body {
            font-family: Arial, sans-serif;
        }
        #chart_container {
            margin: 20px auto;
            width: 800px;
        }
        .subtitle {
            text-align: center;
            font-size: 12px;
            color: #666;
            margin-top: -20px;
            margin-bottom: 20px;
        }
        .footer {
            text-align: center;
            font-size: 12px;
            margin-top: 10px;
        }