constructor() {

    this.x = random(width);

    this.y = -30;

    this.diam = random(15, 30);

    this.yVel = random(2, 5);

    this.color = 255;

  }

}

​

let circles = [];

​

let numCircles = 20;

​

function setup() {

  createCanvas(400, 400);

  for (let d = 0; d < numCircles; d += 1) {

    let aCircle = new Circle();

    circles.push(aCircle);

  }

}

​

function draw() {

  background(120);

​

  // for each circle:

  for (let d = 0; d < circles.length; d += 1) {

    let aCircle = circles[d];

​

    // draw

    fill(aCircle.color);

    ellipse(aCircle.x, aCircle.y, aCircle.diam, aCircle.diam);

​

    // update

    aCircle.y += aCircle.yVel;

​

    // check

    if (aCircle.y > height) {

      aCircle.y = -30;

    }

  }

}

​