function setup() {

  createCanvas(400, 400);

  for (let i = 0; i < 40; i++) {

    circles.push(new Circle(random(width), random(height)))

  }

}

​

function draw() {

  background(0);

  circles.forEach(circle => {

    circle.update()

    circle.render()

  })

}

​

class Circle {

  constructor(x, y) {

    this.max = random(30, 80)

    this.r = random(0, 80)

    this.growing = false

    this.x = x

    this.y = y

  }

  update() {

    if (this.r <= 0) {

      this.growing = true

    } else if (this.r >= this.max) {

      this.growing = false

    }

    if (this.growing) {

      this.r+= 0.5

    } else {

      this.r-= 0.5

    }

  }

  render() {

    noStroke()

    ellipse(this.x, this.y, this.r, this.r)

  }

}