constructor(xStart, yStart) {

    this.x = xStart;

    this.y = yStart;

    this.xVelocity = random(-1, 1);

    this.yVelocity = random(-5, -1);

    this.alpha = 255;

  }

  update() {

    this.x += this.xVelocity;

    this.y += this.yVelocity;

    this.alpha -= 5;

  }

  disappeared() {

    return this.alpha <= 0;

  }

  show() {

    noStroke();

    fill(233, this.alpha);

    ellipse(this.x, this.y, 16);

  }

}

​

let particles;

​

function setup() {

  createCanvas(400, 400);

  particles = [];

}

​

function draw() {

  background(22);

  particles.push(new Particle((mouseX) ? mouseX : width / 2, (mouseY) ? mouseY : height - 50));

  for (let i = particles.length - 1; i >= 0; i--) {

    particles[i].update();

    particles[i].show();

    if (particles[i].disappeared())

      particles.splice(i, 1);

  }

}