var r = 25; // set the radius

var d = 2*r;

var x = r+b;

var y = r+b;

​

function setup() { 

  createCanvas(windowWidth, windowHeight);

  background('white');

  strokeWeight(b);

} 

​

function draw() { 

  stroke(random(255),random(255),random(255));

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

  ellipse(x,y,d,d);

  x += d+b

  if (x > windowWidth) {

    y += d+b;

    x = r+b;

  }

  if (y > windowHeight) {

    x = r+b;

    y = r+b;

  }

}