anchor.diff:    void nullMainDirection() {
       if (!mainDirection.isZero) mainDirection = _zeroVector;
     }
  -  
  +
     /**
      * Set the main direction's x component to zero.
      */
     void nullMainDirectionX() {
       mainDirection *= _zeroOneVector;
     }
  -  
  +
     /**
      * Set the main direction's y component to zero.
      */
  
positive.code:       case Direction.RIGHT:
          mainDirection = rightDirection;
          break;
      }
    }
  
  
negative.code:    */
    void rotateDirectionsRadians(num radians) {
      mainDirection = mainDirection.rotate(radians);
      
      upDirection = upDirection.rotate(radians);
      downDirection = downDirection.rotate(radians);
      leftDirection = leftDirection.rotate(radians);
      rightDirection = rightDirection.rotate(radians);
      
      upLeftDirection = upLeftDirection.rotate(radians);
      upRightDirection = upRightDirection.rotate(radians);
      downLeftDirection = downLeftDirection.rotate(radians);
      downRightDirection = downRightDirection.rotate(radians);
    }
  
    /**
  