jsui (javascript) VERY basic question

hi

my first try to use jsui - I started by editing (a copy of) the 360° dial (the one which is in the help file), and want to get rid of the background (the white square in which is the dial) - to have just the round dial.

If I got it right the colors are in the RGBA values, and when i can change the color of the background, I can not make it disappear

what i do is messing with
var vbrgb = [1.,1.,1.,1];

changing the values of the first 3 params (RGB) works, when the last one (A) does not seem to make any effect

why is it so? any advice?

many thanks

kasper

/*

360 dial

arguments: fgred fggreen fgblue bgred bggreen bgblue dialred dialgreen dialblue

*/

sketch.default2d();
var val = 0;
var vbrgb = [1.,1.,1.,1];
var vfrgb = [0.2,0.2,0.2,1];
var vrgb2 = [0.7,0.7,0.7,1];
var last_x = 0;
var last_y = 0;