anchor.diff:    (let ((s (format nil "fps: ~,2f" (sdl:average-fps))))
       (set-caption s s)))
   
  +(defmethod update :after ((object mobile-object))
  +  (with-slots (offset veloc) object
  +    (cond ((< (x offset) 0)
  +           (setf veloc (complex (abs (x veloc)) (y veloc))))
  +          ((>= (x offset) (x (size (game-view *game*))))
  +           (setf veloc (complex (- (abs (x veloc))) (y veloc)))))
  +    (cond ((< (y offset) 0)
  +           (setf veloc (complex (x veloc) (abs (y veloc)))))
  +          ((>= (y offset) (y (size (game-view *game*))))
  +           (setf veloc (complex (x veloc) (- (abs (y veloc)))))))))
  +
   ;; For interactive use:
  -(defun mobile-test ()
  -  (let ((*game* (make-instance 'mobile-game)))
  +(defun mobile-test (&optional (n 5000))
  +  (let ((*game* (make-instance 'mobile-game :test-size n)))
       (main :exit-when-done nil)))
   
   ;; For non-interactive use:
  -(defvar *game* (make-instance 'mobile-game))+(defvar *game* (make-instance 'mobile-game :test-size 5000))
  
positive.code: 
  (in-package :blackthorn-stress-test)
  
  (defclass mobile-game (game) ())
  
  (defclass mobile-object (sprite mobile) ())
  
  
negative.code:         (size #c(800 600))
          (texture-pathname
           (merge-pathnames "disp/texture.png" *resource-directory-pathname*)))
      (loop for i from 0 to (test-size game)
         do (make-instance
             'mobile-object :parent root
             :offset (complex (random (x size)) (random (y size)))
             :veloc (complex (- (random 1.0) 0.5) (- (random 1.0) 0.5))
             :image (make-instance 'image :name 'tex
                                   :source texture-pathname)))
      (let ((keys (make-instance 'actor :parent root)))
        (define-event-handlers (event) keys
          (any-key t
  