diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,22 @@
+# Changelog
+
+## 0.3.2.1
+* Relaxed optparse-applicative upper bound.
+
+## 0.3.2
+* Fixed some dimensions minifying incorrectly.
+* Fixed some Eq instances.
+* <An+B> values data type modified to disallow invalid values. This makes the
+  data type safer, also simplifying the Quickcheck Arbitrary instance.
+* Improved test coverage.
+
+## 0.3.1.3
+* Added support for `@supports` rules, and a slight minification for them: it
+  removes adjacent negations, i.e.: @supports not (not ...) gets turn into
+  @supports ....
+* Fixed a small bug with `:lang()` where spaces before the right parenthesis
+  weren't being removed.
+* Improved test coverage.
+
+## 0.3.0.1
+Initial release
diff --git a/benchmarks/Benchmarks.hs b/benchmarks/Benchmarks.hs
new file mode 100644
--- /dev/null
+++ b/benchmarks/Benchmarks.hs
@@ -0,0 +1,11 @@
+import System.Directory (getDirectoryContents, setCurrentDirectory)
+import Criterion.Main
+import qualified Data.Text.IO as TIO
+import Hasmin
+
+main :: IO ()
+main = do
+    setCurrentDirectory "../hasmin-benchmarks/bnch"
+    xs <- getDirectoryContents "."
+    ys <- traverse TIO.readFile (filter (flip notElem [".", ".."]) xs)
+    defaultMain [bgroup "minification" [bench "a" $ nf (map minifyCSS) ys]]
diff --git a/hasmin.cabal b/hasmin.cabal
--- a/hasmin.cabal
+++ b/hasmin.cabal
@@ -1,5 +1,5 @@
 name:                hasmin
-version:             0.3.2
+version:             0.3.2.1
 license:             BSD3
 license-file:        LICENSE
 author:              (c) 2017 Cristian Adrián Ontivero <cristianontivero@gmail.com>
@@ -10,6 +10,7 @@
 category:            Text
 build-type:          Simple
 extra-source-files:  README.md
+                     CHANGELOG.md
 cabal-version:       >=1.10
 description:
     A CSS minifier which not only aims at reducing the amount of bytes of the
@@ -35,7 +36,7 @@
   build-depends:       base                 >=4.9        && <5.1
                      , attoparsec           >=0.12       && <0.14
                      , containers           >=0.5        && <0.6
-                     , optparse-applicative >=0.11       && <0.14
+                     , optparse-applicative >=0.11       && <0.15
                      , parsers              >=0.12.3     && <0.13
                      , text                 >=1.2        && <1.3
                      , hopfli               >=0.2        && <0.4
@@ -130,4 +131,16 @@
                      , doctest          >=0.11    && <0.12
                      , doctest-discover >=0.1.0.0 && <0.2
                      , doctest          >=0.10
+                     , hasmin
+
+benchmark bench
+  default-language:    Haskell2010
+  type:                exitcode-stdio-1.0
+  hs-source-dirs:      benchmarks
+  main-is:             Benchmarks.hs
+  ghc-options:         -threaded -Wall -fno-warn-orphans
+  build-depends:       base             >=4.9  && <5.1
+                     , criterion        >=0.11 && <1.2
+                     , directory
+                     , text             >=1.2  && <1.3
                      , hasmin
diff --git a/src/Hasmin/Parser/Internal.hs b/src/Hasmin/Parser/Internal.hs
--- a/src/Hasmin/Parser/Internal.hs
+++ b/src/Hasmin/Parser/Internal.hs
@@ -18,8 +18,7 @@
     ) where
 
 import Control.Arrow (first)
-import Control.Applicative ((<|>), many, some)
-import Control.Monad (mzero)
+import Control.Applicative ((<|>), many, some, empty)
 import qualified Data.List.NonEmpty as NE
 import Data.Functor (($>))
 import Data.Attoparsec.Combinator (lookAhead, sepBy, endOfInput)
@@ -161,7 +160,7 @@
           where handleSpecialCase :: Text -> Parser SimpleSelector
                 handleSpecialCase t = if T.toCaseFold t `elem` specialPseudoElements
                                          then pure $ PseudoElem t
-                                         else mzero
+                                         else empty
 
 -- \<An+B> microsyntax parser.
 anplusb :: Parser AnPlusB
diff --git a/src/Hasmin/Properties.hs b/src/Hasmin/Properties.hs
--- a/src/Hasmin/Properties.hs
+++ b/src/Hasmin/Properties.hs
@@ -32,6 +32,8 @@
 shorthandAndLonghandsMap :: Map Text PropertyInfo
 shorthandAndLonghandsMap = Map.fromList properties
 
+-- This holds the information of which shorthand overwrites which longhand, and
+-- vice versa (which longhand is overwritten by which shorthand).
 properties :: [(Text,PropertyInfo)]
 properties =
   [("animation", PropertyInfo mempty ["animation-name","animation-duration","animation-timing-function","animation-delay","animation-iteration-count","animation-direction","animation-fill-mode","animation-play-state"])