diff --git a/biome.lisp b/biome.lisp
deleted file mode 100644
index fde3c3e..0000000
--- a/biome.lisp
+++ /dev/null
@@ -1,65 +0,0 @@
-;;;;
-;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
-;;;;
-;;;; Biomes are habitat types, that provide default functions for patches.
-;;;; This file defines the biome struct and the inbuilt biomes.
-;;;; 
-;;;; (c) 2018 Daniel Vedder, MIT license
-;;;;
-
-;; Biome struct and register
-
-(defstruct biome
-	(name "")
-	(ground "")
-	(occupants '()) ;an alist of possible occupants and their probabilities
-	(char #\.) ;default map display character
-	(col 'white)) ;default map display colour
-
-
-(let ((biome-list NIL))
-	(defun register-biome (symbol-name biome-object)
-		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
-
-	(defun available-biomes ()
-		(keys biome-list))
-
-	(defun get-biome (symbol-name)
-		(cassoc symbol-name biome-list)))
-
-(defmacro new-biome (name &body body)
-	`(register-biome ,name
-		 (make-biome ,@body)))
-
-
-;; Biome definitions
-
-(new-biome 'grassland
-	:name "grassland"
-	:ground "tall elephant grass"
-	:char #\; :col 'yellow
-	:occupants '((acacia 5) (boulder 1))) ;TODO
-
-(new-biome 'forest
-	:name "forest"
-	:ground "leaf litter and small shrubs"
-	:char #\. :col 'green
-	:occupants '((miombo 20) (acacia 10))) ;TODO
-
-(new-biome 'stream
-	:name "stream"
-	:ground "shallow flowing water"
-	:char #\~ :col 'blue
-	:occupants '()) ;TODO
-
-(new-biome 'swamp
-	:name "swamp"
-	:ground "short sedge grass growing on boggy black soil"
-	:char #\w :col 'green
-	:occupants '()) ;TODO
-
-(new-biome 'hill
-	:name "hill"
-	:ground "hard, stony soil"
-	:char #\m :col 'white
-	:occupants '((boulder 15))) ;TODO

diff --git a/biome.lisp b/biome.lisp
deleted file mode 100644
index fde3c3e..0000000
--- a/biome.lisp
+++ /dev/null
@@ -1,65 +0,0 @@
-;;;;
-;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
-;;;;
-;;;; Biomes are habitat types, that provide default functions for patches.
-;;;; This file defines the biome struct and the inbuilt biomes.
-;;;; 
-;;;; (c) 2018 Daniel Vedder, MIT license
-;;;;
-
-;; Biome struct and register
-
-(defstruct biome
-	(name "")
-	(ground "")
-	(occupants '()) ;an alist of possible occupants and their probabilities
-	(char #\.) ;default map display character
-	(col 'white)) ;default map display colour
-
-
-(let ((biome-list NIL))
-	(defun register-biome (symbol-name biome-object)
-		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
-
-	(defun available-biomes ()
-		(keys biome-list))
-
-	(defun get-biome (symbol-name)
-		(cassoc symbol-name biome-list)))
-
-(defmacro new-biome (name &body body)
-	`(register-biome ,name
-		 (make-biome ,@body)))
-
-
-;; Biome definitions
-
-(new-biome 'grassland
-	:name "grassland"
-	:ground "tall elephant grass"
-	:char #\; :col 'yellow
-	:occupants '((acacia 5) (boulder 1))) ;TODO
-
-(new-biome 'forest
-	:name "forest"
-	:ground "leaf litter and small shrubs"
-	:char #\. :col 'green
-	:occupants '((miombo 20) (acacia 10))) ;TODO
-
-(new-biome 'stream
-	:name "stream"
-	:ground "shallow flowing water"
-	:char #\~ :col 'blue
-	:occupants '()) ;TODO
-
-(new-biome 'swamp
-	:name "swamp"
-	:ground "short sedge grass growing on boggy black soil"
-	:char #\w :col 'green
-	:occupants '()) ;TODO
-
-(new-biome 'hill
-	:name "hill"
-	:ground "hard, stony soil"
-	:char #\m :col 'white
-	:occupants '((boulder 15))) ;TODO
diff --git a/biomes.lisp b/biomes.lisp
new file mode 100644
index 0000000..fde3c3e
--- /dev/null
+++ b/biomes.lisp
@@ -0,0 +1,65 @@
+;;;;
+;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
+;;;;
+;;;; Biomes are habitat types, that provide default functions for patches.
+;;;; This file defines the biome struct and the inbuilt biomes.
+;;;; 
+;;;; (c) 2018 Daniel Vedder, MIT license
+;;;;
+
+;; Biome struct and register
+
+(defstruct biome
+	(name "")
+	(ground "")
+	(occupants '()) ;an alist of possible occupants and their probabilities
+	(char #\.) ;default map display character
+	(col 'white)) ;default map display colour
+
+
+(let ((biome-list NIL))
+	(defun register-biome (symbol-name biome-object)
+		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
+
+	(defun available-biomes ()
+		(keys biome-list))
+
+	(defun get-biome (symbol-name)
+		(cassoc symbol-name biome-list)))
+
+(defmacro new-biome (name &body body)
+	`(register-biome ,name
+		 (make-biome ,@body)))
+
+
+;; Biome definitions
+
+(new-biome 'grassland
+	:name "grassland"
+	:ground "tall elephant grass"
+	:char #\; :col 'yellow
+	:occupants '((acacia 5) (boulder 1))) ;TODO
+
+(new-biome 'forest
+	:name "forest"
+	:ground "leaf litter and small shrubs"
+	:char #\. :col 'green
+	:occupants '((miombo 20) (acacia 10))) ;TODO
+
+(new-biome 'stream
+	:name "stream"
+	:ground "shallow flowing water"
+	:char #\~ :col 'blue
+	:occupants '()) ;TODO
+
+(new-biome 'swamp
+	:name "swamp"
+	:ground "short sedge grass growing on boggy black soil"
+	:char #\w :col 'green
+	:occupants '()) ;TODO
+
+(new-biome 'hill
+	:name "hill"
+	:ground "hard, stony soil"
+	:char #\m :col 'white
+	:occupants '((boulder 15))) ;TODO

diff --git a/biome.lisp b/biome.lisp
deleted file mode 100644
index fde3c3e..0000000
--- a/biome.lisp
+++ /dev/null
@@ -1,65 +0,0 @@
-;;;;
-;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
-;;;;
-;;;; Biomes are habitat types, that provide default functions for patches.
-;;;; This file defines the biome struct and the inbuilt biomes.
-;;;; 
-;;;; (c) 2018 Daniel Vedder, MIT license
-;;;;
-
-;; Biome struct and register
-
-(defstruct biome
-	(name "")
-	(ground "")
-	(occupants '()) ;an alist of possible occupants and their probabilities
-	(char #\.) ;default map display character
-	(col 'white)) ;default map display colour
-
-
-(let ((biome-list NIL))
-	(defun register-biome (symbol-name biome-object)
-		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
-
-	(defun available-biomes ()
-		(keys biome-list))
-
-	(defun get-biome (symbol-name)
-		(cassoc symbol-name biome-list)))
-
-(defmacro new-biome (name &body body)
-	`(register-biome ,name
-		 (make-biome ,@body)))
-
-
-;; Biome definitions
-
-(new-biome 'grassland
-	:name "grassland"
-	:ground "tall elephant grass"
-	:char #\; :col 'yellow
-	:occupants '((acacia 5) (boulder 1))) ;TODO
-
-(new-biome 'forest
-	:name "forest"
-	:ground "leaf litter and small shrubs"
-	:char #\. :col 'green
-	:occupants '((miombo 20) (acacia 10))) ;TODO
-
-(new-biome 'stream
-	:name "stream"
-	:ground "shallow flowing water"
-	:char #\~ :col 'blue
-	:occupants '()) ;TODO
-
-(new-biome 'swamp
-	:name "swamp"
-	:ground "short sedge grass growing on boggy black soil"
-	:char #\w :col 'green
-	:occupants '()) ;TODO
-
-(new-biome 'hill
-	:name "hill"
-	:ground "hard, stony soil"
-	:char #\m :col 'white
-	:occupants '((boulder 15))) ;TODO
diff --git a/biomes.lisp b/biomes.lisp
new file mode 100644
index 0000000..fde3c3e
--- /dev/null
+++ b/biomes.lisp
@@ -0,0 +1,65 @@
+;;;;
+;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
+;;;;
+;;;; Biomes are habitat types, that provide default functions for patches.
+;;;; This file defines the biome struct and the inbuilt biomes.
+;;;; 
+;;;; (c) 2018 Daniel Vedder, MIT license
+;;;;
+
+;; Biome struct and register
+
+(defstruct biome
+	(name "")
+	(ground "")
+	(occupants '()) ;an alist of possible occupants and their probabilities
+	(char #\.) ;default map display character
+	(col 'white)) ;default map display colour
+
+
+(let ((biome-list NIL))
+	(defun register-biome (symbol-name biome-object)
+		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
+
+	(defun available-biomes ()
+		(keys biome-list))
+
+	(defun get-biome (symbol-name)
+		(cassoc symbol-name biome-list)))
+
+(defmacro new-biome (name &body body)
+	`(register-biome ,name
+		 (make-biome ,@body)))
+
+
+;; Biome definitions
+
+(new-biome 'grassland
+	:name "grassland"
+	:ground "tall elephant grass"
+	:char #\; :col 'yellow
+	:occupants '((acacia 5) (boulder 1))) ;TODO
+
+(new-biome 'forest
+	:name "forest"
+	:ground "leaf litter and small shrubs"
+	:char #\. :col 'green
+	:occupants '((miombo 20) (acacia 10))) ;TODO
+
+(new-biome 'stream
+	:name "stream"
+	:ground "shallow flowing water"
+	:char #\~ :col 'blue
+	:occupants '()) ;TODO
+
+(new-biome 'swamp
+	:name "swamp"
+	:ground "short sedge grass growing on boggy black soil"
+	:char #\w :col 'green
+	:occupants '()) ;TODO
+
+(new-biome 'hill
+	:name "hill"
+	:ground "hard, stony soil"
+	:char #\m :col 'white
+	:occupants '((boulder 15))) ;TODO
diff --git a/terranostra.lisp b/terranostra.lisp
index 93c8e60..a4f8ed9 100644
--- a/terranostra.lisp
+++ b/terranostra.lisp
@@ -1,158 +1,23 @@
-;#!/usr/bin/clisp
 ;;;;
 ;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
 ;;;;
-;;;; This file defines patches and administrates the world object.
+;;;; This is the main program file.
 ;;;;
 ;;;; (c) 2018 Daniel Vedder, MIT license
 ;;;;
 
+
 (defvar *debugging* T)
 
 (load "util.lisp")
 (load "items.lisp")
 (load "biome.lisp")
 (load "animals.lisp")
+(load "world.lisp")
 
-(defvar *world* NIL)
-(defconstant *directions* '(N NE E SE S SW W NW))
-
-(defstruct patch
-	(pos '(0 0)) ;position
-	(biome NIL)
-	(items '())
-	(occupant NIL))
-
-
-(defun init-matrix (size)
-	"Create a square matrix of empty patches"
-	(debugging "~&Creating a ~S/~S matrix." size size)
-	(do ((y 0 (1+ y)) (world NIL) (row NIL NIL))
-		((= y size) world)
-		(dotimes (x size)
-			(setf row (append row (list (make-patch :pos (list x y))))))
-		(setf world (append world (list row)))))
-
-(defun coord (x y &optional (world *world*))
-	"Return the patch at the given coordinates or NIL if out of bounds"
-	(unless (or (< x 0) (< y 0) (> x (length world)) (> y (length world)))
-		(nth x (nth y world))))
-
-(defun distance (x1 y1 x2 y2)
-	"Find the distance between two sets of coordinates"
-	;;Ignores Pythagoras
-	(min (abs (- x1 x2)) (abs (- y1 y2))))
-
-(defun closest-coords (here coord-list)
-	"Find the closest position to 'here' from a list of coordinates"
-	(do* ((clist coord-list (cdr clist)) (c (car clist) (car clist))
-			 (dist (when c (distance (first here) (second here)
-							   (first c) (second c)))
-				 (when c (distance (first here) (second here)
-							 (first c) (second c))))
-			 (mindist dist) (closest c))
-		((null clist) closest)
-		(when (< dist mindist)
-			(setf mindist dist closest c))))
-
-(defun opposite-dir (dir)
-	"Return the direction opposite the input"
-	(let ((pos (position dir *directions*)))
-		(when pos (nth (rem (+ 4 pos) 8) *directions*))))
-
-(defun next-dir (dir &optional (cw T))
-	"Get the neighbouring direction (clockwise or anticlockwise)"
-	(let ((pos (position dir *directions*))
-			 (diff (if cw 1 -1)))
-		(when pos (nth (rem (+ diff pos 8) 8) *directions*))))
-
-(defun dir2patch (herex herey therex therey)
-	"Calculate the direction to a patch"
-	(cond ((> herex therex)
-			  (cond ((> herey therey) 'NW)					 
-				  ((< herey therey) 'SW)
-				  (T 'W)))
-		((< herex therex)
-			(cond ((> herey therey) 'NE)
-				((< herey therey) 'SE)
-				(T 'E)))
-		(T (cond ((> herey therey) 'N)
-			   ((< herey therey) 'S)
-			   (T NIL)))))
-
-(defun coordsindir (x y dir)
-	"Return the coordinates in the given direction"
-	(cond ((eq dir 'N) (list x (1- y)))
-		((eq dir 'NE) (list (1+ x) (1- y)))
-		((eq dir 'E) (list (1+ x) y))
-		((eq dir 'SE) (list (1+ x) (1+ y)))
-		((eq dir 'S) (list x (1+ y)))
-		((eq dir 'SW) (list (1- x) (1+ y)))
-		((eq dir 'W) (list (1- x) y))
-		((eq dir 'NW) (list (1- x) (1- y)))
-		((null dir) (list x y))
-		(T (error "~&Invalid direction ~S"))))
-
-(defun patchindir (x y dir &optional (world *world*))
-	"Return the patch in the given direction"
-	(let* ((coords (coordsindir x y dir))
-			  (nextx (first coords)) (nexty (second coords)))
-		(coord nextx nexty world)))
-
-(defun neighbour (p dir &optional (world *world*))
-	"Return the neighbouring patch in this direction"
-	(patchindir (first (patch-pos p)) (second (patch-pos p)) dir world))
-
-(defun save-topography (file-name &optional (world *world*))
-	"Save the world topography as a text file"
-	(debugging "~&Saving world to file ~A" file-name) ;debug
-	(with-open-file (tf file-name :direction :output)
-		(dolist (row world)
-			(format (if file-name tf T) "~&~A~%"
-				(string-from-list
-					(mapcar #'(lambda (p) (biome-char (patch-biome p))) row)
-					" ")))))
-	
-(defun generate-biomes (size-factor &optional (world *world*))
-	;;XXX The maps this produces don't look as expected, but for
-	;; current purposes they are good enough
-	(debugging "~&Generating biomes") ;debug
-	(let* ((world-size (length world)) (seeds NIL)
-			  (nseeds (round (/ world-size size-factor)))
-			  (biomes (remove-first-if
-						  #'(lambda (e) (eq e 'stream))
-						  (available-biomes))))
-		;;Initialize a set of biome 'seed' coordinates
-		(dotimes (n nseeds)
-			(setf seeds
-				(cons (list (random world-size)
-						  (random world-size)
-						  (random-elt biomes))
-					seeds)))
-		(debugging "~&~S" seeds)
-		;;For each patch, calculate the closest seed and set to that biome
-		(dotimes (x world-size)
-			(dotimes (y world-size)
-				(let ((b (third (closest-coords (list x y) seeds))))
-					(setf (patch-biome (coord x y world))
-						(get-biome b)))))))
-	
-(defun generate-stream (x0 y0 &optional (world *world*))
-	(debugging "~&Generating a stream, starting at ~S/~S" x0 y0) ;debug
-	(do* ((dir (random-elt *directions*)
-			  (if (chancep 60) dir (next-dir dir (random-elt '(T NIL)))))
-			 (patch (coord x0 y0 world) (neighbour patch dir world)))
-		((or (null patch) (eq (patch-biome patch) (get-biome 'stream))))
-		(setf (patch-biome patch) (get-biome 'stream))))
-
-(defun create-world (size name &optional (world *world*))
-	(setf world NIL)
-	(setf world (init-matrix size))
-	;;XXX magic numbers
-	(generate-biomes 20 world)
-	(dotimes (s (round (/ (expt size 2) 500)))
-		(generate-stream (random size) (random size) world))
-	(save-topography name world))
 
 ;; Initialize the random state (which would otherwise not be very random...)
 (setf *random-state* (make-random-state t))
+
+(create-world 100 "test.world")
+

diff --git a/biome.lisp b/biome.lisp
deleted file mode 100644
index fde3c3e..0000000
--- a/biome.lisp
+++ /dev/null
@@ -1,65 +0,0 @@
-;;;;
-;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
-;;;;
-;;;; Biomes are habitat types, that provide default functions for patches.
-;;;; This file defines the biome struct and the inbuilt biomes.
-;;;; 
-;;;; (c) 2018 Daniel Vedder, MIT license
-;;;;
-
-;; Biome struct and register
-
-(defstruct biome
-	(name "")
-	(ground "")
-	(occupants '()) ;an alist of possible occupants and their probabilities
-	(char #\.) ;default map display character
-	(col 'white)) ;default map display colour
-
-
-(let ((biome-list NIL))
-	(defun register-biome (symbol-name biome-object)
-		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
-
-	(defun available-biomes ()
-		(keys biome-list))
-
-	(defun get-biome (symbol-name)
-		(cassoc symbol-name biome-list)))
-
-(defmacro new-biome (name &body body)
-	`(register-biome ,name
-		 (make-biome ,@body)))
-
-
-;; Biome definitions
-
-(new-biome 'grassland
-	:name "grassland"
-	:ground "tall elephant grass"
-	:char #\; :col 'yellow
-	:occupants '((acacia 5) (boulder 1))) ;TODO
-
-(new-biome 'forest
-	:name "forest"
-	:ground "leaf litter and small shrubs"
-	:char #\. :col 'green
-	:occupants '((miombo 20) (acacia 10))) ;TODO
-
-(new-biome 'stream
-	:name "stream"
-	:ground "shallow flowing water"
-	:char #\~ :col 'blue
-	:occupants '()) ;TODO
-
-(new-biome 'swamp
-	:name "swamp"
-	:ground "short sedge grass growing on boggy black soil"
-	:char #\w :col 'green
-	:occupants '()) ;TODO
-
-(new-biome 'hill
-	:name "hill"
-	:ground "hard, stony soil"
-	:char #\m :col 'white
-	:occupants '((boulder 15))) ;TODO
diff --git a/biomes.lisp b/biomes.lisp
new file mode 100644
index 0000000..fde3c3e
--- /dev/null
+++ b/biomes.lisp
@@ -0,0 +1,65 @@
+;;;;
+;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
+;;;;
+;;;; Biomes are habitat types, that provide default functions for patches.
+;;;; This file defines the biome struct and the inbuilt biomes.
+;;;; 
+;;;; (c) 2018 Daniel Vedder, MIT license
+;;;;
+
+;; Biome struct and register
+
+(defstruct biome
+	(name "")
+	(ground "")
+	(occupants '()) ;an alist of possible occupants and their probabilities
+	(char #\.) ;default map display character
+	(col 'white)) ;default map display colour
+
+
+(let ((biome-list NIL))
+	(defun register-biome (symbol-name biome-object)
+		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
+
+	(defun available-biomes ()
+		(keys biome-list))
+
+	(defun get-biome (symbol-name)
+		(cassoc symbol-name biome-list)))
+
+(defmacro new-biome (name &body body)
+	`(register-biome ,name
+		 (make-biome ,@body)))
+
+
+;; Biome definitions
+
+(new-biome 'grassland
+	:name "grassland"
+	:ground "tall elephant grass"
+	:char #\; :col 'yellow
+	:occupants '((acacia 5) (boulder 1))) ;TODO
+
+(new-biome 'forest
+	:name "forest"
+	:ground "leaf litter and small shrubs"
+	:char #\. :col 'green
+	:occupants '((miombo 20) (acacia 10))) ;TODO
+
+(new-biome 'stream
+	:name "stream"
+	:ground "shallow flowing water"
+	:char #\~ :col 'blue
+	:occupants '()) ;TODO
+
+(new-biome 'swamp
+	:name "swamp"
+	:ground "short sedge grass growing on boggy black soil"
+	:char #\w :col 'green
+	:occupants '()) ;TODO
+
+(new-biome 'hill
+	:name "hill"
+	:ground "hard, stony soil"
+	:char #\m :col 'white
+	:occupants '((boulder 15))) ;TODO
diff --git a/terranostra.lisp b/terranostra.lisp
index 93c8e60..a4f8ed9 100644
--- a/terranostra.lisp
+++ b/terranostra.lisp
@@ -1,158 +1,23 @@
-;#!/usr/bin/clisp
 ;;;;
 ;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
 ;;;;
-;;;; This file defines patches and administrates the world object.
+;;;; This is the main program file.
 ;;;;
 ;;;; (c) 2018 Daniel Vedder, MIT license
 ;;;;
 
+
 (defvar *debugging* T)
 
 (load "util.lisp")
 (load "items.lisp")
 (load "biome.lisp")
 (load "animals.lisp")
+(load "world.lisp")
 
-(defvar *world* NIL)
-(defconstant *directions* '(N NE E SE S SW W NW))
-
-(defstruct patch
-	(pos '(0 0)) ;position
-	(biome NIL)
-	(items '())
-	(occupant NIL))
-
-
-(defun init-matrix (size)
-	"Create a square matrix of empty patches"
-	(debugging "~&Creating a ~S/~S matrix." size size)
-	(do ((y 0 (1+ y)) (world NIL) (row NIL NIL))
-		((= y size) world)
-		(dotimes (x size)
-			(setf row (append row (list (make-patch :pos (list x y))))))
-		(setf world (append world (list row)))))
-
-(defun coord (x y &optional (world *world*))
-	"Return the patch at the given coordinates or NIL if out of bounds"
-	(unless (or (< x 0) (< y 0) (> x (length world)) (> y (length world)))
-		(nth x (nth y world))))
-
-(defun distance (x1 y1 x2 y2)
-	"Find the distance between two sets of coordinates"
-	;;Ignores Pythagoras
-	(min (abs (- x1 x2)) (abs (- y1 y2))))
-
-(defun closest-coords (here coord-list)
-	"Find the closest position to 'here' from a list of coordinates"
-	(do* ((clist coord-list (cdr clist)) (c (car clist) (car clist))
-			 (dist (when c (distance (first here) (second here)
-							   (first c) (second c)))
-				 (when c (distance (first here) (second here)
-							 (first c) (second c))))
-			 (mindist dist) (closest c))
-		((null clist) closest)
-		(when (< dist mindist)
-			(setf mindist dist closest c))))
-
-(defun opposite-dir (dir)
-	"Return the direction opposite the input"
-	(let ((pos (position dir *directions*)))
-		(when pos (nth (rem (+ 4 pos) 8) *directions*))))
-
-(defun next-dir (dir &optional (cw T))
-	"Get the neighbouring direction (clockwise or anticlockwise)"
-	(let ((pos (position dir *directions*))
-			 (diff (if cw 1 -1)))
-		(when pos (nth (rem (+ diff pos 8) 8) *directions*))))
-
-(defun dir2patch (herex herey therex therey)
-	"Calculate the direction to a patch"
-	(cond ((> herex therex)
-			  (cond ((> herey therey) 'NW)					 
-				  ((< herey therey) 'SW)
-				  (T 'W)))
-		((< herex therex)
-			(cond ((> herey therey) 'NE)
-				((< herey therey) 'SE)
-				(T 'E)))
-		(T (cond ((> herey therey) 'N)
-			   ((< herey therey) 'S)
-			   (T NIL)))))
-
-(defun coordsindir (x y dir)
-	"Return the coordinates in the given direction"
-	(cond ((eq dir 'N) (list x (1- y)))
-		((eq dir 'NE) (list (1+ x) (1- y)))
-		((eq dir 'E) (list (1+ x) y))
-		((eq dir 'SE) (list (1+ x) (1+ y)))
-		((eq dir 'S) (list x (1+ y)))
-		((eq dir 'SW) (list (1- x) (1+ y)))
-		((eq dir 'W) (list (1- x) y))
-		((eq dir 'NW) (list (1- x) (1- y)))
-		((null dir) (list x y))
-		(T (error "~&Invalid direction ~S"))))
-
-(defun patchindir (x y dir &optional (world *world*))
-	"Return the patch in the given direction"
-	(let* ((coords (coordsindir x y dir))
-			  (nextx (first coords)) (nexty (second coords)))
-		(coord nextx nexty world)))
-
-(defun neighbour (p dir &optional (world *world*))
-	"Return the neighbouring patch in this direction"
-	(patchindir (first (patch-pos p)) (second (patch-pos p)) dir world))
-
-(defun save-topography (file-name &optional (world *world*))
-	"Save the world topography as a text file"
-	(debugging "~&Saving world to file ~A" file-name) ;debug
-	(with-open-file (tf file-name :direction :output)
-		(dolist (row world)
-			(format (if file-name tf T) "~&~A~%"
-				(string-from-list
-					(mapcar #'(lambda (p) (biome-char (patch-biome p))) row)
-					" ")))))
-	
-(defun generate-biomes (size-factor &optional (world *world*))
-	;;XXX The maps this produces don't look as expected, but for
-	;; current purposes they are good enough
-	(debugging "~&Generating biomes") ;debug
-	(let* ((world-size (length world)) (seeds NIL)
-			  (nseeds (round (/ world-size size-factor)))
-			  (biomes (remove-first-if
-						  #'(lambda (e) (eq e 'stream))
-						  (available-biomes))))
-		;;Initialize a set of biome 'seed' coordinates
-		(dotimes (n nseeds)
-			(setf seeds
-				(cons (list (random world-size)
-						  (random world-size)
-						  (random-elt biomes))
-					seeds)))
-		(debugging "~&~S" seeds)
-		;;For each patch, calculate the closest seed and set to that biome
-		(dotimes (x world-size)
-			(dotimes (y world-size)
-				(let ((b (third (closest-coords (list x y) seeds))))
-					(setf (patch-biome (coord x y world))
-						(get-biome b)))))))
-	
-(defun generate-stream (x0 y0 &optional (world *world*))
-	(debugging "~&Generating a stream, starting at ~S/~S" x0 y0) ;debug
-	(do* ((dir (random-elt *directions*)
-			  (if (chancep 60) dir (next-dir dir (random-elt '(T NIL)))))
-			 (patch (coord x0 y0 world) (neighbour patch dir world)))
-		((or (null patch) (eq (patch-biome patch) (get-biome 'stream))))
-		(setf (patch-biome patch) (get-biome 'stream))))
-
-(defun create-world (size name &optional (world *world*))
-	(setf world NIL)
-	(setf world (init-matrix size))
-	;;XXX magic numbers
-	(generate-biomes 20 world)
-	(dotimes (s (round (/ (expt size 2) 500)))
-		(generate-stream (random size) (random size) world))
-	(save-topography name world))
 
 ;; Initialize the random state (which would otherwise not be very random...)
 (setf *random-state* (make-random-state t))
+
+(create-world 100 "test.world")
+
diff --git a/world.lisp b/world.lisp
new file mode 100644
index 0000000..64275ee
--- /dev/null
+++ b/world.lisp
@@ -0,0 +1,152 @@
+;;;;
+;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
+;;;;
+;;;; This file defines patches and administrates the world object.
+;;;;
+;;;; (c) 2018 Daniel Vedder, MIT license
+;;;;
+
+(defvar *world* NIL)
+(defconstant *directions* '(N NE E SE S SW W NW))
+
+(defstruct patch
+	(pos '(0 0)) ;position
+	(biome NIL)
+	(items '())
+	(occupant NIL))
+
+;; MATRIX FUNCTIONS
+
+(defun init-matrix (size)
+	"Create a square matrix of empty patches"
+	;;TODO change this to arrays for performance
+	(debugging "~&Creating a ~S/~S matrix." size size)
+	(do ((y 0 (1+ y)) (world NIL) (row NIL NIL))
+		((= y size) world)
+		(dotimes (x size)
+			(setf row (append row (list (make-patch :pos (list x y))))))
+		(setf world (append world (list row)))))
+
+(defun coord (x y &optional (world *world*))
+	"Return the patch at the given coordinates or NIL if out of bounds"
+	(unless (or (< x 0) (< y 0) (> x (length world)) (> y (length world)))
+		(nth x (nth y world))))
+
+(defun distance (x1 y1 x2 y2)
+	"Find the distance between two sets of coordinates"
+	;;Ignores Pythagoras
+	(min (abs (- x1 x2)) (abs (- y1 y2))))
+
+(defun closest-coords (here coord-list)
+	"Find the closest position to 'here' from a list of coordinates"
+	(do* ((clist coord-list (cdr clist)) (c (car clist) (car clist))
+			 (dist (when c (distance (first here) (second here)
+							   (first c) (second c)))
+				 (when c (distance (first here) (second here)
+							 (first c) (second c))))
+			 (mindist dist) (closest c))
+		((null clist) closest)
+		(when (< dist mindist)
+			(setf mindist dist closest c))))
+
+(defun opposite-dir (dir)
+	"Return the direction opposite the input"
+	(let ((pos (position dir *directions*)))
+		(when pos (nth (rem (+ 4 pos) 8) *directions*))))
+
+(defun next-dir (dir &optional (cw T))
+	"Get the neighbouring direction (clockwise or anticlockwise)"
+	(let ((pos (position dir *directions*))
+			 (diff (if cw 1 -1)))
+		(when pos (nth (rem (+ diff pos 8) 8) *directions*))))
+
+(defun dir2patch (herex herey therex therey)
+	"Calculate the direction to a patch"
+	(cond ((> herex therex)
+			  (cond ((> herey therey) 'NW)					 
+				  ((< herey therey) 'SW)
+				  (T 'W)))
+		((< herex therex)
+			(cond ((> herey therey) 'NE)
+				((< herey therey) 'SE)
+				(T 'E)))
+		(T (cond ((> herey therey) 'N)
+			   ((< herey therey) 'S)
+			   (T NIL)))))
+
+(defun coordsindir (x y dir)
+	"Return the coordinates in the given direction"
+	(cond ((eq dir 'N) (list x (1- y)))
+		((eq dir 'NE) (list (1+ x) (1- y)))
+		((eq dir 'E) (list (1+ x) y))
+		((eq dir 'SE) (list (1+ x) (1+ y)))
+		((eq dir 'S) (list x (1+ y)))
+		((eq dir 'SW) (list (1- x) (1+ y)))
+		((eq dir 'W) (list (1- x) y))
+		((eq dir 'NW) (list (1- x) (1- y)))
+		((null dir) (list x y))
+		(T (error "~&Invalid direction ~S"))))
+
+(defun patchindir (x y dir &optional (world *world*))
+	"Return the patch in the given direction"
+	(let* ((coords (coordsindir x y dir))
+			  (nextx (first coords)) (nexty (second coords)))
+		(coord nextx nexty world)))
+
+(defun neighbour (p dir &optional (world *world*))
+	"Return the neighbouring patch in this direction"
+	(patchindir (first (patch-pos p)) (second (patch-pos p)) dir world))
+
+
+;; TOPOGRAPHY FUNCTIONS
+
+(defun save-topography (file-name &optional (world *world*))
+	"Save the world topography as a text file"
+	(debugging "~&Saving world to file ~A" file-name) ;debug
+	(with-open-file (tf file-name :direction :output)
+		(dolist (row world)
+			(format (if file-name tf T) "~&~A~%"
+				(string-from-list
+					(mapcar #'(lambda (p) (biome-char (patch-biome p))) row)
+					" ")))))
+	
+(defun generate-biomes (size-factor &optional (world *world*))
+	;;XXX The maps this produces don't look as expected, but for
+	;; current purposes they are good enough
+	(debugging "~&Generating biomes") ;debug
+	(let* ((world-size (length world)) (seeds NIL)
+			  (nseeds (round (/ world-size size-factor)))
+			  (biomes (remove-first-if
+						  #'(lambda (e) (eq e 'stream))
+						  (available-biomes))))
+		;;Initialize a set of biome 'seed' coordinates
+		(dotimes (n nseeds)
+			(setf seeds
+				(cons (list (random world-size)
+						  (random world-size)
+						  (random-elt biomes))
+					seeds)))
+		(debugging "~&~S" seeds)
+		;;For each patch, calculate the closest seed and set to that biome
+		(dotimes (x world-size)
+			(dotimes (y world-size)
+				(let ((b (third (closest-coords (list x y) seeds))))
+					(setf (patch-biome (coord x y world))
+						(get-biome b)))))))
+	
+(defun generate-stream (x0 y0 &optional (world *world*))
+	(debugging "~&Generating a stream, starting at ~S/~S" x0 y0) ;debug
+	(do* ((dir (random-elt *directions*)
+			  (if (chancep 60) dir (next-dir dir (random-elt '(T NIL)))))
+			 (patch (coord x0 y0 world) (neighbour patch dir world)))
+		((or (null patch) (eq (patch-biome patch) (get-biome 'stream))))
+		(setf (patch-biome patch) (get-biome 'stream))))
+
+(defun create-world (size &optional name (world *world*))
+	(setf world NIL)
+	(setf world (init-matrix size))
+	;;XXX magic numbers
+	(generate-biomes 20 world)
+	(dotimes (s (round (/ (expt size 2) 500)))
+		(generate-stream (random size) (random size) world))
+	(when name (save-topography name world)))