diff --git a/src/mw_engine/core.clj b/src/mw_engine/core.clj
index 2394d8d..fddc229 100644
--- a/src/mw_engine/core.clj
+++ b/src/mw_engine/core.clj
@@ -9,6 +9,10 @@
 ;; fires, it returns a new cell, which should have the same values for :x and
 ;; :y as the old cell. Anything else can be modified.
 ;;
+;; While any function of two arguments can be used as a rule, a special high
+;; level rule language is provided by the `mw-parser` package, which compiles
+;; rules expressed in a subset of English rules into suitable functions.
+;;
 ;; A cell is a map containing at least values for the keys :x, :y, and :state;
 ;; a transformation should not alter the values of :x or :y, and should not
 ;; return a cell without a keyword as the value of :state. Anything else is
@@ -18,7 +22,9 @@
 ;; that every cell's :x and :y properties reflect its place in the matrix.
 ;; See `world.clj`.
 ;;
-;; Rules are applied in turn until one matches.
+;; Each time the world is transformed (see `transform-world`, for each cell, 
+;; rules are applied in turn until one matches. Once one rule has matched no
+;; further rules can be applied.
 
 (defn- transform-cell
   "Derive a cell from this cell of this world by applying these rules."
@@ -60,17 +66,3 @@
   [world init-rules rules generations]
   (let [state {:world (transform-world world init-rules) :rules rules}]
     (take generations (iterate transform-world-state state))))
-
-;; (defn animate-world
-;;   "Run this world with these rules for this number of generations, and return nil
-;;   to avoid cluttering the screen. Principally for debugging.
-
-;;   * `world` a world as discussed above;
-;;   * `init-rules` a sequence of rules as defined above, to be run once to initialise the world;
-;;   * `rules` a sequence of rules as definied above, to be run iteratively for each generation;
-;;   * `generations` an (integer) number of generations."
-;;   [world init-rules rules generations]
-;;   (let [state (list (transform-world world init-rules) rules)]
-;;     (dorun
-;;       (take generations (iterate transform-world-state state)))
-;;     state))
diff --git a/src/mw_engine/heightmap.clj b/src/mw_engine/heightmap.clj
index 447e2f8..fc02d72 100644
--- a/src/mw_engine/heightmap.clj
+++ b/src/mw_engine/heightmap.clj
@@ -17,7 +17,7 @@
   "Surprisingly, Clojure doesn't seem to have an abs function, or else I've 
    missed it. So here's one of my own. Maps natural numbers onto themselves,
    and negative integers onto natural numbers. Also maps negative real numbers
-   onto positive real numbers, but I don't care so much about them.
+   onto positive real numbers.
 
    * `n` a number, on the set of real numbers."
   [n]
@@ -25,8 +25,7 @@
 
 (defn transform-altitude
   "Set the altitude of this cell from the corresponding pixel of this heightmap.
-   If the heightmap you supply is smaller than the world, this will break and 
-   it's ALL YOUR FAULT.
+   If the heightmap you supply is smaller than the world, this will break.
 
    * `cell` a cell, as discussed in world.clj, q.v. Alternatively, a map;
    * `heightmap` an (ideally) greyscale image, whose x and y dimensions should
@@ -45,15 +44,14 @@
 (defn- apply-heightmap-row
   "Set the altitude of each cell in this sequence from the corresponding pixel 
    of this heightmap.
-   If the heightmap you supply is smaller than the world, this will break and 
-   it's ALL YOUR FAULT.
+   If the heightmap you supply is smaller than the world, this will break.
 
    * `row` a row in a world, as discussed in world.clj, q.v. Alternatively, a
      sequence of maps;
    * `heightmap` an (ideally) greyscale image, whose x and y dimensions should
      exceed those of the world of which the `cell` forms part."  
   [row heightmap]
-  (apply vector (map #(transform-altitude %1 heightmap) row)))
+  (apply vector (map #(transform-altitude % heightmap) row)))
 
 (defn apply-heightmap
   "Apply the image file loaded from this path to this world, and return a world whose
@@ -65,4 +63,4 @@
   [world imagepath]
   ;; bizarrely, the collage load-util is working for me, but the imagez version isn't.
   (let [heightmap (filter-image (grayscale)(load-image imagepath))]
-    (apply vector (map #(apply-heightmap-row %1 heightmap) world))))
+    (apply vector (map #(apply-heightmap-row % heightmap) world))))
diff --git a/src/mw_engine/utils.clj b/src/mw_engine/utils.clj
index f69dd78..af78f8e 100644
--- a/src/mw_engine/utils.clj
+++ b/src/mw_engine/utils.clj
@@ -51,7 +51,6 @@
 
 
 (defn get-neighbours
-  ([world x y depth]
     "Get the neighbours to distance depth of the cell at x, y in this world.
 
     * `world` a world, as described in world.clj;
@@ -59,26 +58,27 @@
     * `y` an integer representing an y coordinate in that world;
     * `depth` an integer representing the distance from [x,y] that
       should be searched."
-     (remove nil?
-            (map #(get-cell world (first %) (first (rest %)))
-               (remove #(= % (list x y))
-                 (combo/cartesian-product
-                   (range (- x depth) (+ x depth 1))
-                   (range (- y depth) (+ y depth 1)))))))
-   ([world cell depth] 
-    "Get the neighbours to distance depth of this cell in this world.
+    ([world x y depth]
+      (remove nil?
+              (map #(get-cell world (first %) (first (rest %)))
+                   (remove #(= % (list x y))
+                           (combo/cartesian-product
+                             (range (- x depth) (+ x depth 1))
+                             (range (- y depth) (+ y depth 1)))))))
+    ([world cell depth] 
+      "Get the neighbours to distance depth of this cell in this world.
 
-    * `world` a world, as described in world.clj;
-    * `cell` a cell within that world;
-    * `depth` an integer representing the distance from [x,y] that
-      should be searched."
-    (get-neighbours world (:x cell) (:y cell) depth))
-   ([world cell]
-    "Get the immediate neighbours of this cell in this world
+      * `world` a world, as described in world.clj;
+      * `cell` a cell within that world;
+      * `depth` an integer representing the distance from [x,y] that
+        should be searched."
+      (get-neighbours world (:x cell) (:y cell) depth))
+    ([world cell]
+      "Get the immediate neighbours of this cell in this world
 
-    * `world` a world, as described in world.clj;
-    * `cell` a cell within that world."
-    (get-neighbours world cell 1)))
+      * `world` a world, as described in world.clj;
+      * `cell` a cell within that world."
+      (get-neighbours world cell 1)))
 
 (defn get-neighbours-with-property-value
   "Get the neighbours to distance depth of the cell at x, y in this world which