/* 手機螢幕的特殊設定 */
  @media (max-width: 600px) {
    nav {
      width: 100%;
      box-sizing: border-box;
      padding: 0;
    }
    
    nav ul li {
      margin: 0 10px; 
      font-size: 1.1rem; 
    }
  
    /* 限制網頁上所有的圖片寬度，不得超過螢幕 */
    img {
      max-width: 100%;
      height: auto; /* 確保圖片縮放時不會變形 */
    }
   
    .category {
      width: 90%; 
      box-sizing: border-box;
      padding: 10px; 
      margin: 15px 10px; 
    }

  }
  
    body {
      background-color: #f9f9f9;
      margin: 0;
      padding: 0;
      font-size:  1.6rem; /* 全站基準字體大小 */ 
    }
    h1 {
      text-align: center;
      color: #333;
      padding: 20px 0;
      font-size: 2rem; 
    }
    h1 a {
      text-decoration: none; 
      color: inherit;
    }
    
    
    /* 導覽列樣式 */
    nav {
      background-color: #0066cc;
      padding: 10px;
      position: sticky;
      top: 0;
      z-index: 300;
      font-size: 1.6rem; 
    }
    nav ul {
      list-style-type: none;
      margin: 0;
      padding: 0;
      display: flex;
      justify-content: center;
    }
    nav li {
      margin: 0 25px;
      font-size: 1.6rem; 
    }
    nav a {
      color: #fff;
      text-decoration: none;
      font-weight: bold;
    }
    nav a:hover {
      text-decoration: underline;
    }
    
    .category {
      background: #fff;
      border: 1px solid #ddd;
      border-radius: 8px;
      margin: 20px auto;
      padding: 15px;
      max-width: 600px;
      box-shadow: 0 2px 5px rgba(0,0,0,0.1);
      font-size: 1.3rem; 
    }
    .category h2 {
      font-size: 1.3rem; 
      color: #0066cc;
      margin-bottom: 10px;
    }
    .category h3 {
      font-size: 1.3rem; 
      color: #333;
      margin-bottom: 2px;
      font-weight: 400;
    }
    .category ul {
      list-style-type: none;
      padding: 0;
    }
    .category li {
      margin: 28px 0;
      font-size: 1.3rem; 
    }
    .category a {
      text-decoration: none;
      color: #333;
      font-weight: 400;
    }
    .category a:hover {
      color: #0066cc;
    }
    
    .subtitle {
      display: block;          
      font-size: 0.9em;        
      color: #1E756D;          
      margin-left: 0px ;    
      font-weight: 400;
    }
    
    .sub-links {
       display: none; /* 預設隱藏 */
       margin: 10px 10px;
       font-size: 1em;    
    }

    .sub-links li {
       margin: 10px 10px;
       font-size: 1em;
       letter-spacing: 20px !important;
    }  
    
    .sub-links li b {
      color: #0055AB;
      letter-spacing: 0px !important;
    }
    
    .sub-links a {
      text-decoration: none;
      color: #0055AB;
      font-size: 1em;
      letter-spacing: 0px !important;
    }
    
    
   /* 回到頂端按鈕樣式 */
    #topBtn {
      display: none; /* 預設隱藏 */
      position: fixed;
      bottom: 30px;
      right: 30px;
      z-index: 100;
      font-size: 16px;
      border: none;
      outline: none;
      background-color: #0066cc;
      color: white;
      cursor: pointer;
      padding: 10px 15px;
      border-radius: 5px;
      box-shadow: 0 2px 5px rgba(0,0,0,0.3);
    }
    #topBtn:hover {
      background-color: #004a99;
    }