try.css

body {
    background: grey;
}
#canvas {
    background: white;
    position: absolute;
    left: 50%;
    top: 50%;
    margin-left: -350px;
    margin-top: -350px;
    cursor: none;
}
#char {
    position: absolute;
    width: 20px;
    height: 20px;
    background: black
}