body {
    padding:0px;
    margin:0px;
    overflow: hidden;
}
#game_area {
    position: fixed;
    display: block;
    left:50%;
    top:50%;
}
#img_rotate{
    position: fixed;
    display: none;
    left:50%;
    top:50%;
}
canvas{
    cursor: pointer;
    /*width: 100%;*/
    height: 100%;
}