var r;

 var g;

 var b;

 var a;

​

//  circle coordinates random everytime-global variable

 var diam;

 var x;

 var y;

​

function setup() {

  createCanvas(400, 400);

  frameRate (0.5)

  // background(255);

}

​

function draw() {

// Each time through draw(), new random 

  // numbers are picked for a new circle.

   r = random(255);

   g = random(255);

   b = random(255);

   a = 50;

   diam = 25;

  // small circles

   fill(r, g, b, a);

  for (var y=0; y <= height; y = y + 20){

    for (var x=0; x <= width; x = x + 20)

    circle(x,y, diam);

  }

  // big circles

  fill(random(255), random(255), random(255), a);

  for (var y=5; y <= height; y = y + 40){

    for (var x=5; x <= width; x = x + 40)

    rect(x,y, 30);

  }

     noStroke();

}

​