void setup(){

  size(300,300);

}
void loop(){

  if(mousePressed){
    background(255);
    ellipse(mouseX-15,mouseY-15,30,30);
    line(0,0,mouseX,mouseY);
    line(300,0,mouseX,mouseY);
  }else{fill(mouseY,mouseX,200);
    ellipse(mouseX-10,mouseY-10,mouseX,20);
  }

}