docs: function Touch (game) {
    if (!(this instanceof Touch)) return new Touch(game)
    this.game = game || {}
    this.el = game.el || game.canvas || game.renderer.canvas || document
    this.left = this.el.scrollLeft + this.el.offsetLeft +
      (this.el.offsetParent ? this.el.offsetParent.offsetLeft : 0)
    this.top = this.el.scrollTop + this.el.offsetTop +
      (this.el.offsetParent ? this.el.offsetParent.offsetTop : 0)
    this.width = this.el.clientWidth
    this.height = this.el.clientHeight
    this.down = {}
    this.initialize()
  }