void setup(){
  size(500,500);

  //randomise lines based on width of window.
  float l1 = random(width);
  float l2 = random(width-l1)+l1;
  float l3 = random(width-l2)+l2;

  //vertical lines
  stroke(0,0,255);
  line(l1,height,l1,0);
  stroke(0,255,0);
  line(l2,height,l2,0);
  stroke(255,0,0);
  line(l3,height,l3,0);

  //horizontal lines
  float l1h1 = random(height);
  float l1h2 = random(height);
  float l1h3 = random(height);

  stroke(0,0,255);
  line(0,l1h1,l1,l1h1);
  stroke(0,255,0);
  line(0,l1h2,l1,l1h2);
  stroke(255,0,0);
  line(0,l1h3,l1,l1h3);

}