/* =========================================
   页眉布局 (Header & Navigation)
   ========================================= */

.site-header {
  height: 80px;
  background-color: var(--bg-body);
  border-bottom: 1px solid var(--border-muted);
  position: sticky; /* 粘性定位，确保始终置顶 */
  top: 0;
  z-index: 1000;
  backdrop-filter: blur(12px);          /* 毛玻璃效果 */
  -webkit-backdrop-filter: blur(12px);
  /* 使用半透明背景以增强毛玻璃效果 */
  background-color: rgba(255, 255, 255, 0.85);
  transition: background-color var(--duration-normal), border-color var(--duration-normal), transform 0.45s var(--ease-in-out);
  will-change: transform;
  flex-shrink: 0; /* 防止被父容器 Flex 布局压缩 */
}

.site-header .container {
  height: 100%; /* 关键修复：让容器撑满 Header 高度，使内部 flex 垂直居中生效 */
}

[data-theme="dark"] .site-header {
  background-color: rgba(13, 17, 23, 0.85);
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 100%;
}

/* --- Logo 区域 --- */
.logo-container,
.logo-link {
  display: flex;
  align-items: center;
  height: 100%;
}

.logo-main {
  height: 58px;
  width: auto;
  display: block;
}

.logo-main-dark {
  display: none;
}

[data-theme="dark"] .logo-main-light {
  display: none;
}

[data-theme="dark"] .logo-main-dark {
  display: block;
}

.logo-mobile {
  display: none;
  height: 48px;
  width: auto;
}

/* --- 主导航 (Navigation) --- */
.main-navigation {
  display: flex;
  align-items: center;
  gap: 24px;
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: 8px; /* 菜单项间距 */
  margin: 0;
  padding: 0;
}

.nav-menu a {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 16px; /* 增大导航字号 (原15px) */
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  transition: all var(--duration-fast);
  display: flex;
  align-items: center;
}

.nav-menu a:hover,
.nav-menu a:focus {
  color: var(--text-primary);
  background-color: var(--bg-surface);
}

/* --- 社交链接与工具 (Social & Tools) --- */
.social-links {
  display: flex;
  align-items: center;
  gap: 12px;
  padding-left: 12px;
  margin-left: 12px;
  border-left: 1px solid var(--border-muted);
}

.social-links a,
.theme-toggle,
.lang-toggle {
  width: 40px; /* 增大图标按钮尺寸 (原36px) */
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  background: transparent;
  border: 1px solid transparent; /* 预留边框位置防止抖动 */
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--duration-fast);
}

.social-links a:hover,
.theme-toggle:hover,
.lang-toggle:hover {
  background-color: var(--bg-surface);
  color: var(--color-primary);
  border-color: var(--border-default);
}

/* --- 主题切换动画 (Theme Toggle) --- */
.theme-toggle {
  position: relative; /* 为内部 SVG 绝对定位做准备 */
  overflow: hidden;
}

.theme-toggle svg {
  position: absolute;
  transition: transform 0.5s var(--ease-in-out), opacity 0.5s;
}

/* 默认 / 浅色模式状态: 显示月亮 (提示切换到深色) */
/* 修正逻辑：通常浅色模式下，按钮为了表示“点击切换到深色”，会显示月亮；
   但也有一种逻辑是显示“当前是太阳”。
   根据之前的代码意图，我们从 CSS 变量来看：
   浅色模式下，.moon-icon 显示，.sun-icon 隐藏 */

/* 浅色模式下：太阳隐藏 */
html:not([data-theme="dark"]) .sun-icon {
  opacity: 0;
  transform: rotate(90deg) scale(0);
}

/* 浅色模式下：月亮显示 */
html:not([data-theme="dark"]) .moon-icon {
  opacity: 1;
  transform: rotate(0) scale(1);
}

/* 深色模式下：太阳显示 */
[data-theme="dark"] .sun-icon {
  opacity: 1;
  transform: rotate(0) scale(1);
}

/* 深色模式下：月亮隐藏 */
[data-theme="dark"] .moon-icon {
  opacity: 0;
  transform: rotate(-90deg) scale(0);
}

/* 语言切换按钮文字 */
.lang-toggle {
  font-weight: 600;
  font-size: 15px; /* 增大切换字号 (原14px) */
  width: auto;
  padding: 0 12px;
}

/* --- 移动端菜单开关 (Hamburger) --- */
.mobile-menu-toggle {
  display: none; /* 默认隐藏 */
  flex-direction: column;
  justify-content: space-between;
  width: 24px;
  height: 18px;
  background: transparent;
  border: none;
  cursor: pointer;
  z-index: 1100;
  padding: 0;
}

.mobile-menu-toggle span {
  display: block;
  width: 100%;
  height: 2px;
  background-color: var(--text-secondary);
  border-radius: 2px;
  transition: all 0.3s var(--ease-in-out);
  transform-origin: left center;
}

/* 激活状态 (X 形状) */
.mobile-menu-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translate(0px, -2px);
  width: 115%;
}
.mobile-menu-toggle.active span:nth-child(2) {
  opacity: 0;
  transform: translateX(-10px);
}
.mobile-menu-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translate(0px, 2px);
  width: 115%;
}

/* --- 响应式适配 --- */
@media (max-width: 900px) {
  .logo-main {
    display: none;
  }

  .logo-main.logo-main-dark {
    display: none;
  }

  .logo-mobile {
    display: block;
  }

  .mobile-menu-toggle {
    display: flex;
    order: 2; /* 放在最右侧 */
  }

  .nav-menu {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--bg-body);
    border-bottom: 1px solid var(--border-default);
    flex-direction: column;
    padding: 1rem;
    gap: 0;

    /* 默认收起状态 */
    opacity: 0;
    transform: translateY(-10px);
    pointer-events: none;
    transition: all var(--duration-normal) var(--ease-in-out);
    box-shadow: var(--shadow-md);
    z-index: 1000;
  }

  .nav-menu.active {
    opacity: 1;
    transform: translateY(0);
    pointer-events: auto;
  }

  .nav-menu a {
    width: 100%;
    padding: 12px 16px;
    justify-content: flex-start;
  }

  /* 移动端隐藏社交分割线 */
  .social-links {
    border-left: none;
    margin-left: auto; /* 推到右侧 */
    order: 1; /* 放在 toggle 左侧 */
    margin-right: 12px; /* 和 toggle 之间增加一点间距 */
  }
}