diff --git a/lisp/2048.el b/lisp/2048.el
index 0fde0e0..35695dd 100644
--- a/lisp/2048.el
+++ b/lisp/2048.el
@@ -35,18 +35,33 @@
 ;;; Code:
 
 (require 'dash)
-(defvar 2048--cell-width 6
-  "Width of number cells for 2048. Should be at least 4 to fit \"2048\".")
-(defvar 2048--board-size 4
-  "Number of tiles on the board for 2048. 4 is the default.")
 
-(defvar 2048--vertical-sep-char ?│
-  "Character to use as a vertical border for 2048 cells.")
-(defvar 2048--horizontal-sep-char ?─
-  "Character to use as a horizontal border for 2048 cells.")
-(defvar 2048--corner-sep-char ?+
-  "Character to use as the intersection between `2048--vertical-sep-char'
-and `2048--horizontal-sep-char'.")
+(defgroup 2048 nil
+  "Play a game of 2048."
+  :prefix "2048--"
+  :group 'games)
+(defvar 2048--cell-width 6
+  "Width of number cells for 2048. Should be at least 4 to fit \"2048\".
+
+Values other than 6 are not currently supported.")
+(defcustom 2048--board-size 4
+  "Number of tiles on the board for 2048. 4 is the default.  Can be any number."
+  :type 'integer
+  :group '2048)
+
+(defcustom 2048--vertical-sep-char ?│ ; 9478
+  "Character to use as a vertical border for 2048 cells."
+  :type 'character
+  :group '2048)
+(defcustom 2048--horizontal-sep-char ?─ ; 9472
+  "Character to use as a horizontal border for 2048 cells."
+  :type 'character
+  :group '2048)
+(defcustom 2048--corner-sep-char ?+
+  ;; ?╬ ; needlessly fancy version
+  "Intersection of `2048--vertical-sep-char'and `2048--horizontal-sep-char'."
+  :type 'character
+  :group '2048)
 
 (defun 2048--make-sep-times (delimiter filler cells cellwidth)
   "Return a string of CELLS number of cells, each with width CELLWIDTH.
@@ -58,11 +73,10 @@ The cells consist of FILLER and are separated by DELIMITER."
     (concat (flatten-tree (list delimiter almost-done-list)))))
 ;; (2048--make-sep-times ?> ?- 5 2)
 
-(setq 2048-plus-sep (2048--make-sep-times
+(defvar 2048-plus-sep (2048--make-sep-times
 		     2048--corner-sep-char 2048--horizontal-sep-char
-		     ;; ?╬ ?─ ; needlessly fancy version
 		     2048--board-size 2048--cell-width))
-(setq 2048-space-sep (2048--make-sep-times
+(defvar 2048-space-sep (2048--make-sep-times
 		      2048--vertical-sep-char (string-to-char " ")
 		      2048--board-size 2048--cell-width))
 (defun 2048--pad (number)