {
  display: flex;
  align-items: center;
  gap: 20px;
}

.score-trophy { font-size: 3rem; }
.score-highlight { color: var(--primary); font-size: 1.6rem; font-weight: 800; }

.selfcheck-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
}

.selfcheck-row {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  background: var(--bg-page);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: all 0.2s ease;
}

.selfcheck-row.is-row-correct {
  border-color: #10b981;
  background: rgba(16, 185, 129, 0.05);
}

.selfcheck-row.is-row-wrong {
  border-color: #ef4444;
  background: rgba(239, 68, 68, 0.05);
}

.row-qnum {
  font-weight: 700;
  font-size: 0.85rem;
  min-width: 55px;
}

.row-options {
  display: flex;
  gap: 4px;
}

.selfcheck-opt-btn {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: #f8fafc;
  font-weight: 700;
  font-size: 0.82rem;
  cursor: pointer;
  transition: all 0.15s ease;
}

.selfcheck-opt-btn:hover {
  border-color: var(--primary);
  background: var(--primary-soft);
}

.selfcheck-opt-btn.selected {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

.row-feedback {
  margin-left: auto;
  font-size: 0.78rem;
  font-weight: 600;
}

.eval-correct { color: #10b981; }
.eval-wrong { color: #ef4444; }
.eval-blank { color: var(--text-muted); font-size: 0.72rem; }

/* Self check TF */
.selfcheck-tf-container {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.selfcheck-tf-card {
  background: var(--bg-page);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px;
}

.tf-q-title {
  font-weight: 700;
  font-size: 0.95rem;
  margin-bottom: 12px;
  color: #f8fafc;
}

.tf-stmt-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 12px;
  border-bottom: 1px solid var(--border);
  gap: 12px;
}

.stmt-label {
  font-size: 0.88rem;
  flex: 1;
  color: #f8fafc;
}

.stmt-btn-pair {
  display: flex;
  gap: 6px;
}

.tf-toggle-btn {
  padding: 4px 12px;
  font-size: 0.82rem;
  font-weight: 700;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: #94a3b8;
  cursor: pointer;
  transition: all 0.15s ease;
}

.tf-toggle-btn.is-true {
  background: #10b981;
  color: #fff;
  border-color: #10b981;
}

.tf-toggle-btn.is-false {
  background: #ef4444;
  color: #fff;
  border-color: #ef4444;
}

.tf-card-score-eval {
  margin-top: 10px;
  font-size: 0.85rem;
  font-weight: 600;
  color: #f59e0b;
}

/* ═════════════════════════════════════════════════════════════
   TAB 3: EXPLORER VIEW (KHO CÂU HỎI & LỜI GIẢI)
   ═════════════════════════════════════════════════════════════ */
.explorer-search-bar {
  display: flex;
  gap: 12px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.explorer-search-bar input {
  flex: 1;
  min-width: 280px;
  padding: 12px 18px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: #f8fafc;
  font-size: 0.95rem;
  outline: none;
}

.explorer-search-bar input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

.explorer-search-bar select {
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: #f8fafc;
  font-size: 0.9rem;
  cursor: pointer;
}

.explorer-cards-list {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.explorer-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  transition: var(--transition);
}

.explorer-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--border-hover);
}

.explorer-card-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}

.qtype-badge {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 3px 10px;
  border-radius: var(--radius-full);
}

.qtype-badge.mcq {
  background: rgba(99, 102, 241, 0.12);
  color: #6366f1;
}

.qtype-badge.tf {
  background: rgba(245, 158, 11, 0.12);
  color: #f59e0b;
}

.qnum-badge {
  font-weight: 800;
  font-size: 0.9rem;
  color: #f8fafc;
}

.qlesson-badge {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-left: auto;
}

.explorer-q-text {
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.6;
  color: #f8fafc;
  margin-bottom: 16px;
}

/* History Passage antique styling */
.explorer-passage-box {
  display: flex;
  gap: 14px;
  background: rgba(245, 158, 11, 0.05);
  border: 1px solid rgba(245, 158, 11, 0.25);
  border-left: 4px solid #f59e0b;
  border-radius: var(--radius-sm);
  padding: 18px;
  margin-bottom: 18px;
  font-style: italic;
  line-height: 1.7;
}

.passage-icon {
  font-size: 1.5rem;
}

.passage-text {
  flex: 1;
  color: #f8fafc;
}

.explorer-options {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.explorer-opt-row {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  background: var(--bg-page);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}

.explorer-opt-row.is-correct-answer {
  background: rgba(16, 185, 129, 0.12);
  border-color: rgba(16, 185, 129, 0.4);
}

.opt-letter-tag {
  font-weight: 800;
  width: 24px;
  color: #94a3b8;
}

.is-correct-answer .opt-letter-tag {
  color: #10b981;
}

.correct-check {
  margin-left: auto;
  font-size: 0.78rem;
  font-weight: 800;
  color: #10b981;
  letter-spacing: 0.04em;
}

.explorer-explanation {
  margin-top: 14px;
  padding: 12px 16px;
  background: rgba(16, 185, 129, 0.06);
  border-radius: var(--radius-xs);
  font-size: 0.9rem;
  line-height: 1.5;
  color: #94a3b8;
}

/* Explorer TF statement */
.explorer-tf-statements {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.explorer-stmt-row {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  background: var(--bg-page);
  border: 1px solid var(--border);
}

.explorer-stmt-row.stmt-is-true {
  border-left: 3px solid #10b981;
}

.explorer-stmt-row.stmt-is-false {
  border-left: 3px solid #ef4444;
}

.stmt-letter-box {
  font-weight: 800;
  width: 24px;
}

.stmt-text {
  flex: 1;
  font-size: 0.92rem;
  color: #f8fafc;
}

.stmt-status-badge {
  font-size: 0.75rem;
  font-weight: 800;
  padding: 3px 8px;
  border-radius: 4px;
}

.badge-true {
  background: rgba(16, 185, 129, 0.15);
  color: #10b981;
}

.badge-false {
  background: rgba(239, 68, 68, 0.15);
  color: #ef4444;
}

/* Sound button */
.sound-toggle-btn {
  background: var(--bg-gray);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  width: 38px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1rem;
  transition: var(--transition);
}

.sound-toggle-btn:hover {
  background: var(--bg-hover);
  transform: scale(1.05);
}

.sound-toggle-btn.muted {
  opacity: 0.6;
}