anchor.diff:         (error "Los territorios deben estar conectados"))
        (unless (eq (owner origin) (owner destination))
          (error "Los territorios tienen que tener el mismo dueño"))
  -     (unless (> amount 0)
  +     (unless (plusp amount)
          (error "No se pueden mover 0 o menos ejércitos"))
        (unless (>= (movable-armies origin) amount)
          (error "No hay suficientes ejércitos"))
  
positive.code: 
  (defclass* game ()
    ((game-map nil r)
     (fsm nil)
     (players (make-hash-table :test 'equalp) r)
     (players-round nil)
     (turn-player nil)
     (pending-armies nil r)))
  
  (defmethod initialize-instance :after ((game game) &rest rest
                                                     &key game-map players)
  
negative.code:                     :initial-armies initial-armies)))
  
    (:method ((file stream))
     (let ((*read-eval* nil))
       (read-map (read file))))
  
    (:method ((path pathname))
  