/* ============================================================
   在线学习页
   ============================================================ */
.learn-main { padding-bottom: 40px; }

.learn-layout { display: grid; grid-template-columns: 300px 1fr; gap: 20px; align-items: start; }

/* ---------- 左侧目录 ---------- */
.learn-sidebar {
  position: sticky; top: 84px; max-height: calc(100vh - 104px);
  display: flex; flex-direction: column; overflow: hidden;
}
.sidebar-head {
  display: flex; justify-content: space-between; align-items: center;
  padding: 14px 16px; border-bottom: 1px solid var(--border);
  font-weight: 600; font-size: 14px; color: var(--accent);
}
.sidebar-close { display: none; padding: 4px 10px; font-size: 14px; }

.toc-tree { overflow-y: auto; padding: 10px 8px 16px; }

.toc-chapter { margin-bottom: 6px; }
.toc-chapter-btn {
  display: flex; align-items: center; gap: 8px; width: 100%;
  padding: 9px 12px; background: transparent; border: none; cursor: pointer;
  color: var(--text); font-size: 14px; font-weight: 600; border-radius: 8px;
  text-align: left;
}
.toc-chapter-btn:hover { background: rgba(0,164,197,0.05); }
.toc-chapter-btn .arrow { transition: transform 0.2s; color: var(--text-faint); font-size: 11px; }
.toc-chapter.open .toc-chapter-btn .arrow { transform: rotate(90deg); }

.toc-course { padding-left: 8px; display: none; }
.toc-chapter.open .toc-course { display: block; }
.toc-course-item {
  display: block; padding: 7px 12px 7px 14px; border-radius: 8px;
  color: var(--text-muted); font-size: 13px; cursor: pointer;
  border: none; background: transparent; width: 100%; text-align: left;
  display: flex; align-items: center; gap: 8px;
}
.toc-course-item:hover { background: rgba(0,164,197,0.06); color: var(--text); }
.toc-course-item.active { color: var(--accent); background: var(--accent-dim); font-weight: 600; }
.toc-course-item .f-badge {
  font-family: var(--mono); font-size: 11px; color: var(--text-faint);
  background: var(--bg-panel-2); border: 1px solid var(--border);
  border-radius: 4px; padding: 0 5px;
}
.toc-course-item.active .f-badge { color: var(--accent); border-color: rgba(0,164,197,0.3); }
.toc-check { margin-left: auto; color: var(--accent2); font-size: 13px; }

.toc-sections { padding-left: 26px; display: none; }
.toc-course-item.open-toc-sections ~ .toc-sections { display: block; }
.toc-section {
  display: block; padding: 5px 10px; border-radius: 6px;
  color: var(--text-faint); font-size: 12px; cursor: pointer;
  border: none; background: transparent; width: 100%; text-align: left;
}
.toc-section:hover { color: var(--text); }
.toc-section.active { color: var(--accent); }

/* ---------- 右侧内容区 ---------- */
.learn-content { padding: 0; overflow: hidden; }

/* 内容头部 */
.doc-head {
  padding: 26px 30px 20px; border-bottom: 1px solid var(--border);
}
.doc-head h2 { font-size: 22px; margin-bottom: 8px; }
.doc-head .doc-meta { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.doc-head .doc-actions { margin-top: 16px; display: flex; gap: 10px; flex-wrap: wrap; }

/* 内容主体 */
.doc-body { padding: 10px 30px 30px; }
.doc-body h3 {
  font-size: 17px; margin: 26px 0 12px; color: var(--text);
  padding-left: 10px; border-left: 3px solid var(--accent);
}
.doc-body p { color: var(--text); margin: 10px 0; font-size: 14.5px; }
.doc-body ul { margin: 10px 0 10px 22px; }
.doc-body li { color: var(--text); margin: 6px 0; font-size: 14.5px; }
.doc-body table { width: 100%; border-collapse: collapse; margin: 12px 0; font-size: 13.5px; }
.doc-body th, .doc-body td { padding: 8px 12px; text-align: left; border: 1px solid var(--border); }
.doc-body th { background: var(--bg-panel-2); color: var(--accent); }
.doc-body td { color: var(--text); }

/* 提示框 */
.doc-note {
  border-radius: var(--radius-sm); padding: 12px 16px; margin: 14px 0;
  font-size: 13.5px; border-left: 3px solid;
}
.doc-note.info { background: var(--accent-dim); border-color: var(--accent); color: var(--text); }
.doc-note.warn { background: var(--warning-dim); border-color: var(--warning); color: var(--text); }

/* 视频区 */
.video-wrap { margin: 20px 0; border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; background: #000; }
.video-wrap video { width: 100%; display: block; aspect-ratio: 16/9; background: #000; }
.video-fallback {
  display: none; aspect-ratio: 16/9; align-items: center; justify-content: center;
  text-align: center; padding: 20px; color: var(--text-muted);
  background: var(--bg-panel); font-size: 14px;
}
.video-wrap.fallback .video-fallback { display: flex; }
.video-wrap.fallback video { display: none; }
.video-caption { padding: 10px 16px; font-size: 13px; color: var(--text-muted); background: var(--bg-panel); border-top: 1px solid var(--border); }
.video-caption .hl { color: var(--accent); }

/* 节尾操作 */
.section-mark {
  margin-top: 18px; display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 12px 16px; border: 1px dashed var(--border); border-radius: var(--radius-sm);
}
.section-mark .mark-done { color: var(--accent2); font-size: 14px; font-weight: 600; }

/* 已读标记 */
.toc-section .done-mark { color: var(--accent2); float: right; }

/* 内容页内进度 */
.doc-progress {
  height: 4px; background: var(--bg-panel-2); border-radius: 999px; overflow: hidden;
}
.doc-progress > span { display: block; height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent2)); transition: width 0.4s; }

/* 目录抽屉(移动端) */
.toc-mask {
  display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.6); z-index: 60;
}
.toc-mask.show { display: block; }

/* ---------- 响应式 ---------- */
@media (max-width: 900px) {
  .learn-layout { grid-template-columns: 1fr; }
  .learn-sidebar {
    position: fixed; top: 0; left: 0; bottom: 0; width: 300px; max-width: 85vw;
    z-index: 70; border-radius: 0; max-height: none; transform: translateX(-105%);
    transition: transform 0.25s ease;
  }
  .learn-sidebar.show { transform: translateX(0); }
  .sidebar-close { display: inline-flex; }
  .toc-mask.show { display: block; }
}