diff --git a/.github/workflows/build-ci.yml b/.github/workflows/build-ci.yml
index 5e9964c..8779772 100644
--- a/.github/workflows/build-ci.yml
+++ b/.github/workflows/build-ci.yml
@@ -60,7 +60,7 @@ jobs:
   linux5:
     strategy:
       matrix: 
-        resolver: [lts-10, lts-11, lts-12, lts-13, lts-14, lts-15, lts-16, lts-17, lts-18, lts-19, lts-20, lts-21]
+        resolver: [lts-10, lts-11, lts-12, lts-13, lts-14, lts-15, lts-16, lts-18, lts-19, lts-20, lts-21]
 
     name: Run the tests
     runs-on: ubuntu-latest
diff --git a/css-selectors.cabal b/css-selectors.cabal
index 84010f2..ae94476 100644
--- a/css-selectors.cabal
+++ b/css-selectors.cabal
@@ -66,7 +66,7 @@ test-suite css-selectors-test
   main-is:             Spec.hs
   build-depends:
       base
-    , binary >=0.2 && <0.8.8.0
+    , binary >=0.2
     , css-selectors
     , hashable >=1.2.7.0
     , text
diff --git a/src/Css/Selector.hs b/src/Css/Selector.hs
index 483822f..b7bf142 100644
--- a/src/Css/Selector.hs
+++ b/src/Css/Selector.hs
@@ -1,14 +1,15 @@
-{-|
-Module      : Css.Selector
-Description : Css 3 selectors in Haskell.
-Maintainer  : hapytexeu+gh@gmail.com
-Stability   : experimental
-Portability : POSIX
-
-A module for backwards compatibility that re-exports 'Css3.Selector'. This module is deprecated and eventually will be removed.
--}
-module Css.Selector {-# DEPRECATED "Use Css3.Selector instead" #-} (
-    module Css3.Selector,
-  ) where
+-- |
+-- Module      : Css.Selector
+-- Description : Css 3 selectors in Haskell.
+-- Maintainer  : hapytexeu+gh@gmail.com
+-- Stability   : experimental
+-- Portability : POSIX
+--
+-- A module for backwards compatibility that re-exports 'Css3.Selector'. This module is deprecated and eventually will be removed.
+module Css.Selector
+  {-# DEPRECATED "Use Css3.Selector instead" #-}
+  ( module Css3.Selector,
+  )
+where
 
 import Css3.Selector
diff --git a/src/Css/Selector/Core.hs b/src/Css/Selector/Core.hs
index d09b9ee..37b18de 100644
--- a/src/Css/Selector/Core.hs
+++ b/src/Css/Selector/Core.hs
@@ -1,14 +1,15 @@
-{-|
-Module      : Css.Selector.Core
-Description : A module where we define the tree of types to represent and maniplate a css selector.
-Maintainer  : hapytexeu+gh@gmail.com
-Stability   : experimental
-Portability : POSIX
-
-A module for backwards compatibility that re-exports 'Css3.Selector.Core'. This module is deprecated and eventually will be removed.
--}
-module Css.Selector.Core {-# DEPRECATED "Use Css3.Selector.Core instead" #-} (
-    module Css3.Selector.Core
-  ) where
+-- |
+-- Module      : Css.Selector.Core
+-- Description : A module where we define the tree of types to represent and maniplate a css selector.
+-- Maintainer  : hapytexeu+gh@gmail.com
+-- Stability   : experimental
+-- Portability : POSIX
+--
+-- A module for backwards compatibility that re-exports 'Css3.Selector.Core'. This module is deprecated and eventually will be removed.
+module Css.Selector.Core
+  {-# DEPRECATED "Use Css3.Selector.Core instead" #-}
+  ( module Css3.Selector.Core,
+  )
+where
 
 import Css3.Selector.Core
diff --git a/src/Css/Selector/QuasiQuoters.hs b/src/Css/Selector/QuasiQuoters.hs
index 4f00b57..3f9fae5 100644
--- a/src/Css/Selector/QuasiQuoters.hs
+++ b/src/Css/Selector/QuasiQuoters.hs
@@ -1,14 +1,15 @@
-{-|
-Module      : Css.Selector.QuasiQuoters
-Description : A module that defines a quasiquoter to parse a string to a css selector.
-Maintainer  : hapytexeu+gh@gmail.com
-Stability   : experimental
-Portability : POSIX
-
-A module for backwards compatibility that re-exports 'Css3.Selector.QuasiQuoters'. This module is deprecated and eventually will be removed.
--}
-module Css.Selector.QuasiQuoters {-# DEPRECATED "Use Css3.Selector.QuasiQuoters instead" #-} (
-    module Css3.Selector.QuasiQuoters
-  ) where
+-- |
+-- Module      : Css.Selector.QuasiQuoters
+-- Description : A module that defines a quasiquoter to parse a string to a css selector.
+-- Maintainer  : hapytexeu+gh@gmail.com
+-- Stability   : experimental
+-- Portability : POSIX
+--
+-- A module for backwards compatibility that re-exports 'Css3.Selector.QuasiQuoters'. This module is deprecated and eventually will be removed.
+module Css.Selector.QuasiQuoters
+  {-# DEPRECATED "Use Css3.Selector.QuasiQuoters instead" #-}
+  ( module Css3.Selector.QuasiQuoters,
+  )
+where
 
 import Css3.Selector.QuasiQuoters
diff --git a/src/Css/Selector/Utils.hs b/src/Css/Selector/Utils.hs
index be386b0..a99e6b0 100644
--- a/src/Css/Selector/Utils.hs
+++ b/src/Css/Selector/Utils.hs
@@ -1,14 +1,15 @@
-{-|
-Module      : Css.Selector.Utils
-Description : A set of utility methods to encode and decode strings.
-Maintainer  : hapytexeu+gh@gmail.com
-Stability   : experimental
-Portability : POSIX
-
-A module for backwards compatibility that re-exports 'Css3.Selector.Utils'. This module is deprecated and eventually will be removed.
--}
-module Css.Selector.Utils {-# DEPRECATED "Use Css3.Selector.Utils instead" #-} (
-  module Css3.Selector.Utils
-  ) where
+-- |
+-- Module      : Css.Selector.Utils
+-- Description : A set of utility methods to encode and decode strings.
+-- Maintainer  : hapytexeu+gh@gmail.com
+-- Stability   : experimental
+-- Portability : POSIX
+--
+-- A module for backwards compatibility that re-exports 'Css3.Selector.Utils'. This module is deprecated and eventually will be removed.
+module Css.Selector.Utils
+  {-# DEPRECATED "Use Css3.Selector.Utils instead" #-}
+  ( module Css3.Selector.Utils,
+  )
+where
 
 import Css3.Selector.Utils
diff --git a/src/Css3/Selector.hs b/src/Css3/Selector.hs
index 19f7724..d86f7ad 100644
--- a/src/Css3/Selector.hs
+++ b/src/Css3/Selector.hs
@@ -1,17 +1,17 @@
-{-|
-Module      : Css3.Selector
-Description : Css 3 selectors in Haskell.
-Maintainer  : hapytexeu+gh@gmail.com
-Stability   : experimental
-Portability : POSIX
-
-A module to define css selectors by making use of a quasiquoter, and manipulating these css selectors.
--}
-module Css3.Selector (
-    module Css3.Selector.Core,
+-- |
+-- Module      : Css3.Selector
+-- Description : Css 3 selectors in Haskell.
+-- Maintainer  : hapytexeu+gh@gmail.com
+-- Stability   : experimental
+-- Portability : POSIX
+--
+-- A module to define css selectors by making use of a quasiquoter, and manipulating these css selectors.
+module Css3.Selector
+  ( module Css3.Selector.Core,
     module Css3.Selector.QuasiQuoters,
-    module Css3.Selector.Utils
-  ) where
+    module Css3.Selector.Utils,
+  )
+where
 
 import Css3.Selector.Core
 import Css3.Selector.QuasiQuoters
diff --git a/src/Css3/Selector/Core.hs b/src/Css3/Selector/Core.hs
index 5dad421..703591f 100644
--- a/src/Css3/Selector/Core.hs
+++ b/src/Css3/Selector/Core.hs
@@ -813,17 +813,19 @@ instance IsList SelectorGroup where
 _textToPattern :: Text -> Pat
 _textToPattern t = ViewP (AppE (ConE '(==)) (AppE (ConE 'pack) (LitE (StringL (unpack t))))) (_constantP 'True)
 
-_constantP :: Name -> Pat
 #if MIN_VERSION_template_haskell(2,18,0)
+_constantP :: Name -> Pat
 _constantP = flip (`ConP` []) []
 #else
+_constantP :: Name -> Pat
 _constantP = (`ConP` [])
 #endif
 
-_conP :: Name -> [Pat] -> Pat
 #if MIN_VERSION_template_haskell(2,18,0)
+_conP :: Name -> [Pat] -> Pat
 _conP = (`ConP` [])
 #else
+_conP :: Name -> [Pat] -> Pat
 _conP = ConP
 #endif
 
@@ -1327,10 +1329,11 @@ instance Binary SelectorGroup where
 -- Lift instances
 #if MIN_VERSION_template_haskell(2,17,0)
 _apply :: Quote m => Name -> [m Exp] -> m Exp
+_apply = foldl appE . conE
 #else
 _apply :: Name -> [Q Exp] -> Q Exp
-#endif
 _apply = foldl appE . conE
+#endif
 
 instance Lift SelectorGroup where
     lift (SelectorGroup sg) = _apply 'SelectorGroup [liftNe sg]
@@ -1532,7 +1535,7 @@ instance Arbitrary Class where
     shrink (Class a) = Class <$> _shrinkIdent a
 
 instance Arbitrary Nth where
-    arbitrary = Nth <$> ((1+) . abs <$> arbitrary) <*> arbitrary
+    arbitrary = Nth . (1+) . abs <$> arbitrary <*> arbitrary
     shrink nth
       | nth == nnth = []
       | otherwise = [nnth]
diff --git a/src/Css3/Selector/QuasiQuoters.hs b/src/Css3/Selector/QuasiQuoters.hs
index e5e9178..065fa76 100644
--- a/src/Css3/Selector/QuasiQuoters.hs
+++ b/src/Css3/Selector/QuasiQuoters.hs
@@ -1,35 +1,39 @@
 {-# LANGUAGE TemplateHaskellQuotes #-}
 
-{-|
-Module      : Css3.Selector.QuasiQuoters
-Description : A module that defines a quasiquoter to parse a string to a css selector.
-Maintainer  : hapytexeu+gh@gmail.com
-Stability   : experimental
-Portability : POSIX
-
-A module that defines a quasiquoter to parse a string to a css selector.
--}
-module Css3.Selector.QuasiQuoters (
-    csssel, cssselFile, parseCss
-  ) where
-
-import Css3.Selector.Core(SelectorGroup, toPattern)
-import Css3.Selector.Lexer(alexScanTokens)
-import Css3.Selector.Parser(cssselector)
-
-import Data.Data(Data, cast)
-import Data.Text(pack, unpack)
-
-import Language.Haskell.TH.Quote(QuasiQuoter(QuasiQuoter, quoteExp, quotePat, quoteType, quoteDec), quoteFile)
-import Language.Haskell.TH.Syntax(Exp(AppE, VarE), Q, Type(ConT), dataToExpQ, lift, reportWarning)
+-- |
+-- Module      : Css3.Selector.QuasiQuoters
+-- Description : A module that defines a quasiquoter to parse a string to a css selector.
+-- Maintainer  : hapytexeu+gh@gmail.com
+-- Stability   : experimental
+-- Portability : POSIX
+--
+-- A module that defines a quasiquoter to parse a string to a css selector.
+module Css3.Selector.QuasiQuoters
+  ( csssel,
+    cssselFile,
+    parseCss,
+  )
+where
+
+import Css3.Selector.Core (SelectorGroup, toPattern)
+import Css3.Selector.Lexer (alexScanTokens)
+import Css3.Selector.Parser (cssselector)
+import Data.Data (Data, cast)
+import Data.Text (pack, unpack)
+import Language.Haskell.TH.Quote (QuasiQuoter (QuasiQuoter, quoteDec, quoteExp, quotePat, quoteType), quoteFile)
+import Language.Haskell.TH.Syntax (Exp (AppE, VarE), Q, Type (ConT), dataToExpQ, lift, reportWarning)
 
 -- | Parse the string to a 'SelectorGroup'.
-parseCss :: String -- ^ The string to be parsed to a 'SelectorGroup'
-    -> SelectorGroup -- ^ The selectorgroup that is the equivalent of the given 'String'.
+parseCss ::
+  -- | The string to be parsed to a 'SelectorGroup'
+  String ->
+  -- | The selectorgroup that is the equivalent of the given 'String'.
+  SelectorGroup
 parseCss st = al (alexScanTokens st')
-  where st' = filter ('\r' /=) st
-        al (Left er) = error er
-        al (Right val) = cssselector val
+  where
+    st' = filter ('\r' /=) st
+    al (Left er) = error er
+    al (Right val) = cssselector val
 
 liftDataWithText :: Data a => a -> Q Exp
 liftDataWithText = dataToExpQ ((((AppE (VarE 'pack) <$>) . lift . unpack) <$>) . cast)
@@ -38,12 +42,13 @@ liftDataWithText = dataToExpQ ((((AppE (VarE 'pack) <$>) . lift . unpack) <$>) .
 -- css selector. In case the css selector is invalid. A compiler error will be
 -- thrown (at compile time).
 csssel :: QuasiQuoter
-csssel = QuasiQuoter {
-    quoteExp = liftDataWithText . parseCss,
-    quotePat = pure . toPattern . parseCss,
-    quoteType = const (reportWarning "The type of the quasiquoter will always use the SelectorGroup type." >> pure (ConT ''SelectorGroup)),
-    quoteDec = const (reportWarning "The use of this quasiquoter will not make any declarations." >> pure [])
-  }
+csssel =
+  QuasiQuoter
+    { quoteExp = liftDataWithText . parseCss,
+      quotePat = pure . toPattern . parseCss,
+      quoteType = const (reportWarning "The type of the quasiquoter will always use the SelectorGroup type." >> pure (ConT ''SelectorGroup)),
+      quoteDec = const (reportWarning "The use of this quasiquoter will not make any declarations." >> pure [])
+    }
 
 -- | A quasiquoter that takes the content from the file, and then runs the
 -- content of that file as a 'csssel' quasiquote.
diff --git a/src/Css3/Selector/Utils.hs b/src/Css3/Selector/Utils.hs
index ecacb3b..e3016c2 100644
--- a/src/Css3/Selector/Utils.hs
+++ b/src/Css3/Selector/Utils.hs
@@ -1,36 +1,42 @@
-{-# LANGUAGE CPP, Safe #-}
-
-{-|
-Module      : Css3.Selector.Utils
-Description : A set of utility methods to encode and decode strings.
-Maintainer  : hapytexeu+gh@gmail.com
-Stability   : experimental
-Portability : POSIX
-
-A module to encode and decode css selector strings. These are used in the parser and renderer to parse and render css selector strings.
--}
-module Css3.Selector.Utils (
-    -- * Identifiers
-      readIdentifier, encodeIdentifier
-    , isValidIdentifier, toIdentifier
-    -- * Css strings
-    , readCssString, encodeString, encodeText
-  ) where
-
-import Control.Arrow(first)
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE Safe #-}
+
+-- |
+-- Module      : Css3.Selector.Utils
+-- Description : A set of utility methods to encode and decode strings.
+-- Maintainer  : hapytexeu+gh@gmail.com
+-- Stability   : experimental
+-- Portability : POSIX
+--
+-- A module to encode and decode css selector strings. These are used in the parser and renderer to parse and render css selector strings.
+module Css3.Selector.Utils
+  ( -- * Identifiers
+    readIdentifier,
+    encodeIdentifier,
+    isValidIdentifier,
+    toIdentifier,
 
-import Data.Char(chr, digitToInt, intToDigit, isAsciiLower, isAsciiUpper, isHexDigit, ord)
+    -- * Css strings
+    readCssString,
+    encodeString,
+    encodeText,
+  )
+where
+
+import Control.Arrow (first)
+import Data.Char (chr, digitToInt, intToDigit, isAsciiLower, isAsciiUpper, isHexDigit, ord)
 #if __GLASGOW_HASKELL__ < 803
 import Data.Semigroup((<>))
 #endif
-import Data.Text(Text, cons, pack, singleton, snoc)
+import Data.Text (Text, cons, pack, singleton, snoc)
 import qualified Data.Text as T
 
 _initLast :: [a] -> Maybe ([a], a)
 _initLast [] = Nothing
-_initLast (a:as) = Just (go as a)
-    where go [] x = ([], x)
-          go (y:ys) x = first (x:) (go ys y)
+_initLast (a : as) = Just (go as a)
+  where
+    go [] x = ([], x)
+    go (y : ys) x = first (x :) (go ys y)
 
 _isQuote :: Char -> Bool
 _isQuote '"' = True
@@ -39,27 +45,40 @@ _isQuote _ = False
 
 -- | Parses a css string literal to a string that ontains the content of that
 -- string literal.
-readCssString :: String  -- ^ The string that contains the string literal in the css selector.
-    -> String -- ^ A string that contains the content of the string literal.
-readCssString (c:xs) | _isQuote c = f
-    where f | Just (vs, c') <- _initLast xs = g c' vs
-            | otherwise = "The string literal should contain at least two quotation marks."
-              where  g c' vs | c == c' = _readCssString c vs
-                             | otherwise = "The start and end quotation mark should be the same."
+readCssString ::
+  -- | The string that contains the string literal in the css selector.
+  String ->
+  -- | A string that contains the content of the string literal.
+  String
+readCssString (c : xs) | _isQuote c = f
+  where
+    f
+      | Just (vs, c') <- _initLast xs = g c' vs
+      | otherwise = "The string literal should contain at least two quotation marks."
+      where
+        g c' vs
+          | c == c' = _readCssString c vs
+          | otherwise = "The start and end quotation mark should be the same."
 readCssString _ = error "The string should start with an \" or ' and end with the same quotation."
 
 _readCssString :: Char -> String -> String
 _readCssString c' = go
-    where go [] = []
-          go ('\\':'\n':xs) = go xs
-          go ('\\':ca@(c:xs)) | c == c' = c : go xs
-                              | otherwise = let ~(y,ys) = _parseEscape ca in y : go ys
-          go (x:xs) | x == c' = error "The string can not contain a " ++ show x ++ ", you should escape it."
-                    | otherwise = x : go xs
+  where
+    go [] = []
+    go ('\\' : '\n' : xs) = go xs
+    go ('\\' : ca@(c : xs))
+      | c == c' = c : go xs
+      | otherwise = let ~(y, ys) = _parseEscape ca in y : go ys
+    go (x : xs)
+      | x == c' = error "The string can not contain a " ++ show x ++ ", you should escape it."
+      | otherwise = x : go xs
 
 -- | Parse a given css identifier to the content of the identifier.
-readIdentifier :: String -- ^ The given css identifier to parse.
-    -> String -- ^ The result of the parsing: the content of the identifier.
+readIdentifier ::
+  -- | The given css identifier to parse.
+  String ->
+  -- | The result of the parsing: the content of the identifier.
+  String
 readIdentifier = _readCssString '\\'
 
 _notEncode :: Char -> Bool
@@ -67,56 +86,81 @@ _notEncode x = isAsciiLower x || isAsciiUpper x
 
 -- | Convert a string to a css selector string literal. This is done by putting
 -- quotes around the content, and escaping certain characters.
-encodeString :: Char -- ^ The type of quotes that should be put around the content (should be @'@ or @"@).
-    -> String -- ^ The string that should be converted to a css selector string literal.
-    -> String -- ^ The corresponding css selector string literal.
+encodeString ::
+  -- | The type of quotes that should be put around the content (should be @'@ or @"@).
+  Char ->
+  -- | The string that should be converted to a css selector string literal.
+  String ->
+  -- | The corresponding css selector string literal.
+  String
 encodeString c' = (c' :) . go
-    where go [] = [c']
-          go (c:cs) | _notEncode c = c : go cs
-                    | otherwise = '\\' : _showHex (ord c) (go cs)
+  where
+    go [] = [c']
+    go (c : cs)
+      | _notEncode c = c : go cs
+      | otherwise = '\\' : _showHex (ord c) (go cs)
 
 -- | Convert a string to a css selector string literal. This is done by putting
 -- quotes around the content, and escaping certain characters.
-encodeText :: Char -- ^ The type of quotes that should be put around the content (should be @'@ or @"@).
-    -> Text -- ^ The string that should be converted to a css selector string literal.
-    -> Text -- ^ The corresponding css selector string literal.
+encodeText ::
+  -- | The type of quotes that should be put around the content (should be @'@ or @"@).
+  Char ->
+  -- | The string that should be converted to a css selector string literal.
+  Text ->
+  -- | The corresponding css selector string literal.
+  Text
 encodeText c' t = cons c' (snoc (T.concatMap _encodeCharacter t) c')
 
 _encodeCharacter :: Char -> Text
 _encodeCharacter c
-    | _notEncode c = singleton c
-    | otherwise = cons '\\' (pack (_showHex (ord c) ""))
+  | _notEncode c = singleton c
+  | otherwise = cons '\\' (pack (_showHex (ord c) ""))
 
 -- | Encode a given identifier to its css selector equivalent by escaping
 -- certain characters.
-encodeIdentifier :: Text -- ^ The identifier to encode.
-    -> Text -- ^ The encoded identifier.
+encodeIdentifier ::
+  -- | The identifier to encode.
+  Text ->
+  -- | The encoded identifier.
+  Text
 encodeIdentifier = T.concatMap _encodeCharacter
 
 _showHex :: Int -> ShowS
 _showHex = go (6 :: Int)
-    where go 0 _ s = s
-          go k n rs = go (k-1) q (intToDigit r : rs)
-              where ~(q, r) = quotRem n 16
+  where
+    go 0 _ s = s
+    go k n rs = go (k - 1) q (intToDigit r : rs)
+      where
+        ~(q, r) = quotRem n 16
 
 _parseEscape :: String -> (Char, String)
 _parseEscape = go (6 :: Int) 0
-    where go 0 n cs = yield n cs
-          go _ n "" = yield n ""
-          go i n ca@(c:cs) | isHexDigit c = go (i-1) (16*n+digitToInt c) cs
-                           | otherwise = yield n ca
-          yield n s = (chr n, s)
+  where
+    go 0 n cs = yield n cs
+    go _ n "" = yield n ""
+    go i n ca@(c : cs)
+      | isHexDigit c = go (i - 1) (16 * n + digitToInt c) cs
+      | otherwise = yield n ca
+    yield n s = (chr n, s)
 
 -- | Check if the given identifier is a valid css selector identifier.
-isValidIdentifier :: String  -- ^ The given identifier to check.
-    -> Bool -- ^ 'True' if the given identifier is valid, 'False' otherwise.
+isValidIdentifier ::
+  -- | The given identifier to check.
+  String ->
+  -- | 'True' if the given identifier is valid, 'False' otherwise.
+  Bool
 isValidIdentifier = not . null
 
 -- | Convert the given string to a given object by first checking if it is a
 -- valid identifier, and if not raising an error. If it is a valid identifier,
 -- the string is packed, and wrapped in the given function.
-toIdentifier :: (Text -> a) -- ^ The given function to wrap the 'Text' identifier to an object.
-    -> String -- ^ The string to validate, and wrap into the given function.
-    -> a -- ^ The identifier object to return if the identifier is valid.
-toIdentifier f ident | isValidIdentifier ident = f (pack ident)
-                     | otherwise = error ("The identifier \"" <> show ident <> "\" is not a valid identifier.")
+toIdentifier ::
+  -- | The given function to wrap the 'Text' identifier to an object.
+  (Text -> a) ->
+  -- | The string to validate, and wrap into the given function.
+  String ->
+  -- | The identifier object to return if the identifier is valid.
+  a
+toIdentifier f ident
+  | isValidIdentifier ident = f (pack ident)
+  | otherwise = error ("The identifier \"" <> show ident <> "\" is not a valid identifier.")
diff --git a/stack.yaml b/stack.yaml
index e0c3cd0..02f41bf 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -17,7 +17,7 @@
 #
 # resolver: ./custom-snapshot.yaml
 # resolver: https://example.com/snapshots/2018-01-01.yaml
-resolver: lts-14.10
+resolver: lts-21.1
 save-hackage-creds: false
 
 # User packages to be built.