html,
body {

    height: 100%;
}

body {

    background: black;
    margin: 0;
    overflow: hidden;
    position: relative;
}

#menu {

    position: absolute;
    z-index: 0;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
}

#start {

    background: 0;
    color: white;
    font-family: consolas;
    border: 2px solid white;
    padding: 20px;
    font-size: 40px;
    cursor: pointer;
}

canvas {

    background: black;
    position: absolute;
    z-index: 1;
}