constructor(rate) {

    this.x = floor(random(width));

    this.y = floor(random(height));

    this.r = 2.5;

    this.rate = rate;

  }

​

  display() {

    stroke(255);

    strokeWeight(3);

    fill(255);

    ellipse(this.x, this.y, this.r * 2);

  }

​

  walk() {

    this.x += random(-this.rate, this.rate);

    this.y += random(-this.rate, this.rate);

    this.x = constrain(this.x, 0, width);

    this.y = constrain(this.y, 0, height);

  }

}