* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: -apple-system, "Microsoft YaHei", sans-serif; background: #f0f2f5; color: #1a1a2e; }

.app { max-width: 960px; margin: 0 auto; padding: 0 20px 30px; }

header {
  text-align: center;
  margin: 0 -20px 28px;
  padding: 32px 20px 24px;
  background: linear-gradient(135deg, #1D4ED8 0%, #2563EB 40%, #3B82F6 100%);
  border-radius: 0 0 20px 20px;
  box-shadow: 0 4px 20px rgba(29,78,216,0.3);
  position: relative;
}
header h1 { font-size: 26px; color: #ffffff; margin-bottom: 18px; letter-spacing: 1px; text-shadow: 0 2px 4px rgba(0,0,0,0.15); }

nav { display: flex; gap: 8px; justify-content: center; flex-wrap: wrap; }
.nav-btn {
  padding: 9px 22px;
  border: 1px solid rgba(255,255,255,0.35);
  border-radius: 8px;
  background: rgba(255,255,255,0.12);
  color: #fff;
  cursor: pointer;
  font-size: 14px;
  backdrop-filter: blur(4px);
  transition: background 0.2s, border-color 0.2s;
}
.nav-btn:hover { background: rgba(255,255,255,0.22); border-color: rgba(255,255,255,0.55); }
.nav-btn.active { background: rgba(255,255,255,0.95); color: #1D4ED8; border-color: #fff; font-weight: 600; }
.nav-btn:disabled { opacity: 0.5; cursor: not-allowed; }

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

.qa-input-area { display: flex; gap: 8px; margin-bottom: 16px; }
#qa-input { flex: 1; padding: 12px 16px; border: 1px solid #d0d5dd; border-radius: 8px; font-size: 15px; background: #fff; }
#qa-input:focus { outline: none; border-color: #3B82F6; box-shadow: 0 0 0 3px rgba(59,130,246,0.15); }
#qa-send { padding: 12px 28px; background: linear-gradient(135deg, #22C55E, #16A34A); color: white; border: none; border-radius: 8px; cursor: pointer; font-size: 15px; font-weight: 600; box-shadow: 0 2px 8px rgba(34,197,94,0.3); }
#qa-send:hover { background: linear-gradient(135deg, #16A34A, #15803D); }

.qa-results { background: white; border-radius: 12px; padding: 24px; min-height: 200px; max-height: none; overflow: visible; box-shadow: 0 2px 12px rgba(0,0,0,0.06); border: 1px solid #e8ecf0; }
.qa-results .answer-card { max-height: none; overflow: visible; }

.qa-hints { display: flex; gap: 6px; flex-wrap: nowrap; overflow-x: auto; margin-bottom: 12px; padding-bottom: 4px; -webkit-overflow-scrolling: touch; }
.qa-hints::-webkit-scrollbar { height: 3px; }
.qa-hints::-webkit-scrollbar-thumb { background: #d0d5dd; border-radius: 2px; }
.qa-hint-tag { white-space: nowrap; flex-shrink: 0; padding: 4px 14px; background: #eef4ff; color: #2563EB; border-radius: 14px; font-size: 12px; cursor: pointer; border: 1px solid #d0e0ff; user-select: none; }
.qa-hint-tag:hover { background: #2563EB; color: white; }

.welcome { text-align: center; color: #4a5568; line-height: 2; }
.welcome ul { display: inline-block; text-align: left; margin: 8px 0; }
.welcome li { list-style: none; padding: 4px 0; }

.answer-card { line-height: 1.7; }
.answer-card .core { font-size: 16px; margin-bottom: 16px; padding: 16px 20px; background: #eef4ff; border-radius: 8px; border-left: 4px solid #3B82F6; word-break: break-word; line-height: 1.8; }
.answer-card .section { margin-bottom: 14px; }
.answer-card .section h3 { font-size: 14px; color: #2563EB; margin-bottom: 6px; }
.answer-card .section ul { padding-left: 20px; }
.answer-card .section li { margin-bottom: 4px; }
.answer-card .source { margin-top: 16px; padding-top: 12px; border-top: 1px solid #e8ecf0; font-size: 13px; color: #9ca3af; }

.placeholder { text-align: center; color: #999; padding: 60px 0; font-size: 16px; }

/* ===== 题库 ===== */
.qb-tabs { display: flex; gap: 4px; margin-bottom: 16px; }
.qb-tab { padding: 8px 18px; border: 1px solid #d0d5dd; border-radius: 8px 8px 0 0; background: #f0f2f5; cursor: pointer; font-size: 14px; color: #4a5568; }
.qb-tab.active { background: white; border-bottom-color: white; font-weight: 600; color: #1D4ED8; }
.qb-mode { display: none; }
.qb-mode.active { display: block; }

.qb-filters { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; margin-bottom: 12px; }
.qb-filters select, .qb-filters input { padding: 6px 10px; border: 1px solid #d0d5dd; border-radius: 6px; font-size: 13px; background: #fff; }
.qb-filters select:focus, .qb-filters input:focus { outline: none; border-color: #3B82F6; box-shadow: 0 0 0 3px rgba(59,130,246,0.12); }
.qb-filters button { padding: 6px 20px; background: linear-gradient(135deg, #22C55E, #16A34A); color: white; border: none; border-radius: 6px; cursor: pointer; font-weight: 600; box-shadow: 0 2px 6px rgba(34,197,94,0.25); }
.qb-filters button:hover { background: linear-gradient(135deg, #16A34A, #15803D); }
.qb-filters label { font-size: 13px; display: flex; align-items: center; gap: 4px; color: #4a5568; }

.qb-stats { padding: 8px 14px; background: #eef4ff; border-radius: 8px; font-size: 13px; margin-bottom: 12px; color: #2563EB; border: 1px solid #d0e0ff; }

.qb-card { background: white; border: 1px solid #e8ecf0; border-radius: 10px; padding: 16px; margin-bottom: 10px; box-shadow: 0 1px 4px rgba(0,0,0,0.04); }
.qb-card .qb-meta { font-size: 12px; color: #9ca3af; margin-bottom: 6px; }
.qb-card .qb-content { font-size: 15px; line-height: 1.6; margin-bottom: 8px; color: #1a1a2e; }
.qb-card .qb-options { font-size: 13px; color: #4a5568; padding-left: 12px; margin-bottom: 6px; }
.qb-card .qb-options div { padding: 2px 0; }
.qb-card .qb-answer { color: #16A34A; font-size: 13px; font-weight: bold; margin-top: 6px; }
.qb-card .qb-explain { color: #4a5568; font-size: 13px; margin-top: 4px; padding: 8px; background: #f8fafc; border-radius: 6px; border-left: 3px solid #3B82F6; }
.qm-del-btn { margin-top: 8px; padding: 4px 14px; border: 1px solid #ffccc7; border-radius: 4px; font-size: 12px; cursor: pointer; background: #fff2f0; color: #ff4d4f; }
.qm-del-btn:hover { background: #ffccc7; }

#st-chapters label { display: inline-block; margin: 4px 8px 4px 0; font-size: 14px; cursor: pointer; }

/* ===== 课程资源库 ===== */
.mt-tabs { display: flex; gap: 4px; margin-bottom: 16px; }
.mt-tab { padding: 8px 18px; border: 1px solid #d0d5dd; border-radius: 8px 8px 0 0; background: #f0f2f5; cursor: pointer; font-size: 14px; color: #4a5568; }
.mt-tab.active { background: white; border-bottom-color: white; font-weight: 600; color: #1D4ED8; }
.mt-view { display: none; }
.mt-view.active { display: block; }

.mt-filters { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; margin-bottom: 12px; }
.mt-filters select, .mt-filters input, .mt-filters button { padding: 6px 10px; border: 1px solid #d0d5dd; border-radius: 6px; font-size: 13px; }
.mt-filters button { background: linear-gradient(135deg, #22C55E, #16A34A); color: white; border: none; cursor: pointer; padding: 6px 20px; font-weight: 600; box-shadow: 0 2px 6px rgba(34,197,94,0.25); }
.mt-filters button:hover { background: linear-gradient(135deg, #16A34A, #15803D); }
.mt-filters input { flex: 1; }

.mt-chapter-card { background: white; border: 1px solid #e8ecf0; border-radius: 10px; margin-bottom: 6px; overflow: hidden; box-shadow: 0 1px 4px rgba(0,0,0,0.04); }
.mt-ch-header { padding: 12px 16px; cursor: pointer; display: flex; align-items: center; gap: 12px; user-select: none; }
.mt-ch-header:hover { background: #f8fafc; }
.mt-ch-title { font-size: 15px; font-weight: 600; flex: 1; color: #1a1a2e; }
.mt-ch-stats { font-size: 12px; color: #9ca3af; }
.mt-ch-arrow { color: #9ca3af; font-size: 12px; transition: transform 0.2s; }
.mt-ch-body { padding: 0 16px 12px; display: none; }

.mt-group { margin-bottom: 12px; }
.mt-group h4 { font-size: 13px; color: #2563EB; margin-bottom: 6px; padding-bottom: 4px; border-bottom: 1px solid #e8ecf0; }
.mt-group ul { list-style: none; padding: 0; }
.mt-group li { padding: 4px 0; font-size: 13px; display: flex; align-items: center; gap: 8px; }
.mt-file-icon { font-size: 16px; }
.mt-file-teacher { font-size: 11px; color: #9ca3af; background: #f0f2f5; padding: 1px 6px; border-radius: 4px; }
.mt-file-path { font-size: 11px; color: #c4c8cc; }

.mt-kp-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.mt-kp-tag { padding: 3px 10px; background: #eef4ff; color: #2563EB; border-radius: 12px; font-size: 12px; cursor: pointer; border: 1px solid #d0e0ff; }
.mt-kp-tag:hover { background: #2563EB; color: white; }

.mt-result-card { background: white; border: 1px solid #e8ecf0; border-radius: 8px; padding: 12px; margin-bottom: 8px; }
.mt-result-header { display: flex; align-items: center; gap: 8px; margin-bottom: 4px; }
.mt-result-title { font-weight: 600; font-size: 14px; color: #1a1a2e; }
.mt-result-meta { display: flex; gap: 12px; font-size: 12px; color: #9ca3af; margin-bottom: 4px; }
.mt-result-path { font-size: 11px; color: #c4c8cc; margin-bottom: 4px; }
.mt-result-kps { font-size: 12px; color: #2563EB; }

.mt-locate-section { margin-bottom: 16px; padding: 12px; background: white; border-radius: 8px; border: 1px solid #e8ecf0; }
.mt-locate-section h4 { font-size: 14px; color: #2563EB; margin-bottom: 8px; }
.mt-locate-item { padding: 4px 0; font-size: 13px; line-height: 1.6; }

/* ===== 课件总览 ===== */
.mt-section-header { background: white; border-radius: 10px; padding: 16px; margin-bottom: 12px; border: 1px solid #e8ecf0; }
.mt-section-header h3 { font-size: 16px; margin-bottom: 10px; color: #1a1a2e; }
.mt-filter-bar { display: flex; gap: 8px; flex-wrap: wrap; }
.mt-filter-bar select { padding: 6px 10px; border: 1px solid #d0d5dd; border-radius: 6px; font-size: 13px; background: #fff; }

.cw-item { display: flex; align-items: center; gap: 8px; padding: 6px 0; font-size: 13px; border-bottom: 1px solid #f0f2f5; }
.cw-item:last-child { border-bottom: none; }
.cw-icon { font-size: 18px; flex-shrink: 0; }
.cw-title { flex: 1; color: #1a1a2e; }
.cw-meta { font-size: 11px; color: #9ca3af; background: #f0f2f5; padding: 1px 6px; border-radius: 4px; }

.mt-summary-bar { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; padding: 8px 14px; background: #eef4ff; border-radius: 8px; font-size: 13px; margin-bottom: 12px; color: #2563EB; border: 1px solid #d0e0ff; }
.mt-summary-tag { background: white; padding: 2px 8px; border-radius: 10px; font-size: 11px; color: #2563EB; border: 1px solid #d0e0ff; }

/* ===== 知识图谱 ===== */
.kg-container {  }
.kg-search-bar { display: flex; gap: 8px; margin-bottom: 12px; }
.kg-search-bar input { flex: 1; padding: 8px 12px; border: 1px solid #d0d5dd; border-radius: 6px; font-size: 14px; background: #fff; }
.kg-search-bar input:focus { outline: none; border-color: #3B82F6; box-shadow: 0 0 0 3px rgba(59,130,246,0.12); }
.kg-search-bar button { padding: 8px 20px; background: linear-gradient(135deg, #22C55E, #16A34A); color: white; border: none; border-radius: 6px; cursor: pointer; font-weight: 600; box-shadow: 0 2px 6px rgba(34,197,94,0.25); }
.kg-search-bar button:hover { background: linear-gradient(135deg, #16A34A, #15803D); }

.kg-layout { display: flex; gap: 16px; }
.kg-sidebar { width: 280px; flex-shrink: 0; background: white; border-radius: 10px; padding: 12px; border: 1px solid #e8ecf0; max-height: 600px; overflow-y: auto; }
.kg-main { flex: 1; min-width: 0; }

.kg-tree-item { padding: 8px 10px; border-radius: 6px; cursor: pointer; margin-bottom: 4px; border: 1px solid transparent; }
.kg-tree-item:hover { background: #eef4ff; }
.kg-tree-item.active { background: #eef4ff; border-color: #3B82F6; }
.kg-tree-header { display: flex; align-items: center; gap: 8px; }
.kg-tree-title { font-size: 13px; font-weight: 600; flex: 1; color: #1a1a2e; }
.kg-tree-stats { font-size: 11px; color: #9ca3af; white-space: nowrap; }
.kg-tree-kps { display: flex; flex-wrap: wrap; gap: 3px; margin-top: 4px; }
.kg-kp-tag { font-size: 10px; padding: 1px 6px; background: #eef4ff; color: #2563EB; border-radius: 8px; }

.kg-stats { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 12px; }
.kg-stat { font-size: 12px; padding: 4px 10px; background: #eef4ff; border-radius: 6px; color: #4a5568; }

.kg-sub-tabs { display: flex; gap: 4px; margin-bottom: 8px; }
.kg-sub-tab { padding: 6px 14px; border: 1px solid #d0d5dd; border-radius: 6px 6px 0 0; background: #f0f2f5; cursor: pointer; font-size: 13px; color: #4a5568; }
.kg-sub-tab.active { background: white; border-bottom-color: white; font-weight: 600; color: #1D4ED8; }
.kg-sub-content { background: white; border: 1px solid #e8ecf0; border-radius: 0 8px 8px 8px; padding: 12px; min-height: 150px; margin-bottom: 12px; }
.kg-sub-view { display: none; }
.kg-sub-view.active { display: block; }

.kg-kp-card { display: inline-block; padding: 8px 14px; margin: 4px; background: #eef4ff; border-radius: 8px; border: 1px solid #d0e0ff; }
.kg-kp-name { font-size: 13px; font-weight: 600; color: #2563EB; }
.kg-kp-meta { font-size: 11px; color: #9ca3af; margin-top: 2px; }

.kg-item-card { padding: 8px 10px; margin-bottom: 4px; border: 1px solid #e8ecf0; border-radius: 6px; }
.kg-item-card:hover { background: #f8fafc; }
.kg-item-title { font-size: 13px; color: #1a1a2e; }
.kg-item-meta { font-size: 11px; color: #9ca3af; margin-top: 2px; }
.kg-item-actions { display: flex; gap: 6px; margin-top: 6px; }
.kg-item-actions button { padding: 3px 10px; border: 1px solid #d0d5dd; border-radius: 4px; font-size: 11px; cursor: pointer; background: white; }
.kg-item-actions button:hover { background: #eef4ff; }
.kg-btn-view { color: #2563EB; }
.kg-btn-dl { color: #16A34A; font-weight: 600; }
.kg-btn-rename { color: #f0ad4e; font-weight: 600; }
.kg-btn-move { color: #6B7280; font-weight: 700; font-size: 14px; }
.kg-btn-del { color: #ff4d4f; font-weight: 600; }

/* 图谱搜索结果浮层 */
.kg-search-result { background: white; border: 1px solid #3B82F6; border-radius: 10px; padding: 14px; margin-bottom: 12px; box-shadow: 0 2px 16px rgba(59,130,246,0.12); }
.kg-sr-header { font-size: 15px; font-weight: 600; margin-bottom: 10px; color: #1D4ED8; }
.kg-sr-section { font-size: 12px; margin-bottom: 6px; line-height: 1.7; }
.kg-sr-label { font-weight: 600; color: #4a5568; margin-right: 6px; flex-shrink: 0; }
.kg-sr-tag { display: inline-block; padding: 1px 8px; background: #eef4ff; color: #2563EB; border-radius: 8px; font-size: 11px; margin: 1px 2px; }
.kg-sr-close { font-size: 12px; color: #9ca3af; cursor: pointer; margin-top: 8px; text-align: right; }
.kg-sr-close:hover { color: #1a1a2e; }

/* ── 课程视频 ── */
.video-container { background: white; border-radius: 12px; padding: 20px; box-shadow: 0 2px 12px rgba(0,0,0,0.06); border: 1px solid #e8ecf0; }
.video-tabs { display: flex; gap: 8px; margin-bottom: 16px; }
.video-tab { padding: 8px 20px; border: 1px solid #d0d5dd; border-radius: 8px; background: white; cursor: pointer; font-size: 14px; color: #4a5568; }
.video-tab.active { background: linear-gradient(135deg, #1D4ED8, #3B82F6); color: white; border-color: transparent; box-shadow: 0 2px 8px rgba(29,78,216,0.3); }
.video-panel { display: none; }
.video-panel.active { display: block; }
.video-placeholder { text-align: center; padding: 40px 20px; }
.video-btn { display: inline-block; padding: 12px 28px; background: linear-gradient(135deg, #1D4ED8, #3B82F6); color: white; border-radius: 8px; text-decoration: none; font-size: 16px; font-weight: 600; box-shadow: 0 4px 12px rgba(29,78,216,0.25); }
.video-btn:hover { background: linear-gradient(135deg, #1e40af, #2563EB); }

/* ── 管理员登录按钮（左上角） ── */
.admin-login-btn {
  position: absolute;
  top: 10px;
  left: 14px;
  padding: 5px 14px;
  border: 1px solid rgba(255,255,255,0.4);
  border-radius: 6px;
  background: rgba(255,255,255,0.15);
  color: #fff;
  cursor: pointer;
  font-size: 13px;
  backdrop-filter: blur(4px);
  transition: background 0.2s;
}
.admin-login-btn:hover { background: rgba(255,255,255,0.3); }
.modal-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.45); display: flex; align-items: center; justify-content: center; z-index: 1000; }
.modal { background: white; border-radius: 14px; padding: 24px; width: 400px; box-shadow: 0 12px 40px rgba(0,0,0,0.2); }
.modal-input { width: 100%; padding: 10px 12px; border: 1px solid #d0d5dd; border-radius: 6px; font-size: 14px; box-sizing: border-box; background: #fff; }
.modal-input:focus { outline: none; border-color: #3B82F6; box-shadow: 0 0 0 3px rgba(59,130,246,0.12); }
.modal-btn { padding: 8px 20px; border: none; border-radius: 6px; cursor: pointer; font-size: 14px; font-weight: 600; }
.modal-btn-primary { background: linear-gradient(135deg, #1D4ED8, #3B82F6); color: white; box-shadow: 0 2px 8px rgba(29,78,216,0.25); }
.modal-btn-primary:hover { background: linear-gradient(135deg, #1e40af, #2563EB); }
.modal-btn-cancel { background: #f0f2f5; color: #4a5568; border: 1px solid #d0d5dd; }
.modal-btn-cancel:hover { background: #e4e7eb; }