function setup() {

  createCanvas(400, 400); //create the canvas

  frameRate(1); //draw slow

}

function draw() {

  num =  pow(2,x); //num = 2^x 

  fill(random(255),random(255),random(255));//randomize color

  circle(200,y1,num)//draw circle with 2^x diameter

  text('2',x*20,12);//write 2 and have it move left with each circle

  text('x',x*20-10,12);//write x and have it move left with each circle

  fill(255)//make a white rectangle diameter text

  rect(330,0,100,20)//rectangle for diameter text

  fill(0)//make the text black

  text(str(num),350,12)//diamter text box

  x = x+1;//increase the exponent by 1

  y1 = y1+12;//move the center of the circle down 12 

  if(x == 11){//make sure that the animation loops and doesn't crash

    x = 0;//reset x

    y1 = 100;//reset y

    background(255)//reset background

  } 

}