gn: center;
            }
            .output {
                height: 300px;
                text-align: center;
            }
            .spacer {
                height: 20px;
            }
            svg {
                display: block;
                margin: auto;
            }
            rect.btn {
                stroke: #ffffff;
                fill: #ffffff;
                fill-opacity: 0;
                stroke-opacity: 0;
            }
        </style>
    </head>
    <body>
        <table