body {
            background: url('/bg.gif') repeat center center fixed;
            background-color: black;
            background-size: 100%;
            font-family: Arial, sans-serif;
        }
        .container {
            text-align: center;
            margin-top: 100px;
        }
        button {
            background-color: #ccc;
            color: black;
            padding: 15px 30px;
            margin: 20px;
            border: none;
            border-radius: 5px;
            font-size: 18px;
            cursor: pointer;
        }
        button:hover {
            background-color: #bbb;
        }
        .tip {
            color: white;
            font-size: 16px;
            margin-top: 20px;
        }