let paints = [];
let numPaints = 5000;
let gravity;

function setup() {
  createCanvas(windowWidth, windowHeight);
  for (let i = 0; i < numPaints; i++) {
    paints.push(new Paint());
  }
  gravity = createVector(0, random(-.1, .1));
}

function draw() {
  background = color(random(100, 256), random(100, 256), random(100, 256));

  for (let i = 0; i < paints.length; i++) {
    let p = paints[i];
    p.applyForce(gravity);
    p.update();
    p.show();
    p.fade();

    if (p.isOffScreen()) {
      paints[i] = new Paint();
    }
  }
}

class Paint {
  constructor() {
    this.position = createVector(random(width * 5), random(height * 5));
    this.velocity = createVector(random(-1, 1), random(1, 1));
    this.acceleration = createVector(0);
    this.color = color(random(100, 256), random(100, 256), random(100, 256));
    this.opacity = random(0,1);
  }

  applyForce(force) {
    this.acceleration.add(force);
  }

  update() {
    this.velocity.add(this.acceleration);
    this.position.add(this.velocity);
    this.acceleration.mult(.01);
  }

  show() {
    stroke(this.color, this.opacity);
    strokeWeight(random(5, 10));
    point(this.position.x, this.position.y);
  }

  fade() {
    this.opacity -= 1;
  }

  isOffScreen() {
    return (
      this.position.x < 0 ||
      this.position.x > width ||
      this.position.y < 0 ||
      this.position.y > height
    );
  }
}