void setup()
{
  size(800, 800);
  background(255);
  colorMode(HSB);
}

void draw()
{
  float ypos;
  float diam;
  
  diam = 100;
  
  // clear the screen
  fill(255, 0);
  noStroke();
  rect(0, 0, width, height);
  
  
  // drawing the line
  stroke(random(0, 255), 255, 255);        // line is black
  strokeWeight(2);
  ellipse(random(0, width), random(0, height), diam, diam);
}