const num_drops = 500;

​

let wind = 0;

let wind_off = 0;

​

function setup() {

  createCanvas(1920, 1080);

  for (let i=0; i<num_drops; i++) {

    drops.push(new Drop());

  }

  stroke(255);

}

​

function draw() {

  background(35);

  for (let i=0; i<num_drops; i++) {

    drops[i].draw();

    drops[i].update();

  }

  wind = noise(wind_off);

  wind_off += 0.005;

}

​

class Drop {

  constructor() {

    this.x = random(width);

    this.y = random(0,-height);

    this.grav = 0.1;

    this.z = random(1,20);

    this.len = map(this.z,1,20,5,30);

    this.vely = map(this.z,1,20,1,20);

    this.stroke = map(this.z,1,20,1,3);

    this.velx = 0;

  }

  update() {

    this.y += this.vely;

    this.vely += this.grav;

    this.x += this.velx;

    if (this.y > height) {

      this.y = random(0,-height); 

      this.vely = map(this.z,1,20,1,20);

    }

    if (this.x > width) this.x=0;

    if (this.x < 0) this.x=width;

    let drop_wind = map(wind,0,1,-20,20);

    this.velx = wind*drop_wind;

  }

  draw() {

    strokeWeight(this.stroke);

    line(this.x-this.velx*3,this.y,this.x, this.y+this.len);

  }

}

​

function mousePressed() {

  let fs = fullscreen();

  fullscreen(!fs);

}