open window 640,512

label loop
 x=ran(640)
 y=ran(512)
 r=ran(255)
 g=ran(255)
 b=ran(255)
 rad=ran(90)

 for a=rad to 1 step -1
  str=(rad-a+10)/100
  setrgb 1,r*str,g*str,b*str
  fill circle x,y,a
 next a
goto loop
