#seamless_preview {
    width: 100%;
    height: 512px;
    background: black;
}

#download_button {
    display: block;
    margin-left: auto;
    margin-right: auto;
    line-height: 50px;
    height: 50px;
    width: 300px;
    text-align: center;
    background: lightblue;
    border-style: outset;
}
#download_button:hover{
    background: lightskyblue;
    cursor: pointer;
    border-style: outset;
}

#download_button:active{
    background: lightslategray;
    border-style: inset;
}

#canvas {
    width: 512px;
    height: 512px;
    display: block;
    margin-left: auto;
    margin-right: auto;
    background: black;
    border-style: outset;
}

html,
body {
    width: 100%;
    height: 100%;
    margin: 0;
}