anchor.diff:  (defvar *space* (make-hash-table :test 'equal))
   (defparameter *chunk-width* 256)
   (defparameter *chunk-height* 256)
  +(defparameter *gravity-area-size* 4) ; 4 chunks to every direction from the chunk the ship is in → 11x11 chunks
   
   (defun generate-chunk (chunk-x chunk-y)
   	;; TODO: actually generate something
  
positive.code: 		(when (= (slot-value chunk 'references) 0)
  			(unload-chunk chunk-x chunk-y))))
  
  (defun enter-chunk (ship chunk-x chunk-y)
  	;; Mark that we use this chunk
  	(require-chunk chunk-x chunk-y)
  	(let ((chunk (get-chunk chunk-x chunk-y)))
  		;; Add ship to the list of ships
  		(setf (slot-value chunk 'ships) (cons ship (slot-value chunk 'ships)))))
  
negative.code: 		;; Remove ship from the list of ships
  		(setf (slot-value chunk 'ships) (remove ship (slot-value chunk 'ships))))
  	;; Mark that we no longer use this chunk
  	(unrequire-chunk chunk-x chunk-y)
  	;; Mark that we no longer use the gravity area either
  	(unrequire-gravity-area chunk-x chunk-y))
  
  (defun ships-in-chunk (chunk-x chunk-y)
  	(let ((chunk (get-chunk chunk-x chunk-y)))
  