Particle System Deconstructed

The Sketch
Cloud
Particle
 
let clouds;
let particles;
​
function setup() {
  createCanvas(windowWidth, windowHeight);
  background(66, 170, 245);
  clouds = [];
  particles = [];
  for(let i = 0; i < 20; i++) {
    clouds.push(new Cloud(random(width), random(height)));
  }
  for(let i = 0; i < 100; i++) {
    particles.push(new Particle());
  }
}
​
function draw() {
  {
    for(let i = 0; i < clouds.length; i++) {
      background(66, 170, 245);
      clouds[i].display();
    }
  }
  background(66, 170, 245);
  {
    for(let i = 0; i < particles.length; i++) {
      particles[i].move();
      particles[i].display();
    }
  }
  
  particles.filter((that) => {
    return that.x > 0 && that.x < width && that.y > 0 && that.y < height
  });
}