code: function() {
          var lastEvent = this.lastMouseEvent;
  
          // Tell all buttons they're no longer held down
          var buttonsDown = this._buttonDown;
          for (var button in buttonsDown) {
              if (buttonsDown[button] === true) {
                  lastEvent.mouseButton = +button; // convert button propertyString to number!
                  lastEvent.eventName = "MouseUp";
                  this.triggerMouse("MouseUp", lastEvent);
              }
          }
  
          return this;
      }
docs: @
  #.resetButtonDown
  @comp MouseState
  @kind Method
  
  @sign public this .resetButtonDown()
  
  Reset all currently pressed buttons. Triggers appropriate "MouseUp" events.
  
  This method is called internally, but may be useful when running Crafty in headless mode.
  
  @see .isButtonDown
  @see Crafty.mouseButtons