diff --git a/src/CSSList/CSSList.php b/src/CSSList/CSSList.php
index 1267af29..6f31def8 100644
--- a/src/CSSList/CSSList.php
+++ b/src/CSSList/CSSList.php
@@ -167,9 +167,12 @@ private static function parseAtRule(ParserState $oParserState)
             $sMediaQuery = null;
             if (!$oParserState->comes(';')) {
                 $sMediaQuery = \trim($oParserState->consumeUntil([';', ParserState::EOF]));
+                if ($sMediaQuery === '') {
+                    $sMediaQuery = null;
+                }
             }
             $oParserState->consumeUntil([';', ParserState::EOF], true, true);
-            return new Import($oLocation, $sMediaQuery ?: null, $iIdentifierLineNum);
+            return new Import($oLocation, $sMediaQuery, $iIdentifierLineNum);
         } elseif ($sIdentifier === 'charset') {
             $oCharsetString = CSSString::parse($oParserState);
             $oParserState->consumeWhiteSpace();
@@ -240,9 +243,8 @@ private static function parseAtRule(ParserState $oParserState)
      * We need to check for these versions too.
      *
      * @param string $sIdentifier
-     * @param string $sMatch
      */
-    private static function identifierIs($sIdentifier, $sMatch): bool
+    private static function identifierIs($sIdentifier, string $sMatch): bool
     {
         return (\strcasecmp($sIdentifier, $sMatch) === 0)
             ?: \preg_match("/^(-\\w+-)?$sMatch$/i", $sIdentifier) === 1;
diff --git a/src/OutputFormat.php b/src/OutputFormat.php
index 2b5607db..3f126346 100644
--- a/src/OutputFormat.php
+++ b/src/OutputFormat.php
@@ -223,14 +223,13 @@ public function set($aNames, $mValue)
     }
 
     /**
-     * @param string $sMethodName
      * @param array<array-key, mixed> $aArguments
      *
      * @return mixed
      *
      * @throws \Exception
      */
-    public function __call($sMethodName, array $aArguments)
+    public function __call(string $sMethodName, array $aArguments)
     {
         if (\strpos($sMethodName, 'set') === 0) {
             return $this->set(\substr($sMethodName, 3), $aArguments[0]);
@@ -303,17 +302,15 @@ public function level()
     /**
      * Creates an instance of this class without any particular formatting settings.
      */
-    public static function create(): OutputFormat
+    public static function create(): self
     {
         return new OutputFormat();
     }
 
     /**
      * Creates an instance of this class with a preset for compact formatting.
-     *
-     * @return self
      */
-    public static function createCompact()
+    public static function createCompact(): self
     {
         $format = self::create();
         $format->set('Space*Rules', '')
@@ -327,10 +324,8 @@ public static function createCompact()
 
     /**
      * Creates an instance of this class with a preset for pretty formatting.
-     *
-     * @return self
      */
-    public static function createPretty()
+    public static function createPretty(): self
     {
         $format = self::create();
         $format->set('Space*Rules', "\n")
diff --git a/src/OutputFormatter.php b/src/OutputFormatter.php
index 4349f664..6e68037f 100644
--- a/src/OutputFormatter.php
+++ b/src/OutputFormatter.php
@@ -132,11 +132,10 @@ public function safely($cCode)
     /**
      * Clone of the `implode` function, but calls `render` with the current output format instead of `__toString()`.
      *
-     * @param string $sSeparator
      * @param array<array-key, Renderable|string> $aValues
      * @param bool $bIncreaseLevel
      */
-    public function implode($sSeparator, array $aValues, $bIncreaseLevel = false): string
+    public function implode(string $sSeparator, array $aValues, $bIncreaseLevel = false): string
     {
         $sResult = '';
         $oFormat = $this->oFormat;
diff --git a/src/Parsing/Anchor.php b/src/Parsing/Anchor.php
index 1a1d42ae..545cb035 100644
--- a/src/Parsing/Anchor.php
+++ b/src/Parsing/Anchor.php
@@ -15,13 +15,12 @@ class Anchor
     private $iPosition;
 
     /**
-     * @var \Sabberworm\CSS\Parsing\ParserState
+     * @var ParserState
      */
     private $oParserState;
 
     /**
      * @param int $iPosition
-     * @param \Sabberworm\CSS\Parsing\ParserState $oParserState
      */
     public function __construct($iPosition, ParserState $oParserState)
     {
diff --git a/src/Parsing/ParserState.php b/src/Parsing/ParserState.php
index fa146d7e..22152fbd 100644
--- a/src/Parsing/ParserState.php
+++ b/src/Parsing/ParserState.php
@@ -362,12 +362,10 @@ public function isEnd(): bool
      * @param string $consumeEnd
      * @param array<int, Comment> $comments
      *
-     * @return string
-     *
      * @throws UnexpectedEOFException
      * @throws UnexpectedTokenException
      */
-    public function consumeUntil($aEnd, $bIncludeEnd = false, $consumeEnd = false, array &$comments = [])
+    public function consumeUntil($aEnd, $bIncludeEnd = false, $consumeEnd = false, array &$comments = []): string
     {
         $aEnd = \is_array($aEnd) ? $aEnd : [$aEnd];
         $out = '';
diff --git a/src/RuleSet/RuleSet.php b/src/RuleSet/RuleSet.php
index c2fd6e30..e53abd52 100644
--- a/src/RuleSet/RuleSet.php
+++ b/src/RuleSet/RuleSet.php
@@ -82,7 +82,7 @@ public static function parseRuleSet(ParserState $oParserState, RuleSet $oRuleSet
             } else {
                 $oRule = Rule::parse($oParserState);
             }
-            if ($oRule) {
+            if ($oRule instanceof Rule) {
                 $oRuleSet->addRule($oRule);
             }
         }
diff --git a/src/Settings.php b/src/Settings.php
index b5934a05..17e5fa00 100644
--- a/src/Settings.php
+++ b/src/Settings.php
@@ -56,9 +56,9 @@ public static function create(): Settings
      *
      * @param bool $bMultibyteSupport
      *
-     * @return self fluent interface
+     * @return $this fluent interface
      */
-    public function withMultibyteSupport($bMultibyteSupport = true)
+    public function withMultibyteSupport($bMultibyteSupport = true): self
     {
         $this->bMultibyteSupport = $bMultibyteSupport;
         return $this;
@@ -69,9 +69,9 @@ public function withMultibyteSupport($bMultibyteSupport = true)
      *
      * @param string $sDefaultCharset
      *
-     * @return self fluent interface
+     * @return $this fluent interface
      */
-    public function withDefaultCharset($sDefaultCharset)
+    public function withDefaultCharset($sDefaultCharset): self
     {
         $this->sDefaultCharset = $sDefaultCharset;
         return $this;
@@ -82,9 +82,9 @@ public function withDefaultCharset($sDefaultCharset)
      *
      * @param bool $bLenientParsing
      *
-     * @return self fluent interface
+     * @return $this fluent interface
      */
-    public function withLenientParsing($bLenientParsing = true)
+    public function withLenientParsing($bLenientParsing = true): self
     {
         $this->bLenientParsing = $bLenientParsing;
         return $this;
@@ -93,9 +93,9 @@ public function withLenientParsing($bLenientParsing = true)
     /**
      * Configures the parser to choke on invalid rules.
      *
-     * @return self fluent interface
+     * @return $this fluent interface
      */
-    public function beStrict()
+    public function beStrict(): self
     {
         return $this->withLenientParsing(false);
     }
diff --git a/src/Value/CSSFunction.php b/src/Value/CSSFunction.php
index 5902cf77..82b21e8a 100644
--- a/src/Value/CSSFunction.php
+++ b/src/Value/CSSFunction.php
@@ -103,10 +103,7 @@ public function __toString(): string
         return $this->render(new OutputFormat());
     }
 
-    /**
-     * @return string
-     */
-    public function render(OutputFormat $oOutputFormat)
+    public function render(OutputFormat $oOutputFormat): string
     {
         $aArguments = parent::render($oOutputFormat);
         return "{$this->sName}({$aArguments})";
diff --git a/src/Value/CSSString.php b/src/Value/CSSString.php
index 3385f48c..f212bdd8 100644
--- a/src/Value/CSSString.php
+++ b/src/Value/CSSString.php
@@ -53,7 +53,7 @@ public static function parse(ParserState $oParserState): CSSString
         $sContent = null;
         if ($sQuote === null) {
             // Unquoted strings end in whitespace or with braces, brackets, parentheses
-            while (!\preg_match('/[\\s{}()<>\\[\\]]/isu', $oParserState->peek())) {
+            while (\preg_match('/[\\s{}()<>\\[\\]]/isu', $oParserState->peek()) !== 1) {
                 $sResult .= $oParserState->parseCharacter(false);
             }
         } else {
diff --git a/src/Value/Color.php b/src/Value/Color.php
index 706d1d1f..55a6ce3d 100644
--- a/src/Value/Color.php
+++ b/src/Value/Color.php
@@ -103,15 +103,9 @@ public static function parse(ParserState $oParserState, bool $bIgnoreCase = fals
     }
 
     /**
-     * @param float $fVal
-     * @param float $fFromMin
-     * @param float $fFromMax
-     * @param float $fToMin
-     * @param float $fToMax
-     *
      * @return float
      */
-    private static function mapRange($fVal, $fFromMin, $fFromMax, $fToMin, $fToMax)
+    private static function mapRange(float $fVal, float $fFromMin, float $fFromMax, float $fToMin, float $fToMax)
     {
         $fFromRange = $fFromMax - $fFromMin;
         $fToRange = $fToMax - $fToMin;
@@ -151,10 +145,7 @@ public function __toString(): string
         return $this->render(new OutputFormat());
     }
 
-    /**
-     * @return string
-     */
-    public function render(OutputFormat $oOutputFormat)
+    public function render(OutputFormat $oOutputFormat): string
     {
         // Shorthand RGB color values
         if ($oOutputFormat->getRGBHashNotation() && \implode('', \array_keys($this->aComponents)) === 'rgb') {