/*
 * ============================================================================
 *  手机端【可隐藏导航栏】（汉堡按钮 + 右侧滑入抽屉菜单）专用样式
 * ----------------------------------------------------------------------------
 *  本文件与 PC 端正常显示的导航栏样式（css/nav.css、css/sub_navbar.css）
 *  完全分离：nav.css / sub_navbar.css 是原版导航，本文件只做手机端覆盖。
 *
 *  ★ 如需整体回退到原版导航（手机端直接缩小显示 PC 横向导航，无抽屉）：
 *    1. 删除 index.html / content.html 中对本文件的 <link ... mobile_nav.css> 引用
 *    2. 删除两个页面中对 js/mobile_nav.js 的 <script> 引用
 *    3. 删除各导航栏 .nav-top 里注释标注的 <button class="nav-toggle"> 汉堡按钮
 *    PC 端样式与本文件无关，删除后不受任何影响。
 * ============================================================================
 */

/* ---- 汉堡按钮（桌面端隐藏，手机端显示） ---- */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 40px;
  height: 36px;
  padding: 6px 8px;
  background: transparent;
  border: none;
  cursor: pointer;
}
.nav-toggle span {
  display: block;
  width: 100%;
  height: 2px;
  background: #fff;
  border-radius: 2px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}
.nav-toggle.open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav-toggle.open span:nth-child(2) {
  opacity: 0;
}
.nav-toggle.open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ---- 桌面端兜底：抽屉结构若残留（JS 未及清理）也不许显示 ---- */
@media screen and (min-width: 1201px) {
  .drawer-head,
  .drawer-close {
    display: none !important;
  }
}

/* ---- 手机端导航覆盖（屏幕宽度 ≤ 1200px 启用抽屉导航） ---- */
@media screen and (max-width: 1200px) {
  /* 顶部栏：logo + 汉堡按钮 */
  .nav-top {
    padding: 0.5rem 1rem;
    margin-top: 0;
  }
  .logo img {
    height: 2.75rem;
  }
  .lang-search,
  .school-name {
    display: none;
  }
  .nav-toggle {
    display: flex;
  }

  /* 首页 hero 里的导航条：改为普通文档流的蓝色横条 */
  .container > .navbar {
    position: static;
    background-color: #1D89EB;
    padding-bottom: 0;
  }

  /* 固定导航栏高度自适应，并置于最上层保证抽屉不被遮挡 */
  .fixed-navbar {
    height: auto;
    z-index: 1002;
  }

  /* 菜单：全屏抽屉，从右侧滑入 */
  .nav-links {
    display: block;
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    background-color: #1D89EB;
    transform: translateX(100%);
    visibility: hidden;
    transition: transform 0.3s ease, visibility 0s linear 0.3s;
    overflow-y: auto;
    z-index: 1001;
    padding-bottom: 2rem;
  }
  .nav-links.open {
    transform: translateX(0);
    visibility: visible;
    transition: transform 0.3s ease;
  }
  body.drawer-open {
    overflow: hidden; /* 抽屉打开时锁定背景滚动 */
  }

  /* 抽屉头部：logo + 关闭按钮（由 js/mobile_nav.js 动态生成） */
  .drawer-head {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.8rem 1rem;
  }
  .drawer-head img {
    height: 2.5rem;
  }
  .drawer-close {
    background: transparent;
    border: none;
    color: #fff;
    font-size: 1.8rem;
    line-height: 1;
    padding: 0.1rem 0.5rem;
    cursor: pointer;
  }

  /* 抽屉内的搜索区（搜索框由脚本从顶栏搬入） */
  .nav-links .lang-search {
    display: flex;
    width: 100%;
    padding: 0.2rem 1rem 1rem;
    gap: 0.55rem;
  }
  .nav-links .search-top {
    align-self: flex-start;
  }
  .nav-links .search-top a {
    color: rgba(255, 255, 255, 0.9);
    font-size: 0.8rem;
  }
  .nav-links .search-box {
    width: 100%;
  }
  .nav-links .search-box input {
    flex: 1;
    width: auto;
    height: 2.2rem;
    border: none;
    border-radius: 1.1rem 0 0 1.1rem;
    padding: 0 1rem;
    font-size: 0.85rem;
  }
  .nav-links .search-box button {
    flex: none;
    width: auto;
    min-width: 2.6rem;
    height: 2.2rem;
    padding: 0 0.8rem;
    border: none;
    border-radius: 0 1.1rem 1.1rem 0;
    background-color: #F39800;
    color: #fff;
    font-size: 0.9rem;
    line-height: 2.2rem;
    white-space: nowrap;
  }

  /* 菜单行：白色文字 + 右侧箭头 + 分隔线 */
  .main-links {
    flex-direction: column;
    flex-wrap: nowrap;
    gap: 0;
  }
  .nav_div > a,
  .nav_div_nob > a {
    position: relative;
    font-size: 1rem;
    padding: 0.95rem 1.2rem;
    text-align: left;
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
  }
  .nav_div:has(ul) > a::after {
    content: "";
    position: absolute;
    right: 1.2rem;
    top: 50%;
    width: 0.5rem;
    height: 0.5rem;
    margin-top: -0.4rem;
    border-right: 2px solid rgba(255, 255, 255, 0.9);
    border-bottom: 2px solid rgba(255, 255, 255, 0.9);
    transform: rotate(45deg);
    transition: transform 0.3s ease;
  }
  .nav_div.open > a::after {
    transform: rotate(225deg);
    margin-top: -0.15rem;
  }

  /* 子菜单：就地展开，小号半透明文字 */
  .nav_div ul {
    position: static;
    opacity: 1;
    visibility: visible;
    transform: none;
    display: none;
    background-color: transparent;
    box-shadow: none;
    border-radius: 0;
    transition: none;
  }
  .nav_div:hover ul {
    display: none;
    opacity: 1;
    visibility: visible;
    transform: none;
  }
  .nav_div.open ul {
    display: block;
  }
  .nav_div ul li {
    border-bottom-color: rgba(255, 255, 255, 0.12);
  }
  .nav_div ul li a {
    color: rgba(255, 255, 255, 0.85);
    font-size: 0.85rem;
    padding: 0.6rem 2rem;
  }
}