diff --git a/Detrospector/Main.hs b/Detrospector/Main.hs
--- a/Detrospector/Main.hs
+++ b/Detrospector/Main.hs
@@ -16,6 +16,7 @@
       += Arg.program "detrospector"
       += Arg.summary "detrospector: Markov chain text generator"
       += Arg.help    "Build and run Markov chains for text generation"
+      += Arg.helpArg [Arg.name "h"]
   where
 
   train = Arg.record Train{}
diff --git a/Detrospector/Modes/Neolog.hs b/Detrospector/Modes/Neolog.hs
--- a/Detrospector/Modes/Neolog.hs
+++ b/Detrospector/Modes/Neolog.hs
@@ -22,7 +22,7 @@
 
   loop !wd = do
     xs  <- fmap toLower <$> make emptyQ emptyQ
-    wdd <- if (qLength xs >= minLen) && HS.notMember xs wd
+    wdd <- if (qLength xs >= minLen) && not (HS.member xs wd)
       then putStrLn (queueToList xs) >> return (HS.insert xs wd)
       else return wd
     loop wdd
diff --git a/Detrospector/Modes/Run.hs b/Detrospector/Modes/Run.hs
--- a/Detrospector/Modes/Run.hs
+++ b/Detrospector/Modes/Run.hs
@@ -7,10 +7,10 @@
 
 go :: Chain -> RNG -> IO ()
 go c@(Chain n _) g = loop emptyQ where
-    loop s = do
-      (x,_) <- pick c s g
-      putChar x
-      loop $! shift n x s
+  loop s = do
+    (x,_) <- pick c s g
+    putChar x
+    loop $! shift n x s
 
 run :: ModeFun
 run Run{chain} = withChain chain go
diff --git a/Detrospector/Modes/Train.hs b/Detrospector/Modes/Train.hs
--- a/Detrospector/Modes/Train.hs
+++ b/Detrospector/Modes/Train.hs
@@ -7,13 +7,13 @@
 import Detrospector.Modes
 
 import System.IO
-import qualified Data.Text         as TS
-import qualified Data.Text.Lazy    as TL
-import qualified Data.Text.Lazy.IO as TL
-import qualified Data.HashMap      as H
-import qualified Data.IntMap       as IM
-import qualified Data.Sequence     as S
-import qualified Data.Foldable     as F
+import qualified Data.Text           as TS
+import qualified Data.Text.Lazy      as TL
+import qualified Data.Text.Lazy.IO   as TL
+import qualified Data.HashMap.Strict as H
+import qualified Data.IntMap         as IM
+import qualified Data.Sequence       as S
+import qualified Data.Foldable       as F
 
 -- foldl' with progress dots
 progFold :: (a -> b -> a) -> a -> [b] -> IO a
@@ -21,6 +21,9 @@
   go !v []     = return v
   go !v (x:xs) = putChar '.' >> go (f v x) xs
 
+-- The guts of a Chain, before we apply 'cumulate'.
+type FreqChain = H.HashMap (S.Seq Char) FreqTable
+
 -- Build a Markov chain with n-Char history from some input text.
 train :: ModeFun
 train Train{num,out} = do
@@ -31,16 +34,23 @@
   putStrLn "done."
   writeChain out . Chain num $ H.map cumulate h where
 
-  roll (!s,!h) x
-    = (shift num x s, F.foldr (H.alter $ ins x) h $ S.tails s)
+  -- Process another character, updating a fold state of the Markov chain
+  -- history and the accumulated FreqChain.
+  roll :: (S.Seq Char, FreqChain) -> Char -> (S.Seq Char, FreqChain)
+  roll (!s, !fci) x = (shift num x s, F.foldr occur fci $ S.tails s) where
 
-  ins x Nothing  = Just $! sing x
-  ins x (Just v) = Just $! incr x v
+    -- Increment the occurrence count for 'x' following history 'hist'.
+    occur :: S.Seq Char -> FreqChain -> FreqChain
+    occur hist fc = H.insert hist (bump $ H.lookup hist fc) fc
 
-  sing x = IM.singleton (fromEnum x) 1
+    -- Given a FreqTable (or Nothing), return a FreqTable with one more
+    -- count for 'x'.
+    bump :: Maybe FreqTable -> FreqTable
+    bump Nothing  = IM.singleton (fromEnum x) 1
+    bump (Just v) = IM.alter incMaybe (fromEnum x) v
 
-  incr x = IM.alter f $ fromEnum x where
-    f Nothing  = Just 1
-    f (Just v) = Just $! (v+1)
+    incMaybe :: Maybe Int -> Maybe Int
+    incMaybe Nothing  = Just 1
+    incMaybe (Just n) = Just $! (n+1)
 
 train _ = error "impossible: wrong mode passed to train"
diff --git a/Detrospector/Types.hs b/Detrospector/Types.hs
--- a/Detrospector/Types.hs
+++ b/Detrospector/Types.hs
@@ -16,7 +16,7 @@
 import Data.Maybe
 import Data.List
 import Control.Applicative
-import qualified Data.HashMap           as H
+import qualified Data.HashMap.Strict    as H
 import qualified Data.Hashable          as H
 import qualified Data.IntMap            as IM
 import qualified System.Random.MWC      as RNG
@@ -106,7 +106,7 @@
 -- orphan instance: Binary serialization of HashMap
 instance (Bin.Binary k, Bin.Binary v, H.Hashable k, Ord k)
        => Bin.Binary (H.HashMap k v) where
-  put = Bin.put . H.assocs
+  put = Bin.put . H.toList
   get = H.fromList <$> Bin.get
   
 instance Bin.Binary PickTable where
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) Keegan McAllister 2010
+Copyright (c) Keegan McAllister 2010 - 2012
 
 All rights reserved.
 
diff --git a/README b/README
new file mode 100644
--- /dev/null
+++ b/README
@@ -0,0 +1,6 @@
+detrospector is a Markov chain text generator.
+
+See detrospector.cabal for more information, as well as
+
+  http://hackage.haskell.org/package/detrospector
+  http://mainisusuallyafunction.blogspot.com/2010/10/tour-of-real-toy-haskell-program-part-1.html
diff --git a/detrospector.cabal b/detrospector.cabal
--- a/detrospector.cabal
+++ b/detrospector.cabal
@@ -1,5 +1,5 @@
 name:                detrospector
-version:             0.1
+version:             0.2
 license:             BSD3
 license-file:        LICENSE
 synopsis:            Markov chain text generator
@@ -7,7 +7,7 @@
 author:              Keegan McAllister <mcallister.keegan@gmail.com>
 maintainer:          Keegan McAllister <mcallister.keegan@gmail.com>
 build-type:          Simple
-cabal-version:       >=1.2
+cabal-version:       >=1.6
 description:
   The `detrospector' program generates random text conforming to the general
   style and diction of a given source document.  It associates each
@@ -23,7 +23,19 @@
   .
   Design goals include speed and full Unicode support.  I welcome suggestions
   and patches regarding any aspect of this program.
+  .
+  New in version 0.2:
+  .
+    * Use the @unordered-containers@ library instead of @hashmap@.  Also fixes
+      a build failure.
+  .
+    * Accept @-h@ for help, in addition to @-?@.
+  .
+    * Added public GitHub repository.
 
+extra-source-files:
+    README
+
 executable detrospector
   main-is:       detrospector.hs
   other-modules:
@@ -43,5 +55,9 @@
     cmdargs    >= 0.6,
     mwc-random >= 0.8,
     hashable   >= 1.0,
-    hashmap    >= 1.1
+    unordered-containers >= 0.1
   ghc-options: -Wall
+
+source-repository head
+  type:     git
+  location: git://github.com/kmcallister/detrospector.git