html,
body {
                margin: 0;
                text-align: center;
                background: #111;
            }

#fullscreen {
                position: fixed;
                top: 0;
                right: 0;
                bottom: 0;
                left: 0;
                display: flex;
                justify-content: center;
                align-items: center;
            }

            #fullscreen canvas {
                object-fit: contain;
                max-height: 100%;
                max-width: 100%;
            }