diff --git a/mealy.cabal b/mealy.cabal
--- a/mealy.cabal
+++ b/mealy.cabal
@@ -1,26 +1,27 @@
 cabal-version: 2.4
 name:          mealy
-version:       0.1.0
+version:       0.2.0
 license:       BSD-3-Clause
-copyright:     Tony Day (c) AfterTimes
+copyright:     Tony Day (c) 2013 - 2022
 maintainer:    tonyday567@gmail.com
 author:        Tony Day
 homepage:      https://github.com/tonyday567/mealy#readme
 bug-reports:   https://github.com/tonyday567/mealy/issues
 synopsis:      Mealy machines for processing time-series and ordered data.
-description:   @mealy@ provides support for computing statistics (such as an average or a standard deviation)
-     as current state. Usage is to supply a decay function representing the relative weights of recent values versus older ones, in the manner of exponentially-weighted averages. The library attempts to be polymorphic in the statistic which can be combined in applicative style.
-    .
-    == Usage
-    .
-    >>> import Mealy
-    .
-    >>> fold ((,) <$> ma 0.9 <*> std 0.9) [1..100]
-    (91.00265621044142,9.472822805289121)
+description:
+  @mealy@ provides support for computing statistics (such as an average or a standard deviation)
+  as current state. Usage is to supply a decay function representing the relative weights of recent values versus older ones, in the manner of exponentially-weighted averages. The library attempts to be polymorphic in the statistic which can be combined in applicative style.
+  .
+  == Usage
+  .
+  >>> import Mealy
+  .
+  >>> fold ((,) <$> ma 0.9 <*> std 0.9) [1..100]
+  (91.00265621044142,9.472822805289121)
 
 category:      folding
 build-type:    Simple
-tested-with:   GHC ==8.8.4 || ==8.10.4 || ==9.0.1 || ==9.2.0.20210821
+tested-with:   GHC ==8.8.4 || ==8.10.7 || ==9.2.1
 
 source-repository head
   type:     git
@@ -37,19 +38,18 @@
   ghc-options:
     -Wall -Wcompat -Wincomplete-record-updates
     -Wincomplete-uni-patterns -Wredundant-constraints -fwrite-ide-info
-    -hiedir=.hie -Wunused-packages
+    -hiedir=.hie
 
   build-depends:
     , adjunctions        ^>=4.4
-    , base               >=4.13 && <5
+    , base               >=4.13   && <5
     , containers         ^>=0.6.2
     , folds              ^>=0.7.6
-    , generic-lens       ^>=2.2.0
-    , lens               ^>=5.0.1
     , matrix             ^>=0.3.6
     , mwc-probability    ^>=2.3.1
-    , numhask            ^>=0.8.1
-    , numhask-array      ^>=0.9.1
+    , numhask            ^>=0.10
+    , numhask-array      ^>=0.10
+    , optics-core        ^>=0.4
     , primitive          ^>=0.7.2
     , profunctors        ^>=5.6.2
     , tdigest            ^>=0.2.1
diff --git a/src/Data/Mealy.hs b/src/Data/Mealy.hs
--- a/src/Data/Mealy.hs
+++ b/src/Data/Mealy.hs
@@ -71,12 +71,11 @@
 
 import Control.Category
 import Control.Exception
-import Control.Lens hiding (Empty, Unwrapped, Wrapped, index, (:>), (|>))
 import Data.Fold hiding (M)
 import Data.Functor.Rep
-import Data.Generics.Labels ()
 import Data.List (scanl')
 import qualified Data.Matrix as M
+import Data.Profunctor
 import Data.Sequence (Seq)
 import qualified Data.Sequence as Seq
 import Data.Text (Text)
@@ -85,6 +84,7 @@
 import qualified NumHask.Array.Fixed as F
 import NumHask.Array.Shape (HasShape)
 import NumHask.Prelude hiding (L1, asum, fold, id, (.))
+import Optics.Core
 
 -- $setup
 --
@@ -213,7 +213,6 @@
 -- Applicative-style exponentially-weighted standard deviation computation:
 --
 -- > std r = (\s ss -> sqrt (ss - s ** 2)) <$> ma r <*> sqma r
---
 online :: (Divisive b, Additive b) => (a -> b) -> (b -> b) -> Mealy a b
 online f g = M intract step av
   where
@@ -232,7 +231,6 @@
 --
 -- >>> fold (ma 0.99) xs0
 -- 9.713356299018187e-2
---
 ma :: (Divisive a, Additive a) => a -> Mealy a a
 ma r = online id (* r)
 {-# INLINEABLE ma #-}
@@ -271,7 +269,6 @@
 --
 -- >>> fold (std 1) xs0
 -- 1.0126438036262801
---
 std :: (Divisive a, ExpField a) => a -> Mealy a a
 std r = (\s ss -> sqrt (ss - s ** (one + one))) <$> ma r <*> sqma r
 {-# INLINEABLE std #-}
@@ -510,7 +507,6 @@
 -- >>> let xsb0 = fold (beta1 (ma (1 - 0.001))) $ drop 1 $ zip ma' xs0
 -- >>> xsb - xsb0
 -- 0.10000000000000009
---
 depState :: (a -> b -> a) -> Mealy a b -> Mealy a a
 depState f (M sInject sStep sExtract) = M inject step extract
   where
@@ -543,7 +539,7 @@
 -- | Apply a model1 relationship using a single decay factor.
 --
 -- >>> :set -XOverloadedLabels
--- >>> import Control.Lens
+-- >>> import Optics.Core
 -- >>> fold (depModel1 0.01 (zeroModel1 & #betaMa2X .~ 0.1)) xs0
 -- -0.4591515493154126
 depModel1 :: Double -> Model1 -> Mealy Double Double