body {
    background-color: #000;
    margin: 0;
}

#container {
    background-color: #004e6f;
    position: absolute;
    margin: auto;
    width: 768px;
    height: 512px;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}

canvas {
    position: relative;
    float: left;
    height: 256px;
}

.hidden {
    visibility: hidden;
    position: absolute;
}

#top_canvas {
    z-index: 1;
}

#bottom_canvas {
    -webkit-filter: blur(3px);
    -moz-filter: blur(3px);
    -o-filter: blur(3px);
    -ms-filter: blur(3px);
    filser: blur(3px);
}