let xSpeed=12;

​

​

​

function setup() {

  createCanvas(400, 400);

  noStroke();

  rectMode(CENTER);

  frameRate(10);

  background(250);

}

​

function draw() {

  //background(255);

​

  fill(random(255),255,0);

  rect(xPosition,width/2,100,100);

  //

​

  fill(255,random(255),255);

  rect(xPosition,width/4,random(50,100),100);

  //

  fill(random(255),255,255);

  rect(xPosition,width-(width/4),random(50,100),100);

  xPosition += xSpeed;

  if(xPosition > width || xPosition <0){

   xSpeed *= -1;  

  }

}