/* ============================================
   导航栏 / 返回顶部 / 页脚 样式合集
   1. 导航栏（固定顶部、收缩、隐藏交互）
   2. Logo 样式及hover动效
   3. 移动端汉堡菜单
   4. 导航菜单 & 激活状态
   5. 返回顶部按钮
   6. 页脚样式（响应式 + 渐变线条）
============================================= */

/* ========== 1. 导航栏主体 ========== */
/* 固定顶部导航栏默认状态 */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  padding: 26px 5%;
  background: #ffffff;
  /* 背景模糊效果 */
  backdrop-filter: blur(12px);
  /* flex 横向布局：logo 左、菜单右 */
  display: flex;
  justify-content: space-between;
  align-items: center;
  /* 最高层级，保证在最上层 */
  z-index: 9999;
  /* 平滑过渡动画 */
  transition: all 0.5s cubic-bezier(0.34, 0, 0.2, 1);
  box-shadow: none;
}

/* 滚动后导航栏收缩样式 */
.navbar.shrink {
  padding: 16px 5%;
  box-shadow: none;
}

/* 导航栏向上隐藏样式 */
.navbar.hide {
  transform: translateY(-100%);
  opacity: 0;
}

/* ========== 2. Logo 文字样式 ========== */
.logo {
  font-size: 21px;
  font-weight: 500;
  color: #000;
  letter-spacing: 2.5px;
  cursor: pointer;
  transition: all 0.32s ease;
  position: relative;
  /* 禁止换行 */
  white-space: nowrap;
}

/* Logo 左侧装饰竖线 */
.logo::before {
  content: '';
  position: absolute;
  left: -12px;
  top: 50%;
  transform: translateY(-50%);
  width: 2px;
  height: 16px;
  background: #000;
  opacity: 0.8;
  transition: all 0.3s ease;
}

/* Logo hover 动效：放大 + 字间距加宽 */
.logo:hover {
  transform: scale(1.05);
  letter-spacing: 3px;
}

/* Logo 左侧线条 hover 变高变亮 */
.logo:hover::before {
  height: 22px;
  opacity: 1;
}

/* ========== 3. 汉堡菜单（移动端） ========== */
.hamburger {
  /* 默认隐藏，桌面端不显示 */
  display: none;
  width: 26px;
  height: 20px;
  position: relative;
  background: transparent;
  border: none;
  cursor: pointer;
  /* 比导航更高层级 */
  z-index: 10000;
}

/* 汉堡菜单三条横线 */
.hamburger span {
  position: absolute;
  left: 0;
  width: 100%;
  height: 1.5px;
  background: #222;
  transition: all 0.4s cubic-bezier(0.34, 0, 0.2, 1);
}

.hamburger span:nth-child(1) { top: 0; }
.hamburger span:nth-child(2) { top: 50%; transform: translateY(-50%); }
.hamburger span:nth-child(3) { bottom: 0; }

/* hover 时中间线条缩短 */
.hamburger:hover span:nth-child(2) { width: 70%; }

/* 菜单激活时：变成 X 形状 */
.hamburger.active span:nth-child(1) {
  top: 50%;
  transform: translateY(-50%) rotate(45deg);
}
.hamburger.active span:nth-child(2) { opacity: 0; }
.hamburger.active span:nth-child(3) {
  bottom: 50%;
  transform: translateY(50%) rotate(-45deg);
}

/* ========== 4. 导航菜单列表 ========== */
.nav {
  /* 横向排列 */
  display: flex;
  /* 菜单间距 */
  gap: 50px;
  list-style: none;
  align-items: center;
  flex-shrink: 1;
  min-width: 0;
}

/* 导航链接默认样式 */
.nav li a {
  color: var(--text-light);
  font-size: 18px;
  font-weight: 400;
  text-decoration: none;
  position: relative;
  letter-spacing: 0.4px;
  transition: all 0.35s cubic-bezier(0.25, 0.8, 0.25, 1);
  white-space: nowrap;
}

/* 导航链接 hover 动效 */
.nav li a:hover {
  color: #000;
  font-weight: 500;
  transform: translateY(-2px);
  letter-spacing: 0.8px;
}

/* 强制隐藏下划线 */
.nav li a::after {
  display: none !important;
}

/* 当前页面菜单激活样式 */
.nav li a.active {
  color: #000;
  font-weight: 600;
}

/* 导航内表情默认隐藏 */
.nav li a .emoji {
  display: none;
}

/* ========== 5. 返回顶部按钮 ========== */
.back-top {
  /* 固定在右下角 */
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  /* 圆形 */
  border-radius: 50%;
  background: var(--black-color);
  color: var(--white-color);
  border: none;
  font-size: 20px;
  cursor: pointer;
  /* 默认隐藏 */
  opacity: 0;
  visibility: hidden;
  transition: all 0.32s cubic-bezier(0.34, 0, 0.2, 1);
  z-index: 998;
  /* 居中图标 */
  display: flex;
  align-items: center;
  justify-content: center;
}

/* 显示状态 */
.back-top.show {
  opacity: 1;
  visibility: visible;
}

/* hover 动效 */
.back-top:hover {
  background: #555;
  transform: translateY(-3px) scale(1.05);
  box-shadow: 0 8px 16px rgba(0, 0, 0, 0.12);
}

/* 按下时复位 */
.back-top:active {
  transform: translateY(0);
}

/* ========== 6. 全站页脚样式 ========== */
.footer-full {
  background: var(--black-color);
  color: #e0e0e0;
  /* 响应式内边距 */
  padding: clamp(20px, 5vw, 30px) 0 clamp(15px, 3vw, 20px);
  margin-top: 40px;
  font-weight: 300;
  position: relative;
}

/* 页头顶部渐变分隔线 */
.footer-full::before {
  content: '';
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 70%;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.1), transparent);
  transition: all 0.6s ease;
}

/* hover 时光线变亮 */
.footer-full:hover::before {
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.25), transparent);
}

/* 页脚内容容器 */
.footer-wrap {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 clamp(15px, 3vw, 25px);
  display: flex;
  justify-content: center;
  align-items: center;
  text-align: center;
}

/* 页脚单列布局 */
.footer-col {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
}

/* 页脚标题 */
.footer-col h4 {
  margin: 0;
  font-size: clamp(18px, 3vw, 22px);
  font-weight: 500;
  color: var(--white-color);
  letter-spacing: 1px;
  transition: all 0.3s ease;
}

/* 页脚标题 hover 字间距加宽 */
.footer-col h4:hover {
  letter-spacing: 1.5px;
}

/* 页脚说明文字 */
.footer-col p {
  margin: 0;
  line-height: 1.5;
  font-size: clamp(13px, 2vw, 15px);
  opacity: 0.7;
  letter-spacing: 0.5px;
}

/* ========== 7. 移动端响应式（<768px） ========== */
@media (max-width: 767px) {
  .footer-full {
    padding: clamp(15px, 4vw, 25px) 0;
  }
  .footer-col h4 {
    font-size: clamp(16px, 4vw, 20px);
  }
  .footer-col p {
    font-size: clamp(12px, 3vw, 14px);
  }
}