diff --git a/src/ameba/formatter/disabled_formatter.cr b/src/ameba/formatter/disabled_formatter.cr
index cbe7905b..37865c0f 100644
--- a/src/ameba/formatter/disabled_formatter.cr
+++ b/src/ameba/formatter/disabled_formatter.cr
@@ -6,10 +6,10 @@ module Ameba::Formatter
 
       sources.each do |source|
         source.issues.select(&.disabled?).each do |e|
-          if loc = e.location
-            output << "#{source.path}:#{loc.line_number}".colorize(:cyan)
-            output << " #{e.rule.name}\n"
-          end
+          next unless loc = e.location
+
+          output << "#{source.path}:#{loc.line_number}".colorize(:cyan)
+          output << " #{e.rule.name}\n"
         end
       end
     end
diff --git a/src/ameba/formatter/dot_formatter.cr b/src/ameba/formatter/dot_formatter.cr
index c19bc354..788d9135 100644
--- a/src/ameba/formatter/dot_formatter.cr
+++ b/src/ameba/formatter/dot_formatter.cr
@@ -72,6 +72,7 @@ module Ameba::Formatter
 
     private def finished_in_message(started, finished)
       return unless started && finished
+
       "Finished in #{to_human(finished - started)}".colorize(:default)
     end
 
@@ -92,6 +93,7 @@ module Ameba::Formatter
 
       minutes = span.minutes
       seconds = span.seconds
+
       "#{minutes}:#{seconds < 10 ? "0" : ""}#{seconds} minutes"
     end
 
diff --git a/src/ameba/formatter/explain_formatter.cr b/src/ameba/formatter/explain_formatter.cr
index ebd985a1..a24c5bd1 100644
--- a/src/ameba/formatter/explain_formatter.cr
+++ b/src/ameba/formatter/explain_formatter.cr
@@ -12,19 +12,22 @@ module Ameba::Formatter
     getter output : IO::FileDescriptor | IO::Memory
     getter location : Crystal::Location
 
-    # Creates a new instance of ExplainFormatter.
-    # Accepts *output* which indicates the io where the explanation will be wrtitten to.
+    # Creates a new instance of `ExplainFormatter`.
+    #
+    # Accepts *output* which indicates the io where the explanation will be written to.
     # Second argument is *location* which indicates the location to explain.
     #
     # ```
     # ExplainFormatter.new output,
-    #   {file: path, line: line_number, column: column_number}
+    #   file: path,
+    #   line: line_number,
+    #   column: column_number
     # ```
     def initialize(@output, location)
       @location = Crystal::Location.new(location[:file], location[:line], location[:column])
     end
 
-    # Reports the explainations at the *@location*.
+    # Reports the explanations at the *@location*.
     def finished(sources)
       source = sources.find(&.path.==(@location.filename))
       return unless source
diff --git a/src/ameba/formatter/flycheck_formatter.cr b/src/ameba/formatter/flycheck_formatter.cr
index 63039b82..936bb001 100644
--- a/src/ameba/formatter/flycheck_formatter.cr
+++ b/src/ameba/formatter/flycheck_formatter.cr
@@ -6,12 +6,13 @@ module Ameba::Formatter
       source.issues.each do |e|
         next if e.disabled?
         next if e.correctable? && config[:autocorrect]?
-        if loc = e.location
-          @mutex.synchronize do
-            output.printf "%s:%d:%d: %s: [%s] %s\n",
-              source.path, loc.line_number, loc.column_number, e.rule.severity.symbol,
-              e.rule.name, e.message.gsub('\n', " ")
-          end
+
+        next unless loc = e.location
+
+        @mutex.synchronize do
+          output.printf "%s:%d:%d: %s: [%s] %s\n",
+            source.path, loc.line_number, loc.column_number, e.rule.severity.symbol,
+            e.rule.name, e.message.gsub('\n', " ")
         end
       end
     end
diff --git a/src/ameba/formatter/json_formatter.cr b/src/ameba/formatter/json_formatter.cr
index da16fe1f..6cd3a328 100644
--- a/src/ameba/formatter/json_formatter.cr
+++ b/src/ameba/formatter/json_formatter.cr
@@ -62,7 +62,6 @@ module Ameba::Formatter
   #   },
   # }
   # ```
-  #
   class JSONFormatter < BaseFormatter
     def initialize(@output = STDOUT)
       @result = AsJSON::Result.new
@@ -75,10 +74,17 @@ module Ameba::Formatter
     def source_finished(source : Source)
       json_source = AsJSON::Source.new source.path
 
-      source.issues.each do |e|
-        next if e.disabled?
-        next if e.correctable? && config[:autocorrect]?
-        json_source.issues << AsJSON::Issue.new(e.rule.name, e.rule.severity.to_s, e.location, e.end_location, e.message)
+      source.issues.each do |issue|
+        next if issue.disabled?
+        next if issue.correctable? && config[:autocorrect]?
+
+        json_source.issues << AsJSON::Issue.new(
+          issue.rule.name,
+          issue.rule.severity.to_s,
+          issue.location,
+          issue.end_location,
+          issue.message
+        )
         @result.summary.issues_count += 1
       end
 
@@ -96,7 +102,11 @@ module Ameba::Formatter
       metadata = Metadata.new,
       summary = Summary.new do
       def to_json(json)
-        {sources: sources, metadata: metadata, summary: summary}.to_json(json)
+        {
+          sources:  sources,
+          metadata: metadata,
+          summary:  summary,
+        }.to_json(json)
       end
     end
 
@@ -104,7 +114,10 @@ module Ameba::Formatter
       path : String,
       issues = [] of Issue do
       def to_json(json)
-        {path: path, issues: issues}.to_json(json)
+        {
+          path:   path,
+          issues: issues,
+        }.to_json(json)
       end
     end
 
@@ -115,15 +128,19 @@ module Ameba::Formatter
       end_location : Crystal::Location?,
       message : String do
       def to_json(json)
-        json.object do
-          json.field :rule_name, rule_name
-          json.field :severity, severity
-          json.field :message, message
-          json.field :location,
-            {line: location.try &.line_number, column: location.try &.column_number}
-          json.field :end_location,
-            {line: end_location.try &.line_number, column: end_location.try &.column_number}
-        end
+        {
+          rule_name: rule_name,
+          severity:  severity,
+          message:   message,
+          location:  {
+            line:   location.try &.line_number,
+            column: location.try &.column_number,
+          },
+          end_location: {
+            line:   end_location.try &.line_number,
+            column: end_location.try &.column_number,
+          },
+        }.to_json(json)
       end
     end
 
@@ -131,10 +148,10 @@ module Ameba::Formatter
       ameba_version : String = Ameba::VERSION,
       crystal_version : String = Crystal::VERSION do
       def to_json(json)
-        json.object do
-          json.field :ameba_version, ameba_version
-          json.field :crystal_version, crystal_version
-        end
+        {
+          ameba_version:   ameba_version,
+          crystal_version: crystal_version,
+        }.to_json(json)
       end
     end
 
@@ -143,10 +160,10 @@ module Ameba::Formatter
       property issues_count = 0
 
       def to_json(json)
-        json.object do
-          json.field :target_sources_count, target_sources_count
-          json.field :issues_count, issues_count
-        end
+        {
+          target_sources_count: target_sources_count,
+          issues_count:         issues_count,
+        }.to_json(json)
       end
     end
   end
diff --git a/src/ameba/formatter/todo_formatter.cr b/src/ameba/formatter/todo_formatter.cr
index 8c8524f9..eaee9efc 100644
--- a/src/ameba/formatter/todo_formatter.cr
+++ b/src/ameba/formatter/todo_formatter.cr
@@ -20,9 +20,9 @@ module Ameba::Formatter
         return
       end
 
-      file = generate_todo_config issues
-      @output.puts "Created #{file.path}"
-      file
+      generate_todo_config(issues).tap do |file|
+        @output.puts "Created #{file.path}"
+      end
     end
 
     private def generate_todo_config(issues)
@@ -43,6 +43,7 @@ module Ameba::Formatter
         issues.each do |issue|
           next if issue.disabled? || issue.rule.is_a?(Rule::Lint::Syntax)
           next if issue.correctable? && config[:autocorrect]?
+
           (h[issue.rule] ||= Array(Issue).new) << issue
         end
       end
diff --git a/src/ameba/rule/style/guard_clause.cr b/src/ameba/rule/style/guard_clause.cr
index 4689f6e9..618c4c36 100644
--- a/src/ameba/rule/style/guard_clause.cr
+++ b/src/ameba/rule/style/guard_clause.cr
@@ -160,7 +160,7 @@ module Ameba::Rule::Style
     end
 
     private def guard_clause(node)
-      node = node.right if node.is_a?(Crystal::And) || node.is_a?(Crystal::Or)
+      node = node.right if node.is_a?(Crystal::BinaryOp)
 
       return unless location = node.location
       return unless end_location = node.end_location
@@ -175,11 +175,9 @@ module Ameba::Rule::Style
     end
 
     def guard_clause_source(source, guard_clause, parent)
-      if parent.is_a?(Crystal::And) || parent.is_a?(Crystal::Or)
-        node_source(parent, source.lines)
-      else
-        node_source(guard_clause, source.lines)
-      end
+      node = parent.is_a?(Crystal::BinaryOp) ? parent : guard_clause
+
+      node_source(node, source.lines)
     end
   end
 end
diff --git a/src/ameba/rule/style/redundant_begin.cr b/src/ameba/rule/style/redundant_begin.cr
index 1a5a7101..be21d73d 100644
--- a/src/ameba/rule/style/redundant_begin.cr
+++ b/src/ameba/rule/style/redundant_begin.cr
@@ -80,8 +80,8 @@ module Ameba::Rule::Style
 
       begin_loc, end_loc = begin_range
       begin_loc, end_loc = def_loc.seek(begin_loc), def_loc.seek(end_loc)
-      begin_end_loc = begin_loc.adjust(column_number: {{"begin".size - 1}})
-      end_end_loc = end_loc.adjust(column_number: {{"end".size - 1}})
+      begin_end_loc = begin_loc.adjust(column_number: {{ "begin".size - 1 }})
+      end_end_loc = end_loc.adjust(column_number: {{ "end".size - 1 }})
 
       issue_for begin_loc, begin_end_loc, MSG do |corrector|
         corrector.remove(begin_loc, begin_end_loc)
diff --git a/src/ameba/rule/style/verbose_block.cr b/src/ameba/rule/style/verbose_block.cr
index e7e4bcdd..a97661cb 100644
--- a/src/ameba/rule/style/verbose_block.cr
+++ b/src/ameba/rule/style/verbose_block.cr
@@ -62,10 +62,7 @@ module Ameba::Rule::Style
     end
 
     protected def operator?(name)
-      name.each_char do |char|
-        return false unless char.in?(OPERATOR_CHARS)
-      end
-      !name.empty?
+      !name.empty? && name[0].in?(OPERATOR_CHARS)
     end
 
     protected def setter?(name)
diff --git a/src/ameba/runner.cr b/src/ameba/runner.cr
index fb709464..a987db12 100644
--- a/src/ameba/runner.cr
+++ b/src/ameba/runner.cr
@@ -9,7 +9,6 @@ module Ameba
   # runner = Ameba::Runner.new config
   # runner.run.success? # => true or false
   # ```
-  #
   class Runner
     # An error indicating that the inspection loop got stuck correcting
     # issues back and forth.