​

function Particle(x, y) {

  this.x = x;

  this.y = y;

​

  this.yspeed = 0;

​

  this.history = [];

}

​

Particle.prototype.update = function() {

  this.y += this.yspeed;

  this.yspeed += gravity;

​

  if (this.y > height) {

    this.y = height;

    this.yspeed *= -0.9;

  }

​

  var v = createVector(this.x, this.y);

  this.history.push(v);

};

​

Particle.prototype.show = function() {

  stroke(0);

  fill(18, 168, 18);

  ellipse(this.x, this.y, 24, 24);

​

  for (var i = 0; i < this.history.length; i++) {

    var pos = this.history[i];

    ellipse(pos.x, pos.y, 8, 8);

  }

​

  if (this.history.length > 25) {

    this.history.splice(0, 1);

  }

};

​

​

var particle;

setup = function() {

  createCanvas(400, 400);

  particle = new Particle(100, 100);

}

​

draw = function() {

  background(200);

  particle.update();

  particle.show();

};