/* ================= 核心变量与基础 ================= */
    :root { 
      --darker: #020617;     /* 最深背景 */
      --card-bg: #0f172a;    /* 卡片背景 */
      --border: #1e293b;     /* 边框线 */
      --accent: #8b5cf6;     /* 主题强调色 (紫色) */
      --accent-hover: #a78bfa; 
      --text: #cbd5e1;       /* 正文文字 */
      --text-muted: #64748b; /* 辅助文字 */
    }
    body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; background: var(--darker); color: var(--text); margin: 0; line-height: 1.6; }
    a { text-decoration: none; color: inherit; transition: all 0.3s ease; }
    
    /* ================= 头部与分类导航 ================= */
    .header { padding: 20px; text-align: center; border-bottom: 1px solid var(--border); background: rgba(2, 6, 23, 0.8); backdrop-filter: blur(10px); position: sticky; top: 0; z-index: 50; }
    .logo { font-size: 24px; font-weight: 900; color: #f8fafc; letter-spacing: 1px; }
    .logo span { color: var(--accent); }
    
    /* 新增：分类模块 */
    .nav-categories { max-width: 1000px; margin: 20px auto 10px; padding: 0 20px; display: flex; justify-content: center; flex-wrap: wrap; gap: 12px; }
    .nav-categories a { display: inline-block; padding: 8px 20px; background: var(--card-bg); border: 1px solid var(--border); border-radius: 30px; font-size: 14px; font-weight: 500; color: var(--text); }
    .nav-categories a:hover, .nav-categories a.active { background: var(--accent); border-color: var(--accent); color: #fff; box-shadow: 0 0 15px rgba(139,92,246,0.3); transform: translateY(-2px); }

    /* ================= 主体内容区 ================= */
    .viewer { max-width: 1000px; margin: 0 auto; text-align: center; padding: 20px; }
    .viewer h1 { font-size: 24px; color: #f8fafc; margin-top: 0; margin-bottom: 10px; line-height: 1.4; }
    .meta-info { font-size: 14px; color: var(--text-muted); margin-bottom: 25px; display: flex; justify-content: center; gap: 15px; flex-wrap: wrap; }
    
    /* 图片与翻页 */
    .img-box { position: relative; margin-bottom: 30px; }
    .img-box img { max-width: 100%; height: auto; box-shadow: 0 10px 30px rgba(0,0,0,0.5); border-radius: 8px; cursor: pointer; border: 1px solid var(--border); transition: transform 0.3s ease; }
    .img-box img:hover { transform: scale(1.01); border-color: rgba(139,92,246,0.5); box-shadow: 0 10px 40px rgba(139,92,246,0.15); }
    
    .btn-group { display: flex; justify-content: center; gap: 20px; margin: 30px 0; }
    .btn { padding: 12px 35px; border-radius: 30px; font-size: 15px; font-weight: 600; background: var(--card-bg); border: 1px solid var(--border); color: var(--text); }
    .btn:hover { background: #1e293b; color: #fff; }
    .btn.next { background: var(--accent); border-color: var(--accent); color: #fff; box-shadow: 0 4px 15px rgba(139,92,246,0.3); }
    .btn.next:hover { background: var(--accent-hover); border-color: var(--accent-hover); box-shadow: 0 6px 20px rgba(139,92,246,0.5); transform: translateY(-2px); }
    
    /* ================= SEO 文章阅读模块 ================= */
    .seo-box { background: var(--card-bg); border: 1px solid var(--border); border-radius: 12px; padding: 30px; text-align: left; position: relative; margin-bottom: 40px; }
    .seo-title { font-size: 18px; margin: 0 0 20px 0; color: #f8fafc; display: flex; align-items: center; gap: 8px; font-weight: bold; }
    .seo-title::before { content: ""; display: block; width: 4px; height: 18px; background: var(--accent); border-radius: 2px; }
    
    .seo-content { font-size: 15px; color: var(--text); line-height: 1.8; max-height: 180px; overflow: hidden; transition: max-height 0.5s cubic-bezier(0.4, 0, 0.2, 1); }
    .seo-content p { margin: 0 0 12px 0; text-indent: 2em; text-align: justify; }
    
    /* 暗黑渐变遮罩 */
    .seo-mask { position: absolute; bottom: 80px; left: 0; width: 100%; height: 100px; background: linear-gradient(to bottom, rgba(15,23,42,0), rgba(15,23,42,1)); pointer-events: none; border-radius: 0 0 12px 12px; }
    
    .seo-action { text-align: center; margin-top: 20px; position: relative; z-index: 2; }
    .seo-btn { display: inline-flex; align-items: center; gap: 5px; padding: 8px 28px; background: transparent; border: 1px solid var(--accent); border-radius: 30px; color: var(--accent); font-size: 14px; font-weight: 500; cursor: pointer; transition: all 0.3s ease; user-select: none; }
    .seo-btn:hover { background: var(--accent); color: #fff; box-shadow: 0 0 15px rgba(139,92,246,0.4); }

    /* ================= 底部链接矩阵 ================= */
    .text-matrix { background: var(--card-bg); border: 1px solid var(--border); border-radius: 12px; padding: 30px; text-align: left; margin-bottom: 40px; }
    .text-matrix h3 { font-size: 18px; color: #f8fafc; margin-top: 0; margin-bottom: 20px; display: flex; align-items: center; gap: 8px; }
    .text-matrix h3::before { content: ""; display: block; width: 4px; height: 18px; background: var(--accent); border-radius: 2px; }
    
    .text-matrix-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 12px; }
    .text-matrix a { display: block; padding: 12px 15px; background: rgba(2,6,23,0.4); border: 1px solid var(--border); border-radius: 8px; font-size: 14px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; transition: 0.3s; }
    .text-matrix a::before { content: "▸"; margin-right: 8px; color: var(--accent); font-weight: bold; }
    .text-matrix a:hover { background: var(--accent); border-color: var(--accent); color: #fff; padding-left: 20px; }
    
    /* 页脚 */
    .footer { text-align: center; padding: 30px 20px; color: var(--text-muted); font-size: 14px; border-top: 1px solid var(--border); }
    .footer a { color: var(--text); margin: 0 10px; }
    .footer a:hover { color: var(--accent); }

    /* 移动端适配 */
    @media(max-width: 600px) {
      .header { padding: 15px; }
      .viewer { padding: 15px; }
      .viewer h1 { font-size: 20px; }
      .nav-categories { padding: 0 10px; gap: 8px; }
      .nav-categories a { padding: 6px 16px; font-size: 13px; }
      .btn { padding: 10px 25px; }
      .seo-box, .text-matrix { padding: 20px; }
      .text-matrix-grid { grid-template-columns: 1fr; }
    }