// Daniel Shiffman

// http://natureofcode.com

​

// Simple Particle System

​

​

let ps;

​

function setup() {

  createCanvas(900, 900);

  ps = new ParticleSystem(createVector(width / 2, 50));

    noStroke();

}

​

​

function draw() {

  //background(200);

​

  // Option #1 (move the Particle System origin)

  ps.origin.set(mouseX, mouseY, 0);

​

  ps.addParticle();

  ps.run();

​

  // Option #2 (move the Particle System origin)

  // ps.addParticle(mouseX, mouseY);

}

​

​

//Particle Class

class Particle {

​

  constructor(x, y) {

    this.c = color(random(0,255),random(0,255),random(0,255));

    this.acceleration = createVector(0, 0.05);

    this.velocity = createVector(random(-1, 1), random(-2, 0));

    this.position = createVector(x, y);

    this.lifespan = 255.0;

  }

​

  run() {

    this.update();

    this.display();

  }

​

  // Method to update position

  update() {

    this.velocity.add(this.acceleration);

    this.position.add(this.velocity);

    this.lifespan -= 2.0;

  }

​

  // Method to display

  display() {

    //stroke(0, this.lifespan);

    strokeWeight(2);

    this.r = red(this.c);

    this.g = green(this.c);

    this.b = blue(this.c);

    fill(color(this.r,this.g,this.b,this.lifespan));

    ellipse(this.position.x, this.position.y, 12, 12);

  }

​

  // Is the particle still useful?

  isDead() {

    if (this.lifespan < 0.0) {

      return true;

    } else {

      return false;

    }

  }

}

​

//PARTICLE SYSTEM

​

class ParticleSystem {

​

  constructor(x, y) {

    this.origin = createVector(x, y);

    this.particles = [];

  }

​

  addParticle(x, y) {

    if (x !== undefined && y !== undefined) {

      this.particles.push(new Particle(x, y));

    } else {

      this.particles.push(new Particle(this.origin.x, this.origin.y));

    }

  }

​

  run() {

    // Run every particle

    // ES6 for..of loop

    for (let particle of this.particles) {

      particle.run();

    }

​

    // Filter removes any elements of the array that do not pass the test

    this.particles = this.particles.filter(particle => !particle.isDead());

  }

}