diff --git a/GOL/Engine.hs b/GOL/Engine.hs
index 77cabaa..9e97178 100644
--- a/GOL/Engine.hs
+++ b/GOL/Engine.hs
@@ -9,6 +9,9 @@ import Data.Bool (bool)
 import GOL.Rule
 import GOL.Space
 
+-- | The comonad stack used in the Game of Life engine.
+-- It consists of a store comonad over the space @f@,
+-- with an environment containing a rule.
 type GOL f = EnvT Rule (Store f)
 
 getNeighbors :: forall f a. Space f => GOL f a -> [a]
@@ -16,15 +19,15 @@ getNeighbors = experiment $ neighbors @f
 
 nextState :: Space f => GOL f Bool -> Bool
 nextState = do
-  selfState <- extract
   neighborStates <- getNeighbors
   let count = sum . fmap (bool 0 1) $ neighborStates
-  
-  Rule survive birth <- ask
-  return $ if selfState
-            then survive count
-            else birth count
 
+  selfState <- extract
+  Rule survive birth <- ask
+  return $
+    if selfState
+      then survive count
+      else birth count
 
 tick :: Space f => GOL f Bool -> GOL f Bool
 tick = extend nextState
\ No newline at end of file
diff --git a/GOL/Space.hs b/GOL/Space.hs
index 6bc231d..890e9b3 100644
--- a/GOL/Space.hs
+++ b/GOL/Space.hs
@@ -6,8 +6,23 @@ module GOL.Space where
 
 import Data.Functor.Rep
 
+-- | A space in which a Conway's Game of Life simulation
+-- takes place, with a notion of "neighbors to a cell" defined.
+--
+-- More specifically, a space is a representable functor @f@ such
+-- that @'Rep' f@ is a graph. 'neighbors' then takes a node of
+-- that graph and returns all nodes that are adjacent.
+--
+-- Instances should satisfy:
+--
+-- * Symmetry: if @x '`elem`' 'neighbors' y@, then @y '`elem`' 'neighbors' x@.
+--
+-- * Irreflexivity: @x '`elem`' 'neighbors' x@ is always false.
 class Representable f => Space f where
   neighbors :: Rep f -> [Rep f]
 
+-- | A space is _displayable_ if it is representable over a 2D
+-- grid. The graphical system requires a displayable space.
 class (Space f, Rep f ~ (Int, Int)) => DisplayableSpace f where
-  size :: (Int, Int)
\ No newline at end of file
+  sizex :: Int
+  sizey :: Int
\ No newline at end of file