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

float r;
float g;
float b;
float x;
float y;

void drawScene() {
  r = random(0,255);
  g = random(0,255);
  b = random(0,255);
  background(b,r,g);
}

void drawLines() {
  r = random(0,255);
  g = random(0,255);
  b = random(0,255);
  x = mouseX;
  y = mouseY;
  strokeWeight(5);
  stroke(r,g,b);
  line(0,0,x,y);
  line(0,height/4,x,y);
  line(0,height/2,x,y);
  line(0,3*height/4,x,y);
  line(0,height,x,y);
  line(width/4,height,x,y);
  line(width/2,height,x,y);
  line(3*width/4,height,x,y);
  line(width,height,x,y);
  line(width,3*height/4,x,y);
  line(width,height/2,x,y);
  line(width,height/4,x,y);
  line(width,0,x,y);
  line(3*width/4,0,x,y);
  line(width/2,0,x,y);
  line(width/4,0,x,y);
}

void draw() {
  drawScene();
  drawLines();
}