/* 开启排序模式时，统一卡片样式 */
#chapter-list.reorder-mode .chapter-item,
#chapter-list.reorder-mode .lesson-item {
  border: 2px solid #ddd;
  border-radius: 10px;
  background: #fff;
  cursor: grab;
  transition: box-shadow .2s, border-color .2s;
}

/* 间距与内边距 */
.chapter-item { padding: 8px 10px; margin: 8px 0; }
.lesson-item  { padding: 6px 10px; margin: 6px 0; }

/* hover/active 反馈 */
#chapter-list.reorder-mode .chapter-item:hover,
#chapter-list.reorder-mode .lesson-item:hover {
  border-color: #4CAF50;
  box-shadow: 0 2px 6px rgba(0,0,0,.1);
}
#chapter-list.reorder-mode .chapter-item:active,
#chapter-list.reorder-mode .lesson-item:active {
  cursor: grabbing;
}

.dragging { opacity: .6; }

/* 放置位置提示线（在元素顶部/底部） */
.drop-indicator-top    { box-shadow: inset 0 3px 0 0 #4CAF50; }
.drop-indicator-bottom { box-shadow: inset 0 -3px 0 0 #4CAF50; }

/* 把 lesson 拖到 chapter 标题上时，高亮标题，表示会追加到该章节末尾 */
.chapter-header.drop-target {
  outline: 2px dashed #4CAF50;
  border-radius: 6px;
}
.chapter-header {
    display: block; /* 使元素成为块级元素，占满整行 */
    /* 文字默认左对齐，无需额外设置text-align: left */
  }