void setup(){
  size(400, 400);
  background(0);
  stroke(100,50,255);
  strokeWeight(20);
  smooth();
 }

 int mrX = 0;
 void draw(){

 background(203,240,2);
 point(mrX, 200);
 point(200, mrX);
 mrX = mrX + 80;


 if (mrX > 400){
   mrX = 0;
 }
}