anchor.diff:    (format t "> forces-2-2~%")
     (format t "> forces-2-3~%")
     (format t "> forces-2-4~%")
  -  (format t "> forces-2-5~%"))
  +  (format t "> forces-2-5~%")
  +  (format t "> forces-2-6~%")
  +  (format t "> forces-2-7~%"))
  
positive.code:    (acceleration :initarg :acceleration :initform nil :accessor acceleration)
     (topspeed :initarg :topspeed :initform nil :accessor topspeed)
     (mass :initarg :mass :initform 1 :accessor mass)))
  
  
  (defclass liquid ()
  
negative.code: 
  (defparameter *movers* nil)
  (defparameter *liquids* nil)
  (defparameter *attractors* nil)
  (defparameter *wind* nil)
  (defparameter *gravity* nil)
  (defparameter *friction* nil)
  