let x = 0;

let y=0;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(150);

  rect(x, y, rSize, rSize);

  x = x+1;

  if(x >= width - rSize/2){

  x = 0;

  }

  y = y+6;

  if(y >= width - rSize/2){

  y = 0;

  }

}