/* ========== 顶部导航 ========== */
html {
  margin: 0; /* 清除默认外边距 */
  height: 100%; /* 让 body 占满视口高度 */
}
section {
  padding: 50px 0;
  margin: auto;
}
.section-title {
  font-size: 36px;
  margin-bottom: 10px;
  padding-left: 6vw;
  text-transform: uppercase;
}
.section-title:lang(zh) {
  font-size: 30px; /* 中文大小 */
}
header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 44px;
  background: #fff;
  border-bottom: 1px solid #fff;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
  z-index: 1000;
}
*,
*::before,
*::after {
  box-sizing: border-box;
}
body {
  margin: 0;
  height: 100%;
  display: flex;
  flex-direction: column;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Open Sans", sans-serif;
  background: #fff;
  color: #000;
}
html {
  scroll-behavior: smooth;
}
.logo {
  font-size: 20px;
  font-weight: bold;
}
h1,
h2,
h3,
p,
ul,
li,
a {
  margin: 0;
  padding: 0;
  list-style: none; /* 列表无默认符 */
  text-decoration: none; /* 链接无下划线 */
  color: inherit; /* 继承父级文字颜色 */
}
nav ul {
  display: flex;
  gap: 30px;
  justify-content: center;
}
nav ul li {
  position: static;
}
nav > ul > li:has(.submenu) {
  position: relative; /* 设置定位基准 */
}
nav ul li a {
  display: block;
  padding: 10px 0;
  font-size: 12px;
  transition: color 0.2s;
}
nav ul li a:hover,
nav ul li a.active {
  color: #0071e3;
}
@media (max-width: 700px) {
  nav > ul {
    display: none !important;
  }
}
nav ul li a.active::after {
  content: '';
  position: absolute;
  bottom: 6px;
  left: 0;
  right: 0;
  height: 2px;
  background: #0071e3;
}
.icons {
  display: flex;
  align-items: center;
  gap: 15px;
}
/* ========== 背景蒙层模糊 ========== */
.overlay {
  position: fixed;
  top: 44px;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(255,255,255,0.6);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  visibility: hidden;
  opacity: 0;
  transition: opacity 0.4s ease-out 0.4s, visibility 0.4s ease-out 0.4s;
  z-index: 900;
  pointer-events: none; /* 添加此行，修复菜单隐藏问题 */
}
.overlay.active {
  visibility: visible;
  opacity: 1;
}
nav ul li:hover > .overlay {
  visibility: visible;
  opacity: 1;
  transition: opacity 0.4s ease-out 0s, visibility 0s;
/* visibility 立即可见，无 transition */
  pointer-events: auto; /* 显示时启用交互 */
}
/* ========== 二级菜单 ========== */
.submenu {
  position: fixed;
  top: 40px; /* 紧贴导航下方 */
  left: 0;
  width: 100vw; /* 填满整个视口宽度 */
/* width: max-content; 宽度按内容自适应 */
  background: #fff;
  backdrop-filter: blur(0px); /* 背景再次模糊 */
  box-shadow: 0 10px 30px rgba(0,0,0,0);
  padding: 20px 0;
  visibility: hidden;
  opacity: 0;
  pointer-events: none;
  transform: translateY(-10px); /* NEW: Start position for slide-down */
  transition: opacity 0.3s ease-out 0.3s, transform 0.3s ease-out 0.3s, visibility 0.4s ease-out 0.4s; /* NEW: Add transform transition for slide */
  z-index: 1001;
  max-height: calc(100vh - 44px); /* 最大高度为视口剩余 */
  overflow-y: auto; /* 内容超出时滚动 */
}
nav ul li:hover > .submenu {
  visibility: visible;
  opacity: 1;
  transform: translateY(0);
  transition: opacity 0.3s ease-out 0s, transform 0.3s ease-out 0s, visibility 0s;
/* visibility 立即可见，无 transition */
  pointer-events: auto; /* 显示时启用交互 */
}
.submenu-content {
  display: flex;
  grid-template-columns: 1fr 1fr 1fr;
  max-width: 1200px;
  margin: 28px auto 28px calc(50vw - 326px);
  gap: 150px;
  opacity: 0;
  pointer-events: none;
  transform: translateY(-10px);
  transition: opacity 0.3s ease-out 0.1s, transform 0.3s ease-out 0.1s;
  will-change: transform, opacity;
  transform: translateY(-10px);
}
.parent-menu:hover .submenu {
  opacity: 1;
  transform: translateY(0);
}
/* 菜单项通用样式 */
.submenu-column li {
  opacity: 0;
  transform: translateY(-10px); /* 改为垂直方向：初始位置向上偏移 */
  transition: opacity 0.4s ease, transform 0.4s ease;
}
/* 按左上到右下顺序设置动画延迟 */
/* 第一列 */
.submenu-column:nth-child(1) li:nth-child(1) {
  transition-delay: 0.03s;
}
.submenu-column:nth-child(1) li:nth-child(2) {
  transition-delay: 0.06s;
}
.submenu-column:nth-child(1) li:nth-child(3) {
  transition-delay: 0.09s;
}
/* 第二列 */
.submenu-column:nth-child(2) li:nth-child(1) {
  transition-delay: 0.15s;
}
.submenu-column:nth-child(2) li:nth-child(2) {
  transition-delay: 0.18s;
}
.submenu-column:nth-child(2) li:nth-child(3) {
  transition-delay: 0.21s;
}
/* 第三列 */
.submenu-column:nth-child(3) li:nth-child(1) {
  transition-delay: 0.27s;
}
.submenu-column:nth-child(3) li:nth-child(2) {
  transition-delay: 0.3s;
}
.submenu-column:nth-child(3) li:nth-child(3) {
  transition-delay: 0.33s;
}
.submenu-column:nth-child(3) li:nth-child(4) {
  transition-delay: 0.36s;
}
/* 鼠标悬停时触发动画 */
nav ul li:hover > .submenu .submenu-column li {
  opacity: 1;
  transform: translateY(0);
}
nav ul li:hover > .submenu .submenu-content {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}
.submenu-column h3 {
  font-size: 8px;
  text-transform: uppercase;
  font-weight: 300;
  margin-bottom: 8px;
  color: #555;
}
.submenu-column ul {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.submenu-column:first-child ul li a {
  font-size: 18px;
  font-weight: bold;
  line-height: 0.8;
}
.submenu-column:not(:first-child) ul li a {
  font-size: 13px;
  line-height: 0.8;
  font-weight: 600;
}
/* ========== 主体内容模糊 ========== */
.blur {
  filter: blur(5px);
  transition: filter 0.4s ease-out 0.4s, visibility 0.4s ease-out 0.4s;
}
main.blur {
  filter: blur(5px);
}
/* 确保模糊层是二级菜单的直接兄弟元素 */
.blur-overlay {
  position: fixed;
  top: 44px; /* 从导航栏下方开始覆盖 */
  left: 0;
  width: 100vw;
  height: calc(100vh - 44px); /* 扣除导航栏高度 */
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px); /* Safari兼容 */
  background: rgba(255,255,255,0.2);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease 0.3s;
  z-index: 999; /* 低于二级菜单（1001）但高于主内容 */
  pointer-events: none; /* 避免遮挡下方交互 */
}
/* 修正触发逻辑：当二级菜单显示时激活模糊层 */
nav ul li:hover > .submenu + .blur-overlay {
  opacity: 1;
  visibility: visible;
  transition: opacity 0.3s ease 0s, visibility 0s;
/* visibility 立即可见，无 transition */
}
/* Mobile Menu Styles */
.mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 20px;
  cursor: pointer;
  color: #000;
}
@media (max-width: 700px) {
  .mobile-menu-toggle {
    display: block;
  }
  section {
    padding: 50px 0px;
  }
}
.mobile-menu {
  position: fixed;
  top: 44px;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(255,255,255,0.8);
  backdrop-filter: blur(20px);
  box-shadow: 0 10px 30px rgba(0,0,0,0.1);
  padding: 20px;
  visibility: hidden;
  grid-column: 1/-1;
  opacity: 0;
  transform: translateY(-100%);
  transition: opacity 0.4s ease-out 0s, transform 0.4s, visibility 0.4s step-end 0.4s;
  z-index: 1001;
  max-height: calc(100vh - 44px);
  overflow-y: auto;
}
.mobile-menu.active {
  visibility: visible;
  opacity: 1;
  transform: translateY(0);
  transition: opacity 0.4s ease-out 0s, transform 0.4s ease-out 0s, visibility 0s;
}
.mobile-menu ul {
  height: 100%;
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.mobile-menu ul li {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  gap: 8px;
}
.mobile-menu ul li a {
  font-size: 18px;
  font-weight: bold;
  line-height: 0.8;
  display: block;
  padding: 10px 0;
  transition: color 0.2s;
}
.mobile-menu ul li a:hover,
.mobile-menu ul li a.active {
  color: #0071e3;
}
.mobile-submenu {
  padding-left: 20px;
  display: none;
  flex-direction: column;
  gap: 10px;
  grid-column: 1/-1;
}
.mobile-submenu.open {
  display: flex;
}
.mobile-submenu li a {
  font-size: 13px;
  font-weight: 600;
  line-height: 0.8;
}
.mobile-menu h3 {
  font-size: 12px;
  text-transform: uppercase;
  font-weight: 600;
  margin-bottom: 8px;
  color: #555;
}
.submenu-toggle {
  border: 0;
  background: none;
  cursor: pointer;
  padding: 6px 10px;
  font-size: 16px;
  line-height: 1;
  color: inherit; /* 跟随文字颜色 */
  transition: transform 0.2s ease;
}
.submenu-toggle[aria-expanded="true"] {
  transform: rotate(180deg); /* 展开时旋转 */
}
.submenu-toggle .chevron {
  width: 1em; /* 跟随字体大小缩放 */
  height: 1em;
  display: block;
  stroke: currentColor; /* 用当前文字颜色 */
  fill: none;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
  vector-effect: non-scaling-stroke; /* 旋转/缩放时笔画保持像素粗细 */
  transition: transform 0.2s ease;
}
.submenu-toggle[aria-expanded="true"] .chevron {
  transform: rotate(180deg);
}
footer {
  background: #f5f5f7;
  text-align: center;
  padding: 40px 20px;
  font-size: 12px;
  color: #444;
}
.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 20px;
  justify-content: center;
  margin-bottom: 20px;
}
.footer-links ul {
  min-width: 120px;
}
@media (prefers-color-scheme: dark) {
  header {
    background: #1e1e1e;
    border-bottom: 1px solid rgba(255,255,255,0);
  }
  body {
    background: #1c1c1e; /* Dark background */
    color: #fff; /* Light text */
  }
  .overlay {
    background: rgba(0,0,0,0.6);
    -webkit-backdrop-filter: blur(10px);
    backdrop-filter: blur(10px);
  }
  .submenu {
    background: #1e1e1e;
    -webkit-backdrop-filter: blur(0px);
    backdrop-filter: blur(0px);
    box-shadow: 0 10px 30px rgba(255,255,255,0);
  }
  .submenu-column h3 {
    color: #aaa;
  }
  footer {
    background: #121212;
    color: #ccc;
  }
  nav ul li a:hover,
  nav ul li a.active {
    color: #4da0ff;
  }
  .mobile-menu {
    background: #1e1e1e;
    box-shadow: 0 10px 30px rgba(255,255,255,0.1);
  }
  .mobile-menu h3 {
    color: #aaa;
  }
  .submenu-toggle {
    color: #ddd;
  }
  .mobile-menu-toggle {
    color: #fff;
  }
  .blur-overlay {
    position: fixed;
    top: 44px; /* 从导航栏下方开始覆盖 */
    left: 0;
    width: 100vw;
    height: calc(100vh - 44px); /* 扣除导航栏高度 */
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px); /* Safari兼容 */
    background: rgba(30,30,30,0.2);
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.4s ease-out 0.4s;
    z-index: 999; /* 低于二级菜单（1001）但高于主内容 */
    pointer-events: none; /* 避免遮挡下方交互 */
  }
}