body {
       font-family: Arial, Helvetica, sans-serif;
       margin: 0;
       padding: 0;
       background: #444;
       line-height: 1.6;
   }
   header {
       background: #666;
       color: #fff;
       padding: 1rem;
       text-align: center;
   }
   nav {
       background: #222;
       padding: 0.5rem;
       text-align: center;
   }
   nav a {
       color: #fff;
       margin: 0 0.8rem;
       text-decoration: none;
       font-weight: bold;
   }
   nav a:hover { text-decoration: underline; }

   .container {
       max-width: 800px;
       margin: 2rem auto;
       background: #999;
       padding: 1.5rem;
       border-radius: 5px;
       box-shadow: 0 2px 4px rgba(0,0,0,.1);
   }
   h1, h2 { margin-top: 0; }
   ul { list-style: none; padding-left: 0; }
   li { margin-bottom: 0.8rem; }
   li a { color: #0066cc; text-decoration: none; }
   li a:hover { text-decoration: underline; }

   
   table {
       margin: 0 auto;
       border-collapse: collapse;
   }
   table td {
       padding: 3px 20px;
       border: 1px solid;
   }
   table thead {
       background: gray;
   }
   table thead td {
       font-weight: 700;
       border: none
   }
   table thead th {
       padding: 3px 20px;
       border: 1px solid;
   }