body {
    display: flex;
    flex-direction: column;
    align-items: center;
    overflow: hidden;
}

input {
    display: inline-block;
    width: auto;
    text-align: center;
}

canvas {
    margin: 0;
    position: fixed;
    top: 50%;
    left: 50%;
    width: 100vmin;
    height: 100vmin;
    transform: translate(-50%, -50%);
    z-index: -1;
}

pre {
    padding: 0.3em;
    background: rgb(255, 255, 255, 0.8);
}