for loop

i've done a for loop to put down loads of my stationary discs as mentioned in a previous post but it doesnt seem to work. my for loop is in the init sub class of the control class

disc = new Stationary. 
                
for n=0, n>20, n+=1: {
disc register with-shape (new PolygonDisk init-with radius 0.5 sides 30 height 0.1) at-location (random[20], -5, random[20]).
disc set-color to (1, 0, 1).                
}

cheer
gregger G