anchor.diff:      (gl:with-pushed-matrix
         (p2dglu:translate2 position)
         (p2dglu:color4 color)
  -      (p2dglu:rotatez* orientation)
  -      (gl:scale 8 10 8)
  +      (p2dglu:rotatez* (- orientation (/ p2dm:+pi+ 2)))
  +      (gl:scale 7 10 7)
         (p2dglu:draw-triangle))))
   
   
positive.code: (defparameter +min-boid-distance-to-game-area-boundary+ 30)
  
  (defparameter +boid-perception-range+ 50)
  
  
  
negative.code: (defclass player (entity)
    ((orientation :initarg :orientation
                  :initform 0.0
                  :accessor player-orientation)
     (speed :initarg :speed
            :initform 30.0
            :accessor player-speed)
     (angular-speed :initarg :speed
                    :initform p2dm:+pi+
                    :accessor player-angular-speed)))
  
  (defun make-default-player ()
    (make-instance 'player
  