let vel = [];

let diameter = [];

const NUM = 100;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  frameRate(60);

  for (let i = 0; i < NUM; i++) {

    loc[i] = createVector(width / 2, height / 2);

    vel[i] = createVector(random(-10, 10), random(-10, 10));

    diameter[i] = random(10, 40);

  }

}

​

function draw() {

  background(0);

  noStroke();

  fill(0, 127, 255);

  for (let i = 0; i < NUM; i++) {

    loc[i].add(vel[i]);

    circle(loc[i].x, loc[i].y, diameter[i]);

    if (loc[i].x < 0 || loc[i].x > width) {

      vel[i].x = vel[i].x * -1;

    }

    if (loc[i].y < 0 || loc[i].y > height) {

      vel[i].y = vel[i].y * -1;

    }

  }

}

​