docs: function (evt) {
      var threshold = 30;
      if (!this.pressed) {
        this.pressed = true;
        this.emit('touchdown');
        var self = this;
        this.interval = setInterval(function() {
          var delta = performance.now() - self.lastTime;
          if (delta > threshold) {
            self.pressed = false;
            self.lastTime = 0;
            self.emit('touchup');
            clearInterval(self.interval);
          }
        }, threshold);
      }
      this.lastTime = performance.now();
    }