  padding-left: 3pt;
    font-size: 16pt;
}

button {
    width: 108pt;
    height: 28pt;
    margin-left:4pt;
    margin-right:4pt;
    font-size: 16pt;
}
    </style>
    <script language="JavaScript">

// client
var w = 640.0;
var h = 512.0;

// visible region
var x_min = -1.0;
var y_min = -1.0;
var x_max = 9.0;
var y_max = 7.0;

var client_x_center = w*(0-x_min)/(x_max-x_min);
var client_x_step = (w/(x_max-x_min));

var client_y_center = h - h*(0-y_min)/(y_max-y_min);
var client_y_step = (h/(y_max-y_min