// declare global variables
int x = 100;
int speed = 5;

void setup() {
  size(400, 400);
  smooth();
}
void draw() 
{
  background(255);

  
  //change x by speed
  x = x + speed;
  
  // if we've reached an edge, reverse speed
  
  if ((x > 330) || (x < 75))
  {
                              
    
    speed = speed * -1;
  } 
  
  // display circle at x location
  stroke(0);
  background(0);
  fill(175);
  ellipse(x, 345, 32, 32);
  fill(0, 255, 0);
  rect(340, 100, 10, 350);
  rect(50, 100, 10, 350);
}