/* ==========================================
   Zensical-Chinese-Tutorial 导航层级增强样式
   ========================================== */

/* 一级目录：最顶层，如“笔记” */
.md-nav--primary .md-nav__item--level1 > .md-nav__link {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--md-primary-fg-color, #518FC1);
  border-left: 4px solid var(--md-primary-fg-color, #518FC1);
  padding-left: 0.8rem;
  margin: 0.3rem 0;
  background: linear-gradient(to right, rgba(81, 143, 193, 0.05), transparent);
}

/* 二级目录：数学建模的同级，如“git学习”、“编码(encode)与解码(decode)”等 */
.md-nav--primary .md-nav__list .md-nav__item:not(.md-nav__item--nested) > .md-nav__link,
.md-nav--primary .md-nav__list .md-nav__item--nested > .md-nav__link {
  font-weight: 600;
  font-size: 0.9rem;
  color: #333;
  border-left: 2px solid #8a8a8a;
  padding-left: 1.2rem;
  margin: 0.2rem 0;
}

/* 特别标识“数学建模”这类有子项的二级目录 */
.md-nav--primary .md-nav__list .md-nav__item--nested > .md-nav__link {
  position: relative;
  font-weight: 650; /* 比同级无子项的稍粗 */
  color: #2c5282; /* 深蓝色，区别于普通二级目录 */
}

/* 二级目录有子项的添加小箭头图标 */
.md-nav--primary .md-nav__list .md-nav__item--nested > .md-nav__link::before {
  content: "▶";
  font-size: 0.7em;
  margin-right: 0.5em;
  color: var(--md-primary-fg-color, #518FC1);
  transition: transform 0.2s ease;
}

/* 展开状态的小箭头旋转 */
.md-nav--primary .md-nav__list .md-nav__item--nested.md-nav__item--active > .md-nav__link::before,
.md-nav--primary .md-nav__list .md-nav__item--nested:focus-within > .md-nav__link::before,
.md-nav--primary .md-nav__list .md-nav__item--nested:hover > .md-nav__link::before {
  transform: rotate(90deg);
}

/* 三级目录：如"前言"、"优化模型"等 */
.md-nav--primary .md-nav__list .md-nav__list .md-nav__link {
  font-weight: 500;
  font-size: 0.85rem;
  color: #555;
  border-left: 1px dashed #aaa;
  padding-left: 1.8rem;
  margin: 0.15rem 0;
  opacity: 0.9;
}

/* 四级目录：如"多目标规划"、"层次分析法"等 */
.md-nav--primary .md-nav__list .md-nav__list .md-nav__list .md-nav__link {
  font-weight: 400;
  font-size: 0.8rem;
  color: #777;
  border-left: 1px dotted #ccc;
  padding-left: 2.4rem;
  margin: 0.1rem 0;
  opacity: 0.8;
}

/* 当前活动页面的目录项高亮 */
.md-nav--primary .md-nav__link--active {
  background-color: rgba(81, 143, 193, 0.1) !important;
  color: var(--md-primary-fg-color, #518FC1) !important;
  font-weight: 650 !important;
}

/* 悬停效果增强 */
.md-nav--primary .md-nav__link:hover {
  background-color: rgba(81, 143, 193, 0.05);
  padding-left: calc(1.2rem + 2px); /* 悬停时增加额外缩进 */
  transition: all 0.2s ease;
}

/* 针对您的具体示例，为不同类型的二级目录添加视觉提示 */
/* 有子目录的二级目录（如"数学建模"） */
.md-nav--primary .md-nav__list > .md-nav__item--nested {
  border-bottom: 1px solid #eee;
  padding-bottom: 0.3rem;
  margin-bottom: 0.5rem;
}

/* 无子目录的二级目录（如"git学习"、"编码(encode)与解码(decode)"等） */
.md-nav--primary .md-nav__list > .md-nav__item:not(.md-nav__item--nested) {
  border-bottom: none;
  margin-bottom: 0.3rem;
}