fire.js

function Particle(x, y, color){
  this.pos = createVector(x + random(-10, 10), y + random(-10, 10));
  this.vel = createVector(floor(random(-1, 1))*noise(this.pos.x), -noise(this.pos.y)*7);
  this.alpha = 255;
  this.r = random(170, 255);
  this.g = random(10, 255);
  this.b = random(0, 100);
  
  this.update = function(){
    this.pos.add(this.vel);
    this.alpha -= 5;
  }
  
  this.show = function(){
    noStroke();
    fill(this.r, this.g, this.b, this.alpha);
    rect(this.pos.x, this.pos.y, 5, 5);
  }
  
  this.dead = function(){
    if(this.alpha < 0){
      return true;
    }else{
      return false;
    }
  }
}