diff --git a/lisp/atlantis.lisp b/lisp/atlantis.lisp
index 083b01f..f0d1770 100644
--- a/lisp/atlantis.lisp
+++ b/lisp/atlantis.lisp
@@ -17,8 +17,11 @@
 (load "ui.lisp")
 
 
+(defvar *debugging* NIL)
+
 (defun development ()
 	"A method to easily test whatever feature I am currently developing"
+	(setf *debugging* T)
 	(load-file "../ATL/lisp-test.atl")
 	(let ((player (make-player :name "Bilbo"
 					  :race (get-game-object 'race "Hobbit")
@@ -34,12 +37,13 @@
 
 (defun start-server ()
 	"Start a new game on a server"
+	;; TODO Doesn't actually start a server yet
 	(format t "~&What world file do you want to load?")
 	(input-string world-file) 
 	(format t "~&What port should the game run on?")
 	(while (not (numberp (input port)))
 		(format t "~&Not a number: ~A. Please reenter:" port))
-	(format t "~&Loading file ~S on port ~A" world-file port)
+	(debugging "~&Loading file ~S on port ~A" world-file port)
 	(load-file world-file))
 
 (defun join-game ()
@@ -56,7 +60,7 @@
 	;(setf (cassoc port *server-address*) server-port)
 	(format t "~&What is your player name?")
 	(input-string name)
-	(format t "~&Joining game on ~A:~A as ~A" server-ip server-port name)
+	(debugging "~&Joining game on ~A:~A as ~A" server-ip server-port name)
 	(play-game name))
 
 
@@ -80,7 +84,7 @@
 		(2 (start-menu))))
 
 (defun print-version ()
-	(format t "~&Lisp Atlantis ~A.~A.~A"
+	(format t "~&Atlantis ~A.~A.~A"
 		(first ATLANTIS-VERSION)
 		(second ATLANTIS-VERSION)
 		(third ATLANTIS-VERSION))
@@ -114,32 +118,38 @@
 
 (defun print-help ()
 	(print-version)
-	(format t "~&~%Commandline options:")
-	(let ((tab (string #\Tab)))
-		(format t "~&-v --version~AShow the version number and exit" tab)
-		(format t "~&-h --help~AShow this help text and exit" tab)
-		(format t "~&--license~AShow the license text" tab)
-		(format t "~&--server <port>~AStart a server on <port> (requires --world)" tab)
-		(format t "~&--world <world-file>~AThe ATL file to load (requires --server)" tab)
-		(format t "~&--client <ip>:<port>~AConnect to the game server at <ip>:<port>" tab)))
+	(setf help-text "
+Commandline options:
+-v --version          Show the version number and exit
+-h --help             Show this help text and exit
+--license             Show the license text
+--debugging           Switch on debug mode
+--single-player       Start a single-player game
+--server <port>       Start a server on <port> (requires --world)
+--world <world-file>  The ATL file to load (requires --server)
+--client <ip>:<port>  Connect to the game server at <ip>:<port>")
+	(format t "~A" help-text))
 
 (defun parse-commandline-args ()
 	;; TODO clean this up? (should give error message with unknown params)
-	(when (or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
+	(cond ((or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
 			  (print-version) (quit))
-	(when (or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
-		(print-help) (quit))
-	(when (cmd-parameter "--license" T)
-		(dolist (line (load-text-file "../LICENSE"))
-			(unless (null line) (format t "~%~A" line)))
-		(quit))
+		((or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
+			(print-help) (quit))
+		((cmd-parameter "--license" T)
+			(dolist (line (load-text-file "../LICENSE"))
+				(unless (null line) (format t "~%~A" line)))
+			(quit))
+		((cmd-parameter "--debugging")
+			(setf *debugging* T))
+		((cmd-parameter "--single-player" T)
+			(single-player)))
 	(let ((server (cmd-parameter "--server"))
 			 (world-file (cmd-parameter "--world"))
 			 (client (cmd-parameter "--client")))
 		(unless (or server world-file client)
 			(format t "~&Invalid commandline parameter!") (quit))
-		;; TODO change OR to AND, change function calls
-		(if (or world-file server)
+		(if (and world-file server)
 			(load-file world-file)
 			(join-game))))
 

diff --git a/lisp/atlantis.lisp b/lisp/atlantis.lisp
index 083b01f..f0d1770 100644
--- a/lisp/atlantis.lisp
+++ b/lisp/atlantis.lisp
@@ -17,8 +17,11 @@
 (load "ui.lisp")
 
 
+(defvar *debugging* NIL)
+
 (defun development ()
 	"A method to easily test whatever feature I am currently developing"
+	(setf *debugging* T)
 	(load-file "../ATL/lisp-test.atl")
 	(let ((player (make-player :name "Bilbo"
 					  :race (get-game-object 'race "Hobbit")
@@ -34,12 +37,13 @@
 
 (defun start-server ()
 	"Start a new game on a server"
+	;; TODO Doesn't actually start a server yet
 	(format t "~&What world file do you want to load?")
 	(input-string world-file) 
 	(format t "~&What port should the game run on?")
 	(while (not (numberp (input port)))
 		(format t "~&Not a number: ~A. Please reenter:" port))
-	(format t "~&Loading file ~S on port ~A" world-file port)
+	(debugging "~&Loading file ~S on port ~A" world-file port)
 	(load-file world-file))
 
 (defun join-game ()
@@ -56,7 +60,7 @@
 	;(setf (cassoc port *server-address*) server-port)
 	(format t "~&What is your player name?")
 	(input-string name)
-	(format t "~&Joining game on ~A:~A as ~A" server-ip server-port name)
+	(debugging "~&Joining game on ~A:~A as ~A" server-ip server-port name)
 	(play-game name))
 
 
@@ -80,7 +84,7 @@
 		(2 (start-menu))))
 
 (defun print-version ()
-	(format t "~&Lisp Atlantis ~A.~A.~A"
+	(format t "~&Atlantis ~A.~A.~A"
 		(first ATLANTIS-VERSION)
 		(second ATLANTIS-VERSION)
 		(third ATLANTIS-VERSION))
@@ -114,32 +118,38 @@
 
 (defun print-help ()
 	(print-version)
-	(format t "~&~%Commandline options:")
-	(let ((tab (string #\Tab)))
-		(format t "~&-v --version~AShow the version number and exit" tab)
-		(format t "~&-h --help~AShow this help text and exit" tab)
-		(format t "~&--license~AShow the license text" tab)
-		(format t "~&--server <port>~AStart a server on <port> (requires --world)" tab)
-		(format t "~&--world <world-file>~AThe ATL file to load (requires --server)" tab)
-		(format t "~&--client <ip>:<port>~AConnect to the game server at <ip>:<port>" tab)))
+	(setf help-text "
+Commandline options:
+-v --version          Show the version number and exit
+-h --help             Show this help text and exit
+--license             Show the license text
+--debugging           Switch on debug mode
+--single-player       Start a single-player game
+--server <port>       Start a server on <port> (requires --world)
+--world <world-file>  The ATL file to load (requires --server)
+--client <ip>:<port>  Connect to the game server at <ip>:<port>")
+	(format t "~A" help-text))
 
 (defun parse-commandline-args ()
 	;; TODO clean this up? (should give error message with unknown params)
-	(when (or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
+	(cond ((or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
 			  (print-version) (quit))
-	(when (or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
-		(print-help) (quit))
-	(when (cmd-parameter "--license" T)
-		(dolist (line (load-text-file "../LICENSE"))
-			(unless (null line) (format t "~%~A" line)))
-		(quit))
+		((or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
+			(print-help) (quit))
+		((cmd-parameter "--license" T)
+			(dolist (line (load-text-file "../LICENSE"))
+				(unless (null line) (format t "~%~A" line)))
+			(quit))
+		((cmd-parameter "--debugging")
+			(setf *debugging* T))
+		((cmd-parameter "--single-player" T)
+			(single-player)))
 	(let ((server (cmd-parameter "--server"))
 			 (world-file (cmd-parameter "--world"))
 			 (client (cmd-parameter "--client")))
 		(unless (or server world-file client)
 			(format t "~&Invalid commandline parameter!") (quit))
-		;; TODO change OR to AND, change function calls
-		(if (or world-file server)
+		(if (and world-file server)
 			(load-file world-file)
 			(join-game))))
 
diff --git a/lisp/game-objects.lisp b/lisp/game-objects.lisp
index add4f71..c7becbb 100644
--- a/lisp/game-objects.lisp
+++ b/lisp/game-objects.lisp
@@ -73,6 +73,7 @@
 						   (,command ,game-object)))
 				   (setf (,command ,game-object) NIL)))))
 
+;;; XXX Is this needed? A quick grep doesn't find it anywhere in the code.
 (let ((list-function (make-list-function 'place NIL)))
 	(defun list-place-objects (object-type place)
 		"Get a list of the names of all the place's objects of this type."

diff --git a/lisp/atlantis.lisp b/lisp/atlantis.lisp
index 083b01f..f0d1770 100644
--- a/lisp/atlantis.lisp
+++ b/lisp/atlantis.lisp
@@ -17,8 +17,11 @@
 (load "ui.lisp")
 
 
+(defvar *debugging* NIL)
+
 (defun development ()
 	"A method to easily test whatever feature I am currently developing"
+	(setf *debugging* T)
 	(load-file "../ATL/lisp-test.atl")
 	(let ((player (make-player :name "Bilbo"
 					  :race (get-game-object 'race "Hobbit")
@@ -34,12 +37,13 @@
 
 (defun start-server ()
 	"Start a new game on a server"
+	;; TODO Doesn't actually start a server yet
 	(format t "~&What world file do you want to load?")
 	(input-string world-file) 
 	(format t "~&What port should the game run on?")
 	(while (not (numberp (input port)))
 		(format t "~&Not a number: ~A. Please reenter:" port))
-	(format t "~&Loading file ~S on port ~A" world-file port)
+	(debugging "~&Loading file ~S on port ~A" world-file port)
 	(load-file world-file))
 
 (defun join-game ()
@@ -56,7 +60,7 @@
 	;(setf (cassoc port *server-address*) server-port)
 	(format t "~&What is your player name?")
 	(input-string name)
-	(format t "~&Joining game on ~A:~A as ~A" server-ip server-port name)
+	(debugging "~&Joining game on ~A:~A as ~A" server-ip server-port name)
 	(play-game name))
 
 
@@ -80,7 +84,7 @@
 		(2 (start-menu))))
 
 (defun print-version ()
-	(format t "~&Lisp Atlantis ~A.~A.~A"
+	(format t "~&Atlantis ~A.~A.~A"
 		(first ATLANTIS-VERSION)
 		(second ATLANTIS-VERSION)
 		(third ATLANTIS-VERSION))
@@ -114,32 +118,38 @@
 
 (defun print-help ()
 	(print-version)
-	(format t "~&~%Commandline options:")
-	(let ((tab (string #\Tab)))
-		(format t "~&-v --version~AShow the version number and exit" tab)
-		(format t "~&-h --help~AShow this help text and exit" tab)
-		(format t "~&--license~AShow the license text" tab)
-		(format t "~&--server <port>~AStart a server on <port> (requires --world)" tab)
-		(format t "~&--world <world-file>~AThe ATL file to load (requires --server)" tab)
-		(format t "~&--client <ip>:<port>~AConnect to the game server at <ip>:<port>" tab)))
+	(setf help-text "
+Commandline options:
+-v --version          Show the version number and exit
+-h --help             Show this help text and exit
+--license             Show the license text
+--debugging           Switch on debug mode
+--single-player       Start a single-player game
+--server <port>       Start a server on <port> (requires --world)
+--world <world-file>  The ATL file to load (requires --server)
+--client <ip>:<port>  Connect to the game server at <ip>:<port>")
+	(format t "~A" help-text))
 
 (defun parse-commandline-args ()
 	;; TODO clean this up? (should give error message with unknown params)
-	(when (or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
+	(cond ((or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
 			  (print-version) (quit))
-	(when (or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
-		(print-help) (quit))
-	(when (cmd-parameter "--license" T)
-		(dolist (line (load-text-file "../LICENSE"))
-			(unless (null line) (format t "~%~A" line)))
-		(quit))
+		((or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
+			(print-help) (quit))
+		((cmd-parameter "--license" T)
+			(dolist (line (load-text-file "../LICENSE"))
+				(unless (null line) (format t "~%~A" line)))
+			(quit))
+		((cmd-parameter "--debugging")
+			(setf *debugging* T))
+		((cmd-parameter "--single-player" T)
+			(single-player)))
 	(let ((server (cmd-parameter "--server"))
 			 (world-file (cmd-parameter "--world"))
 			 (client (cmd-parameter "--client")))
 		(unless (or server world-file client)
 			(format t "~&Invalid commandline parameter!") (quit))
-		;; TODO change OR to AND, change function calls
-		(if (or world-file server)
+		(if (and world-file server)
 			(load-file world-file)
 			(join-game))))
 
diff --git a/lisp/game-objects.lisp b/lisp/game-objects.lisp
index add4f71..c7becbb 100644
--- a/lisp/game-objects.lisp
+++ b/lisp/game-objects.lisp
@@ -73,6 +73,7 @@
 						   (,command ,game-object)))
 				   (setf (,command ,game-object) NIL)))))
 
+;;; XXX Is this needed? A quick grep doesn't find it anywhere in the code.
 (let ((list-function (make-list-function 'place NIL)))
 	(defun list-place-objects (object-type place)
 		"Get a list of the names of all the place's objects of this type."
diff --git a/lisp/interpreter.lisp b/lisp/interpreter.lisp
index b0af3c7..211226a 100644
--- a/lisp/interpreter.lisp
+++ b/lisp/interpreter.lisp
@@ -13,7 +13,7 @@
 (defun build-define-command (object-type)
 	"Build a new define command function for the specified object type"
 	#'(lambda (name)
-		  (format t "~&Making ~A ~A"
+		  (debugging "~&Making ~A ~A"
 			  (string-downcase (to-string object-type)) name)
 		  (funcall (build-symbol "make-" object-type) :name name)))
 
@@ -31,7 +31,7 @@
 (defcommand define-weapon weapon)
 
 (defun start-place (place)
-	(format t "~&Starting place is ~A" place)
+	(debugging "~&Starting place is ~A" place)
 	(setf (world-starting-place *world*) place)
 	NIL)
 
@@ -88,6 +88,6 @@
 					(set-object-attribute current-object (read-from-string line)
 						(read-from-string
 							(second (cut-string line (position #\space line))))))
-				(T (format t "~&ERROR: unrecognized syntax on line ~A: '~A'"
+				(T (error "~&ERROR: unrecognized syntax on line ~A: '~A'"
 					   ;; can't happen
 					   (1+ line-nr) line))))))

diff --git a/lisp/atlantis.lisp b/lisp/atlantis.lisp
index 083b01f..f0d1770 100644
--- a/lisp/atlantis.lisp
+++ b/lisp/atlantis.lisp
@@ -17,8 +17,11 @@
 (load "ui.lisp")
 
 
+(defvar *debugging* NIL)
+
 (defun development ()
 	"A method to easily test whatever feature I am currently developing"
+	(setf *debugging* T)
 	(load-file "../ATL/lisp-test.atl")
 	(let ((player (make-player :name "Bilbo"
 					  :race (get-game-object 'race "Hobbit")
@@ -34,12 +37,13 @@
 
 (defun start-server ()
 	"Start a new game on a server"
+	;; TODO Doesn't actually start a server yet
 	(format t "~&What world file do you want to load?")
 	(input-string world-file) 
 	(format t "~&What port should the game run on?")
 	(while (not (numberp (input port)))
 		(format t "~&Not a number: ~A. Please reenter:" port))
-	(format t "~&Loading file ~S on port ~A" world-file port)
+	(debugging "~&Loading file ~S on port ~A" world-file port)
 	(load-file world-file))
 
 (defun join-game ()
@@ -56,7 +60,7 @@
 	;(setf (cassoc port *server-address*) server-port)
 	(format t "~&What is your player name?")
 	(input-string name)
-	(format t "~&Joining game on ~A:~A as ~A" server-ip server-port name)
+	(debugging "~&Joining game on ~A:~A as ~A" server-ip server-port name)
 	(play-game name))
 
 
@@ -80,7 +84,7 @@
 		(2 (start-menu))))
 
 (defun print-version ()
-	(format t "~&Lisp Atlantis ~A.~A.~A"
+	(format t "~&Atlantis ~A.~A.~A"
 		(first ATLANTIS-VERSION)
 		(second ATLANTIS-VERSION)
 		(third ATLANTIS-VERSION))
@@ -114,32 +118,38 @@
 
 (defun print-help ()
 	(print-version)
-	(format t "~&~%Commandline options:")
-	(let ((tab (string #\Tab)))
-		(format t "~&-v --version~AShow the version number and exit" tab)
-		(format t "~&-h --help~AShow this help text and exit" tab)
-		(format t "~&--license~AShow the license text" tab)
-		(format t "~&--server <port>~AStart a server on <port> (requires --world)" tab)
-		(format t "~&--world <world-file>~AThe ATL file to load (requires --server)" tab)
-		(format t "~&--client <ip>:<port>~AConnect to the game server at <ip>:<port>" tab)))
+	(setf help-text "
+Commandline options:
+-v --version          Show the version number and exit
+-h --help             Show this help text and exit
+--license             Show the license text
+--debugging           Switch on debug mode
+--single-player       Start a single-player game
+--server <port>       Start a server on <port> (requires --world)
+--world <world-file>  The ATL file to load (requires --server)
+--client <ip>:<port>  Connect to the game server at <ip>:<port>")
+	(format t "~A" help-text))
 
 (defun parse-commandline-args ()
 	;; TODO clean this up? (should give error message with unknown params)
-	(when (or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
+	(cond ((or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
 			  (print-version) (quit))
-	(when (or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
-		(print-help) (quit))
-	(when (cmd-parameter "--license" T)
-		(dolist (line (load-text-file "../LICENSE"))
-			(unless (null line) (format t "~%~A" line)))
-		(quit))
+		((or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
+			(print-help) (quit))
+		((cmd-parameter "--license" T)
+			(dolist (line (load-text-file "../LICENSE"))
+				(unless (null line) (format t "~%~A" line)))
+			(quit))
+		((cmd-parameter "--debugging")
+			(setf *debugging* T))
+		((cmd-parameter "--single-player" T)
+			(single-player)))
 	(let ((server (cmd-parameter "--server"))
 			 (world-file (cmd-parameter "--world"))
 			 (client (cmd-parameter "--client")))
 		(unless (or server world-file client)
 			(format t "~&Invalid commandline parameter!") (quit))
-		;; TODO change OR to AND, change function calls
-		(if (or world-file server)
+		(if (and world-file server)
 			(load-file world-file)
 			(join-game))))
 
diff --git a/lisp/game-objects.lisp b/lisp/game-objects.lisp
index add4f71..c7becbb 100644
--- a/lisp/game-objects.lisp
+++ b/lisp/game-objects.lisp
@@ -73,6 +73,7 @@
 						   (,command ,game-object)))
 				   (setf (,command ,game-object) NIL)))))
 
+;;; XXX Is this needed? A quick grep doesn't find it anywhere in the code.
 (let ((list-function (make-list-function 'place NIL)))
 	(defun list-place-objects (object-type place)
 		"Get a list of the names of all the place's objects of this type."
diff --git a/lisp/interpreter.lisp b/lisp/interpreter.lisp
index b0af3c7..211226a 100644
--- a/lisp/interpreter.lisp
+++ b/lisp/interpreter.lisp
@@ -13,7 +13,7 @@
 (defun build-define-command (object-type)
 	"Build a new define command function for the specified object type"
 	#'(lambda (name)
-		  (format t "~&Making ~A ~A"
+		  (debugging "~&Making ~A ~A"
 			  (string-downcase (to-string object-type)) name)
 		  (funcall (build-symbol "make-" object-type) :name name)))
 
@@ -31,7 +31,7 @@
 (defcommand define-weapon weapon)
 
 (defun start-place (place)
-	(format t "~&Starting place is ~A" place)
+	(debugging "~&Starting place is ~A" place)
 	(setf (world-starting-place *world*) place)
 	NIL)
 
@@ -88,6 +88,6 @@
 					(set-object-attribute current-object (read-from-string line)
 						(read-from-string
 							(second (cut-string line (position #\space line))))))
-				(T (format t "~&ERROR: unrecognized syntax on line ~A: '~A'"
+				(T (error "~&ERROR: unrecognized syntax on line ~A: '~A'"
 					   ;; can't happen
 					   (1+ line-nr) line))))))
diff --git a/lisp/ui.lisp b/lisp/ui.lisp
index e7eeda8..7ca1edc 100644
--- a/lisp/ui.lisp
+++ b/lisp/ui.lisp
@@ -56,7 +56,8 @@
 		(setf (player-class player)
 			(get-game-object 'character-class character-class))
 		;; Set character attributes
-		(while (< (reduce #'+ character-points) 24) ; Warning: magic number!
+		(while (or (< (reduce #'+ character-points) 24) ; XXX magic number!
+				   (not (set-p character-points)))
 			(set-list (1+ (random 20)) a b c d)
 			(setf character-points (list a b c d)))
 		(setf text "
@@ -74,7 +75,6 @@
 			(while (not (member val character-points))
 				(format t "~&Sorry, invalid number chosen. Please reenter:")
 				(simple-input val (concatenate 'string (symbol-name attr) ":")))
-			;; FIXME Gives problems if two equal numbers are in char-points
 			(let ((player-fn (build-symbol "player-" attr)))
 				;; XXX Kludge ?!
 				(eval `(setf (,player-fn ,player) ,val)))
@@ -157,7 +157,7 @@
 
 (defun goto (player location)
 	"Go to the specified location"
-	(format t "~&~A is going to ~A." (player-name player) location)
+	(debugging "~&~A is going to ~A." (player-name player) location)
 	(when (symbolp location) (setf location (symbol-name location)))
 	(when (not (member location
 				   (place-neighbour (get-game-object 'place

diff --git a/lisp/atlantis.lisp b/lisp/atlantis.lisp
index 083b01f..f0d1770 100644
--- a/lisp/atlantis.lisp
+++ b/lisp/atlantis.lisp
@@ -17,8 +17,11 @@
 (load "ui.lisp")
 
 
+(defvar *debugging* NIL)
+
 (defun development ()
 	"A method to easily test whatever feature I am currently developing"
+	(setf *debugging* T)
 	(load-file "../ATL/lisp-test.atl")
 	(let ((player (make-player :name "Bilbo"
 					  :race (get-game-object 'race "Hobbit")
@@ -34,12 +37,13 @@
 
 (defun start-server ()
 	"Start a new game on a server"
+	;; TODO Doesn't actually start a server yet
 	(format t "~&What world file do you want to load?")
 	(input-string world-file) 
 	(format t "~&What port should the game run on?")
 	(while (not (numberp (input port)))
 		(format t "~&Not a number: ~A. Please reenter:" port))
-	(format t "~&Loading file ~S on port ~A" world-file port)
+	(debugging "~&Loading file ~S on port ~A" world-file port)
 	(load-file world-file))
 
 (defun join-game ()
@@ -56,7 +60,7 @@
 	;(setf (cassoc port *server-address*) server-port)
 	(format t "~&What is your player name?")
 	(input-string name)
-	(format t "~&Joining game on ~A:~A as ~A" server-ip server-port name)
+	(debugging "~&Joining game on ~A:~A as ~A" server-ip server-port name)
 	(play-game name))
 
 
@@ -80,7 +84,7 @@
 		(2 (start-menu))))
 
 (defun print-version ()
-	(format t "~&Lisp Atlantis ~A.~A.~A"
+	(format t "~&Atlantis ~A.~A.~A"
 		(first ATLANTIS-VERSION)
 		(second ATLANTIS-VERSION)
 		(third ATLANTIS-VERSION))
@@ -114,32 +118,38 @@
 
 (defun print-help ()
 	(print-version)
-	(format t "~&~%Commandline options:")
-	(let ((tab (string #\Tab)))
-		(format t "~&-v --version~AShow the version number and exit" tab)
-		(format t "~&-h --help~AShow this help text and exit" tab)
-		(format t "~&--license~AShow the license text" tab)
-		(format t "~&--server <port>~AStart a server on <port> (requires --world)" tab)
-		(format t "~&--world <world-file>~AThe ATL file to load (requires --server)" tab)
-		(format t "~&--client <ip>:<port>~AConnect to the game server at <ip>:<port>" tab)))
+	(setf help-text "
+Commandline options:
+-v --version          Show the version number and exit
+-h --help             Show this help text and exit
+--license             Show the license text
+--debugging           Switch on debug mode
+--single-player       Start a single-player game
+--server <port>       Start a server on <port> (requires --world)
+--world <world-file>  The ATL file to load (requires --server)
+--client <ip>:<port>  Connect to the game server at <ip>:<port>")
+	(format t "~A" help-text))
 
 (defun parse-commandline-args ()
 	;; TODO clean this up? (should give error message with unknown params)
-	(when (or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
+	(cond ((or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
 			  (print-version) (quit))
-	(when (or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
-		(print-help) (quit))
-	(when (cmd-parameter "--license" T)
-		(dolist (line (load-text-file "../LICENSE"))
-			(unless (null line) (format t "~%~A" line)))
-		(quit))
+		((or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
+			(print-help) (quit))
+		((cmd-parameter "--license" T)
+			(dolist (line (load-text-file "../LICENSE"))
+				(unless (null line) (format t "~%~A" line)))
+			(quit))
+		((cmd-parameter "--debugging")
+			(setf *debugging* T))
+		((cmd-parameter "--single-player" T)
+			(single-player)))
 	(let ((server (cmd-parameter "--server"))
 			 (world-file (cmd-parameter "--world"))
 			 (client (cmd-parameter "--client")))
 		(unless (or server world-file client)
 			(format t "~&Invalid commandline parameter!") (quit))
-		;; TODO change OR to AND, change function calls
-		(if (or world-file server)
+		(if (and world-file server)
 			(load-file world-file)
 			(join-game))))
 
diff --git a/lisp/game-objects.lisp b/lisp/game-objects.lisp
index add4f71..c7becbb 100644
--- a/lisp/game-objects.lisp
+++ b/lisp/game-objects.lisp
@@ -73,6 +73,7 @@
 						   (,command ,game-object)))
 				   (setf (,command ,game-object) NIL)))))
 
+;;; XXX Is this needed? A quick grep doesn't find it anywhere in the code.
 (let ((list-function (make-list-function 'place NIL)))
 	(defun list-place-objects (object-type place)
 		"Get a list of the names of all the place's objects of this type."
diff --git a/lisp/interpreter.lisp b/lisp/interpreter.lisp
index b0af3c7..211226a 100644
--- a/lisp/interpreter.lisp
+++ b/lisp/interpreter.lisp
@@ -13,7 +13,7 @@
 (defun build-define-command (object-type)
 	"Build a new define command function for the specified object type"
 	#'(lambda (name)
-		  (format t "~&Making ~A ~A"
+		  (debugging "~&Making ~A ~A"
 			  (string-downcase (to-string object-type)) name)
 		  (funcall (build-symbol "make-" object-type) :name name)))
 
@@ -31,7 +31,7 @@
 (defcommand define-weapon weapon)
 
 (defun start-place (place)
-	(format t "~&Starting place is ~A" place)
+	(debugging "~&Starting place is ~A" place)
 	(setf (world-starting-place *world*) place)
 	NIL)
 
@@ -88,6 +88,6 @@
 					(set-object-attribute current-object (read-from-string line)
 						(read-from-string
 							(second (cut-string line (position #\space line))))))
-				(T (format t "~&ERROR: unrecognized syntax on line ~A: '~A'"
+				(T (error "~&ERROR: unrecognized syntax on line ~A: '~A'"
 					   ;; can't happen
 					   (1+ line-nr) line))))))
diff --git a/lisp/ui.lisp b/lisp/ui.lisp
index e7eeda8..7ca1edc 100644
--- a/lisp/ui.lisp
+++ b/lisp/ui.lisp
@@ -56,7 +56,8 @@
 		(setf (player-class player)
 			(get-game-object 'character-class character-class))
 		;; Set character attributes
-		(while (< (reduce #'+ character-points) 24) ; Warning: magic number!
+		(while (or (< (reduce #'+ character-points) 24) ; XXX magic number!
+				   (not (set-p character-points)))
 			(set-list (1+ (random 20)) a b c d)
 			(setf character-points (list a b c d)))
 		(setf text "
@@ -74,7 +75,6 @@
 			(while (not (member val character-points))
 				(format t "~&Sorry, invalid number chosen. Please reenter:")
 				(simple-input val (concatenate 'string (symbol-name attr) ":")))
-			;; FIXME Gives problems if two equal numbers are in char-points
 			(let ((player-fn (build-symbol "player-" attr)))
 				;; XXX Kludge ?!
 				(eval `(setf (,player-fn ,player) ,val)))
@@ -157,7 +157,7 @@
 
 (defun goto (player location)
 	"Go to the specified location"
-	(format t "~&~A is going to ~A." (player-name player) location)
+	(debugging "~&~A is going to ~A." (player-name player) location)
 	(when (symbolp location) (setf location (symbol-name location)))
 	(when (not (member location
 				   (place-neighbour (get-game-object 'place
diff --git a/lisp/util.lisp b/lisp/util.lisp
index 16b4d49..379ef0d 100644
--- a/lisp/util.lisp
+++ b/lisp/util.lisp
@@ -20,6 +20,10 @@
 			   syms)
 		 ,@body))
 
+(defmacro debugging (str &rest format-args)
+	"If *debugging* is true, print str"
+	`(when *debugging* (format t ,str ,@format-args)))
+
 ;; TODO DEPRECATED - Needs to be replaced in the current code
 (defmacro simple-input (var &optional (prompt ">>>"))
 	"Take input from terminal and store it in var"
@@ -96,7 +100,6 @@
 
 ; Some of these functions are probably quite inefficient (lots of consing)
 
-
 ;; XXX DEPRECATED Not actually needed anywhere
 (defun call-function (function-name &rest args)
 	"Save myself some quoting when calling a function from a generated symbol"
@@ -146,6 +149,12 @@
 			(when (funcall test search-term (elt search-sequence i))
 				(incf count)))))
 
+(defun set-p (lst)
+	"Is lst a set (i.e. no elements occur more than once)?"
+	(cond ((null lst) T)
+		((member (car lst) (cdr lst)) NIL)
+		(T (set-p (cdr lst)))))
+
 (defun to-list (vector &optional (next-elt 0))
 	"Turn the vector into a list"
 	(if (= next-elt (1- (length vector))) NIL

diff --git a/lisp/atlantis.lisp b/lisp/atlantis.lisp
index 083b01f..f0d1770 100644
--- a/lisp/atlantis.lisp
+++ b/lisp/atlantis.lisp
@@ -17,8 +17,11 @@
 (load "ui.lisp")
 
 
+(defvar *debugging* NIL)
+
 (defun development ()
 	"A method to easily test whatever feature I am currently developing"
+	(setf *debugging* T)
 	(load-file "../ATL/lisp-test.atl")
 	(let ((player (make-player :name "Bilbo"
 					  :race (get-game-object 'race "Hobbit")
@@ -34,12 +37,13 @@
 
 (defun start-server ()
 	"Start a new game on a server"
+	;; TODO Doesn't actually start a server yet
 	(format t "~&What world file do you want to load?")
 	(input-string world-file) 
 	(format t "~&What port should the game run on?")
 	(while (not (numberp (input port)))
 		(format t "~&Not a number: ~A. Please reenter:" port))
-	(format t "~&Loading file ~S on port ~A" world-file port)
+	(debugging "~&Loading file ~S on port ~A" world-file port)
 	(load-file world-file))
 
 (defun join-game ()
@@ -56,7 +60,7 @@
 	;(setf (cassoc port *server-address*) server-port)
 	(format t "~&What is your player name?")
 	(input-string name)
-	(format t "~&Joining game on ~A:~A as ~A" server-ip server-port name)
+	(debugging "~&Joining game on ~A:~A as ~A" server-ip server-port name)
 	(play-game name))
 
 
@@ -80,7 +84,7 @@
 		(2 (start-menu))))
 
 (defun print-version ()
-	(format t "~&Lisp Atlantis ~A.~A.~A"
+	(format t "~&Atlantis ~A.~A.~A"
 		(first ATLANTIS-VERSION)
 		(second ATLANTIS-VERSION)
 		(third ATLANTIS-VERSION))
@@ -114,32 +118,38 @@
 
 (defun print-help ()
 	(print-version)
-	(format t "~&~%Commandline options:")
-	(let ((tab (string #\Tab)))
-		(format t "~&-v --version~AShow the version number and exit" tab)
-		(format t "~&-h --help~AShow this help text and exit" tab)
-		(format t "~&--license~AShow the license text" tab)
-		(format t "~&--server <port>~AStart a server on <port> (requires --world)" tab)
-		(format t "~&--world <world-file>~AThe ATL file to load (requires --server)" tab)
-		(format t "~&--client <ip>:<port>~AConnect to the game server at <ip>:<port>" tab)))
+	(setf help-text "
+Commandline options:
+-v --version          Show the version number and exit
+-h --help             Show this help text and exit
+--license             Show the license text
+--debugging           Switch on debug mode
+--single-player       Start a single-player game
+--server <port>       Start a server on <port> (requires --world)
+--world <world-file>  The ATL file to load (requires --server)
+--client <ip>:<port>  Connect to the game server at <ip>:<port>")
+	(format t "~A" help-text))
 
 (defun parse-commandline-args ()
 	;; TODO clean this up? (should give error message with unknown params)
-	(when (or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
+	(cond ((or (cmd-parameter "--version" T) (cmd-parameter "-v" T))
 			  (print-version) (quit))
-	(when (or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
-		(print-help) (quit))
-	(when (cmd-parameter "--license" T)
-		(dolist (line (load-text-file "../LICENSE"))
-			(unless (null line) (format t "~%~A" line)))
-		(quit))
+		((or (cmd-parameter "--help" T) (cmd-parameter "-h" T))
+			(print-help) (quit))
+		((cmd-parameter "--license" T)
+			(dolist (line (load-text-file "../LICENSE"))
+				(unless (null line) (format t "~%~A" line)))
+			(quit))
+		((cmd-parameter "--debugging")
+			(setf *debugging* T))
+		((cmd-parameter "--single-player" T)
+			(single-player)))
 	(let ((server (cmd-parameter "--server"))
 			 (world-file (cmd-parameter "--world"))
 			 (client (cmd-parameter "--client")))
 		(unless (or server world-file client)
 			(format t "~&Invalid commandline parameter!") (quit))
-		;; TODO change OR to AND, change function calls
-		(if (or world-file server)
+		(if (and world-file server)
 			(load-file world-file)
 			(join-game))))
 
diff --git a/lisp/game-objects.lisp b/lisp/game-objects.lisp
index add4f71..c7becbb 100644
--- a/lisp/game-objects.lisp
+++ b/lisp/game-objects.lisp
@@ -73,6 +73,7 @@
 						   (,command ,game-object)))
 				   (setf (,command ,game-object) NIL)))))
 
+;;; XXX Is this needed? A quick grep doesn't find it anywhere in the code.
 (let ((list-function (make-list-function 'place NIL)))
 	(defun list-place-objects (object-type place)
 		"Get a list of the names of all the place's objects of this type."
diff --git a/lisp/interpreter.lisp b/lisp/interpreter.lisp
index b0af3c7..211226a 100644
--- a/lisp/interpreter.lisp
+++ b/lisp/interpreter.lisp
@@ -13,7 +13,7 @@
 (defun build-define-command (object-type)
 	"Build a new define command function for the specified object type"
 	#'(lambda (name)
-		  (format t "~&Making ~A ~A"
+		  (debugging "~&Making ~A ~A"
 			  (string-downcase (to-string object-type)) name)
 		  (funcall (build-symbol "make-" object-type) :name name)))
 
@@ -31,7 +31,7 @@
 (defcommand define-weapon weapon)
 
 (defun start-place (place)
-	(format t "~&Starting place is ~A" place)
+	(debugging "~&Starting place is ~A" place)
 	(setf (world-starting-place *world*) place)
 	NIL)
 
@@ -88,6 +88,6 @@
 					(set-object-attribute current-object (read-from-string line)
 						(read-from-string
 							(second (cut-string line (position #\space line))))))
-				(T (format t "~&ERROR: unrecognized syntax on line ~A: '~A'"
+				(T (error "~&ERROR: unrecognized syntax on line ~A: '~A'"
 					   ;; can't happen
 					   (1+ line-nr) line))))))
diff --git a/lisp/ui.lisp b/lisp/ui.lisp
index e7eeda8..7ca1edc 100644
--- a/lisp/ui.lisp
+++ b/lisp/ui.lisp
@@ -56,7 +56,8 @@
 		(setf (player-class player)
 			(get-game-object 'character-class character-class))
 		;; Set character attributes
-		(while (< (reduce #'+ character-points) 24) ; Warning: magic number!
+		(while (or (< (reduce #'+ character-points) 24) ; XXX magic number!
+				   (not (set-p character-points)))
 			(set-list (1+ (random 20)) a b c d)
 			(setf character-points (list a b c d)))
 		(setf text "
@@ -74,7 +75,6 @@
 			(while (not (member val character-points))
 				(format t "~&Sorry, invalid number chosen. Please reenter:")
 				(simple-input val (concatenate 'string (symbol-name attr) ":")))
-			;; FIXME Gives problems if two equal numbers are in char-points
 			(let ((player-fn (build-symbol "player-" attr)))
 				;; XXX Kludge ?!
 				(eval `(setf (,player-fn ,player) ,val)))
@@ -157,7 +157,7 @@
 
 (defun goto (player location)
 	"Go to the specified location"
-	(format t "~&~A is going to ~A." (player-name player) location)
+	(debugging "~&~A is going to ~A." (player-name player) location)
 	(when (symbolp location) (setf location (symbol-name location)))
 	(when (not (member location
 				   (place-neighbour (get-game-object 'place
diff --git a/lisp/util.lisp b/lisp/util.lisp
index 16b4d49..379ef0d 100644
--- a/lisp/util.lisp
+++ b/lisp/util.lisp
@@ -20,6 +20,10 @@
 			   syms)
 		 ,@body))
 
+(defmacro debugging (str &rest format-args)
+	"If *debugging* is true, print str"
+	`(when *debugging* (format t ,str ,@format-args)))
+
 ;; TODO DEPRECATED - Needs to be replaced in the current code
 (defmacro simple-input (var &optional (prompt ">>>"))
 	"Take input from terminal and store it in var"
@@ -96,7 +100,6 @@
 
 ; Some of these functions are probably quite inefficient (lots of consing)
 
-
 ;; XXX DEPRECATED Not actually needed anywhere
 (defun call-function (function-name &rest args)
 	"Save myself some quoting when calling a function from a generated symbol"
@@ -146,6 +149,12 @@
 			(when (funcall test search-term (elt search-sequence i))
 				(incf count)))))
 
+(defun set-p (lst)
+	"Is lst a set (i.e. no elements occur more than once)?"
+	(cond ((null lst) T)
+		((member (car lst) (cdr lst)) NIL)
+		(T (set-p (cdr lst)))))
+
 (defun to-list (vector &optional (next-elt 0))
 	"Turn the vector into a list"
 	(if (= next-elt (1- (length vector))) NIL
diff --git a/lisp/world.lisp b/lisp/world.lisp
index 4694c78..c6f01fe 100644
--- a/lisp/world.lisp
+++ b/lisp/world.lisp
@@ -53,7 +53,7 @@
 
 (defun name-world (name)
 	"Set the name of the *world*"
-	(format t "~&The name of the world is ~A." name)
+	(debugging "~&The name of the world is ~A." name)
 	(setf (world-name *world*) name)
 	NIL)
 
@@ -62,12 +62,9 @@
 	(with-open-file (g game-file)
 		(let ((version-number (read g))
 				 (loaded-world (read g)))
-			;; XXX This introduces UI in a non-UI module...
 			(when (!= version-number ATLANTIS-VERSION :test equal)
-				(format t "~&WARNING: The loaded world was saved by a different")
-				(format t " version of Atlantis!")
-				(unless (yes-or-no-p "Continue anyway?")
-					(start-menu)))
+				(format t "~&WARNING: The loaded game was saved by a ")
+				(format t "different version of Atlantis!"))
 			(if (world-p loaded-world)
 				(setf *world* loaded-world)
 				(error "World file ~A is corrupted!" game-file)))))