/* 侧边栏 */
.course-details {
    position: fixed; top:0; right:-360px; width:360px; height:100%;
    background:#fff; box-shadow:-2px 0 10px rgba(0,0,0,.1);
    transition:right .3s ease; padding:16px; overflow:auto; z-index: 1000;
  }
  .course-details.open { right:0; }
  .details-header { display:flex; justify-content:space-between; align-items:center; }
  .close-btn { border:none; background:transparent; font-size:22px; cursor:pointer; }
  
  /* 主体布局 */
  .lesson-editor { display:flex; height: calc(100vh - 20px); gap: 12px; padding: 12px; }
  .outline {
    width: 280px; border:1px solid #eee; border-radius:10px; padding:10px;
    overflow:auto; background:#fafafa;
  }
  .outline-header { font-weight:700; margin-bottom:8px; }
  #outline-tree { list-style:none; padding-left:0; }
  #outline-tree li { margin:4px 0; cursor:pointer; }
  #outline-tree .lvl1 { font-weight:700; }
  #outline-tree .lvl2 { margin-left:12px; }
  #outline-tree .lvl3 { margin-left:24px; }
  #outline-tree li.active { background:#eaf6ff; border-radius:6px; padding:2px 6px; }
  
  .editor-pane {
    flex:1; display:flex; flex-direction:column; min-width:0;
    border:1px solid #eee; border-radius:10px;
  }
  .editor-tabs { display:flex; align-items:center; gap:8px; padding:8px; border-bottom:1px solid #eee; }
  .tab-btn { border:1px solid #ddd; background:#fff; padding:6px 10px; border-radius:8px; cursor:pointer; }
  .tab-btn.active { background:#f0f8ff; border-color:#a0c4ff; }
  .actions { margin-left:auto; }
  .actions button { padding:6px 12px; border:none; border-radius:8px; background:#4CAF50; color:#fff; cursor:pointer; }
  .tab-content { flex:1; padding:8px; }
  .tab { display:none; height:100%; }
  .tab.active { display:block; height:100%; }
  textarea {
    width:100%; height: calc(100vh - 180px);
    border:1px solid #ddd; border-radius:8px; padding:10px; font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
    box-sizing:border-box; resize: vertical;
  }