html,
body {
    height: 100%;
    min-height: 100%;
    margin: 0;
    padding: 0;
}

canvas {
    display: block;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    padding: 0;
    margin: auto;
}

.button {
    /* display: inline-flex; */
     position: absolute; */
    top: 10px;
    /* left: 10px; */
    margin: 10px;
    z-index: 1000;
}