diff --git a/src/mechanize/form.cr b/src/mechanize/form.cr
index f3a8606..fc5e254 100644
--- a/src/mechanize/form.cr
+++ b/src/mechanize/form.cr
@@ -8,197 +8,199 @@ require "./form/button"
 require "./form/select_list"
 require "./utils/element_matcher"
 
-# This class represents the form tag of html.
-class Mechanize::Form
-  include Mechanize::ElementMatcher
+class Mechanize
+  # This class represents the form tag of html.
+  class Form
+    include ElementMatcher
 
-  getter node : Node | Lexbor::Node
-  # returns hoge array of `Mechanize::FormContent::Field` in the form.
-  getter fields : Array(FormContent::Field)
-  # returns an array of input tags whose type is checkbox in the form.
-  getter checkboxes : Array(FormContent::CheckBox)
-  # returns an array of input tags whose type is radio in the form.
-  getter radiobuttons : Array(FormContent::RadioButton)
-  # returns an array of input tags whose type is select in the form.
-  getter selectboxes : Array(FormContent::MultiSelectList)
-  # returns an array of button tags and input tag whose type is button,submit,reset,image.
-  getter buttons : Array(FormContent::Button)
-  # returns form's 'enctype' attribute.
-  getter enctype : String
-  # returns form's 'method' attribute.
-  getter method : String
-  # returns form's 'name' attribute.
-  getter name : String
-  # return form's 'action' attribute.
-  property action : String
-  # returns the page which includes the form.
-  getter page : Mechanize::Page?
+    getter node : Node | Lexbor::Node
+    # returns hoge array of `Mechanize::FormContent::Field` in the form.
+    getter fields : Array(FormContent::Field)
+    # returns an array of input tags whose type is checkbox in the form.
+    getter checkboxes : Array(FormContent::CheckBox)
+    # returns an array of input tags whose type is radio in the form.
+    getter radiobuttons : Array(FormContent::RadioButton)
+    # returns an array of input tags whose type is select in the form.
+    getter selectboxes : Array(FormContent::MultiSelectList)
+    # returns an array of button tags and input tag whose type is button,submit,reset,image.
+    getter buttons : Array(FormContent::Button)
+    # returns form's 'enctype' attribute.
+    getter enctype : String
+    # returns form's 'method' attribute.
+    getter method : String
+    # returns form's 'name' attribute.
+    getter name : String
+    # return form's 'action' attribute.
+    property action : String
+    # returns the page which includes the form.
+    getter page : Page?
 
-  def initialize(node : Node | Lexbor::Node, page : Mechanize::Page? = nil)
-    @enctype = node.fetch("enctype", "application/x-www-form-urlencoded")
-    @node = node
-    @fields = Array(Mechanize::FormContent::Field).new
-    @checkboxes = Array(Mechanize::FormContent::CheckBox).new
-    @radiobuttons = Array(Mechanize::FormContent::RadioButton).new
-    @selectboxes = Array(Mechanize::FormContent::MultiSelectList).new
-    @buttons = Array(Mechanize::FormContent::Button).new
-    @action = node.fetch("action", "")
-    @method = node.fetch("method", "GET").upcase
-    @name = node.fetch("name", "")
-    @clicked_buttons = Array(Mechanize::FormContent::Button).new
-    @page = page
-    # @mech             = mech
+    def initialize(node : Node | Lexbor::Node, page : Page? = nil)
+      @enctype = node.fetch("enctype", "application/x-www-form-urlencoded")
+      @node = node
+      @fields = Array(FormContent::Field).new
+      @checkboxes = Array(FormContent::CheckBox).new
+      @radiobuttons = Array(FormContent::RadioButton).new
+      @selectboxes = Array(FormContent::MultiSelectList).new
+      @buttons = Array(FormContent::Button).new
+      @action = node.fetch("action", "")
+      @method = node.fetch("method", "GET").upcase
+      @name = node.fetch("name", "")
+      @clicked_buttons = Array(FormContent::Button).new
+      @page = page
+      # @mech             = mech
 
-    # @encoding = node['accept-charset'] || (page && page.encoding) || nil
-    # @ignore_encoding_error = false
-    parse
-  end
+      # @encoding = node['accept-charset'] || (page && page.encoding) || nil
+      # @ignore_encoding_error = false
+      parse
+    end
 
-  def request_data
-    query_params = build_query
-    build_query_string(query_params)
-  end
+    def request_data
+      query_params = build_query
+      build_query_string(query_params)
+    end
 
-  # generate fields_with and field_with methods.
-  # These methods are used for finding nodes that matches conditions.
-  # ex.) field_with("email") finds <input name="email">
+    # generate fields_with and field_with methods.
+    # These methods are used for finding nodes that matches conditions.
+    # ex.) field_with("email") finds <input name="email">
 
-  elements_with "field"
-  elements_with "radiobutton"
-  elements_with "checkbox", "checkboxes"
-  elements_with "button"
+    elements_with "field"
+    elements_with "radiobutton"
+    elements_with "checkbox", "checkboxes"
+    elements_with "button"
 
-  # Returns all fields of <input type="textarea">
-  def textareas
-    fields.select { |f| f.class == FormContent::Textarea }.map &.as(FormContent::Textarea)
-  end
+    # Returns all fields of &lt;input type="textarea"&gt;
+    def textareas
+      fields.select { |f| f.class == FormContent::Textarea }.map &.as(FormContent::Textarea)
+    end
 
-  private def parse
-    @node.css("input").not_nil!.each do |html_node|
-      html_node = html_node.as(Lexbor::Node)
-      type = (html_node["type"]? || "text").downcase
-      case type
-      when "checkbox"
-        checkboxes << Mechanize::FormContent::CheckBox.new(html_node, self)
-      when "radio"
-        radiobuttons << Mechanize::FormContent::RadioButton.new(html_node, self)
-      when "button"
-        buttons << Mechanize::FormContent::Button.new(html_node, @node)
-      when "submit"
-        buttons << Mechanize::FormContent::SubmitButton.new(html_node, @node)
-      when "reset"
-        buttons << Mechanize::FormContent::ResetButton.new(html_node, @node)
-      when "image"
-        buttons << Mechanize::FormContent::ImageButton.new(html_node, @node)
-      when "text"
-        fields << Mechanize::FormContent::Text.new(html_node)
-      when "hidden"
-        fields << Mechanize::FormContent::Hidden.new(html_node)
-      when "textarea"
-        fields << Mechanize::FormContent::Textarea.new(html_node)
-      else
-        fields << Mechanize::FormContent::Field.new(html_node)
+    private def parse
+      @node.css("input").not_nil!.each do |html_node|
+        html_node = html_node.as(Lexbor::Node)
+        type = (html_node["type"]? || "text").downcase
+        case type
+        when "checkbox"
+          checkboxes << FormContent::CheckBox.new(html_node, self)
+        when "radio"
+          radiobuttons << FormContent::RadioButton.new(html_node, self)
+        when "button"
+          buttons << FormContent::Button.new(html_node, @node)
+        when "submit"
+          buttons << FormContent::SubmitButton.new(html_node, @node)
+        when "reset"
+          buttons << FormContent::ResetButton.new(html_node, @node)
+        when "image"
+          buttons << FormContent::ImageButton.new(html_node, @node)
+        when "text"
+          fields << FormContent::Text.new(html_node)
+        when "hidden"
+          fields << FormContent::Hidden.new(html_node)
+        when "textarea"
+          fields << FormContent::Textarea.new(html_node)
+        else
+          fields << FormContent::Field.new(html_node)
+        end
       end
-    end
 
-    # Find all textarea tags
-    @node.css("textarea").each do |node|
-      node = node.as(Lexbor::Node)
-      next if node["name"].empty?
-      @fields << FormContent::Textarea.new(node, node.inner_text)
-    end
-
-    @node.css("button").each do |node|
-      node = node.as(Lexbor::Node)
-      type = node.fetch("type", "submit").downcase
-      next if type == "reset"
-      @buttons << FormContent::Button.new(node, @node)
-    end
-
-    # Find all select tags
-    @node.css("select").each do |node|
-      node = node.as(Lexbor::Node)
-      next if node["name"].empty?
-      if node.has_key?("multiple")
-        @selectboxes << FormContent::MultiSelectList.new(node)
-      else
-        @selectboxes << FormContent::SelectList.new(node)
+      # Find all textarea tags
+      @node.css("textarea").each do |node|
+        node = node.as(Lexbor::Node)
+        next if node["name"].empty?
+        @fields << FormContent::Textarea.new(node, node.inner_text)
       end
-    end
-  end
 
-  private def build_query_string(params : Array(Array(String)))
-    params.reduce("") do |acc, arr|
-      hash = {arr[0] => arr[1]}
-      acc + URI::Params.encode(hash) + '&'
-    end.rchop
-  end
-
-  private def build_query
-    query = [] of Array(String)
-    successful_controls = Array(FormContent::Field | FormContent::CheckBox).new
-    fields.each do |elm|
-      successful_controls << elm
-    end
-    checkboxes.each do |elm|
-      if elm.checked
-        successful_controls << elm
+      @node.css("button").each do |node|
+        node = node.as(Lexbor::Node)
+        type = node.fetch("type", "submit").downcase
+        next if type == "reset"
+        @buttons << FormContent::Button.new(node, @node)
       end
-    end
-    radio_groups = Hash(String, Array(FormContent::RadioButton)).new
-    radiobuttons.each do |radio|
-      name = radio.name
-      radio_groups[name] = Array(FormContent::RadioButton).new unless radio_groups.has_key?(name)
-      radio_groups[name] << radio
-    end
 
-    radio_groups.each_value do |g|
-      checked = g.select(&.checked)
-      if checked.uniq.size > 1
-        # values = checked.map(&.value).join(', ').inspect
-        # name = checked.first.name.inspect
-        # raise Mechanize::Error,
-        #      "radiobuttons #{values} are checked in the #{name} group, " \
-        #      "only one is allowed"
-        raise Mechanize::Error.new
-      else
-        successful_controls << checked.first unless checked.empty?
-      end
-    end
-
-    @clicked_buttons.each do |b|
-      successful_controls << b
-    end
-
-    successful_controls.each do |ctrl|
-      value = ctrl.query_value
-      next if value[0] == ""
-      query.push(value)
-    end
-
-    @selectboxes.each do |s|
-      value = s.query_value
-      if value
-        value.each do |v|
-          query.push(v)
+      # Find all select tags
+      @node.css("select").each do |node|
+        node = node.as(Lexbor::Node)
+        next if node["name"].empty?
+        if node.has_key?("multiple")
+          @selectboxes << FormContent::MultiSelectList.new(node)
+        else
+          @selectboxes << FormContent::SelectList.new(node)
         end
       end
     end
 
-    query
-  end
-
-  # This method adds a button to the query.  If the form needs to be
-  # submitted with multiple buttons, pass each button to this method.
-  def add_button_to_query(button)
-    unless button.form_node == @node
-      message = ""
-      "#{button.inspect} does not belong to the same page as " \
-      "the form #{@name.inspect} in #{@page.try &.uri}"
-      message = "not a valid button"
-      raise ArgumentError.new(message)
+    private def build_query_string(params : Array(Array(String)))
+      params.reduce("") do |acc, arr|
+        hash = {arr[0] => arr[1]}
+        acc + URI::Params.encode(hash) + '&'
+      end.rchop
     end
 
-    @clicked_buttons << button
+    private def build_query
+      query = [] of Array(String)
+      successful_controls = Array(FormContent::Field | FormContent::CheckBox).new
+      fields.each do |elm|
+        successful_controls << elm
+      end
+      checkboxes.each do |elm|
+        if elm.checked
+          successful_controls << elm
+        end
+      end
+      radio_groups = Hash(String, Array(FormContent::RadioButton)).new
+      radiobuttons.each do |radio|
+        name = radio.name
+        radio_groups[name] = Array(FormContent::RadioButton).new unless radio_groups.has_key?(name)
+        radio_groups[name] << radio
+      end
+
+      radio_groups.each_value do |g|
+        checked = g.select(&.checked)
+        if checked.uniq.size > 1
+          # values = checked.map(&.value).join(', ').inspect
+          # name = checked.first.name.inspect
+          # raise Mechanize::Error,
+          #      "radiobuttons #{values} are checked in the #{name} group, " \
+          #      "only one is allowed"
+          raise Error.new
+        else
+          successful_controls << checked.first unless checked.empty?
+        end
+      end
+
+      @clicked_buttons.each do |b|
+        successful_controls << b
+      end
+
+      successful_controls.each do |ctrl|
+        value = ctrl.query_value
+        next if value[0] == ""
+        query.push(value)
+      end
+
+      @selectboxes.each do |s|
+        value = s.query_value
+        if value
+          value.each do |v|
+            query.push(v)
+          end
+        end
+      end
+
+      query
+    end
+
+    # This method adds a button to the query.  If the form needs to be
+    # submitted with multiple buttons, pass each button to this method.
+    def add_button_to_query(button)
+      unless button.form_node == @node
+        message = ""
+        "#{button.inspect} does not belong to the same page as " \
+        "the form #{@name.inspect} in #{@page.try &.uri}"
+        message = "not a valid button"
+        raise ArgumentError.new(message)
+      end
+
+      @clicked_buttons << button
+    end
   end
 end
diff --git a/src/mechanize/form/button.cr b/src/mechanize/form/button.cr
index 4a55eda..dab59f5 100644
--- a/src/mechanize/form/button.cr
+++ b/src/mechanize/form/button.cr
@@ -1,5 +1,5 @@
 # This class represents button related html element.
-# <button>, and <input> whose type is button, reset, image, submit.
+# &lt;button&gt;, and &lt;input&gt; whose type is button, reset, image, submit.
 class Mechanize::FormContent::Button < Mechanize::FormContent::Field
   getter form_node : Node | Lexbor::Node
 
diff --git a/src/mechanize/form/check_box.cr b/src/mechanize/form/check_box.cr
index b239cbf..c2f6476 100644
--- a/src/mechanize/form/check_box.cr
+++ b/src/mechanize/form/check_box.cr
@@ -1,4 +1,4 @@
-# This class represents <input type="checkbox">
+# This class represents &lt;input type="checkbox"&gt;
 class Mechanize::FormContent::CheckBox < Mechanize::FormContent::RadioButton
   # set checkbox checked
   def check
diff --git a/src/mechanize/form/field.cr b/src/mechanize/form/field.cr
index f98ffee..62166d9 100644
--- a/src/mechanize/form/field.cr
+++ b/src/mechanize/form/field.cr
@@ -1,4 +1,4 @@
-# This class represents <input> elements in the form.
+# This class represents &lt;input&gt; elements in the form.
 class Mechanize::FormContent::Field
   # returns field's 'value' attribute
   property value : String?
diff --git a/src/mechanize/form/hidden.cr b/src/mechanize/form/hidden.cr
index 59557f6..10e8222 100644
--- a/src/mechanize/form/hidden.cr
+++ b/src/mechanize/form/hidden.cr
@@ -1,3 +1,3 @@
-# This class represents <input type="hidden">
+# This class represents &lt;input type="hidden"&gt;
 class Mechanize::FormContent::Hidden < Mechanize::FormContent::Field
 end
diff --git a/src/mechanize/form/image_button.cr b/src/mechanize/form/image_button.cr
index 583f39d..272633b 100644
--- a/src/mechanize/form/image_button.cr
+++ b/src/mechanize/form/image_button.cr
@@ -1,3 +1,3 @@
-# This class represents <input type="image">
+# This class represents &lt;input type="image"&gt;
 class Mechanize::FormContent::ImageButton < Mechanize::FormContent::Button
 end
diff --git a/src/mechanize/form/multi_select_list.cr b/src/mechanize/form/multi_select_list.cr
index a960c72..781b805 100644
--- a/src/mechanize/form/multi_select_list.cr
+++ b/src/mechanize/form/multi_select_list.cr
@@ -1,6 +1,6 @@
 require "./option"
 
-# This class represents <select multiple>
+# This class represents &lt;select multiple&gt;
 class Mechanize::FormContent::MultiSelectList
   getter node : Lexbor::Node
   getter name : String
diff --git a/src/mechanize/form/option.cr b/src/mechanize/form/option.cr
index ad5d4e5..d7d641f 100644
--- a/src/mechanize/form/option.cr
+++ b/src/mechanize/form/option.cr
@@ -1,3 +1,4 @@
+# This class represents &lt;option&gt; of &lt;select&gt;
 class Mechanize::FormContent::Option
   getter select_list : FormContent::MultiSelectList
   getter node : Lexbor::Node
diff --git a/src/mechanize/form/radio_button.cr b/src/mechanize/form/radio_button.cr
index b37aab5..efb0b48 100644
--- a/src/mechanize/form/radio_button.cr
+++ b/src/mechanize/form/radio_button.cr
@@ -1,4 +1,4 @@
-# This class represents <input type="radio">
+# This class represents &lt;input type="radio"&gt;
 class Mechanize::FormContent::RadioButton < Mechanize::FormContent::Field
   property :checked, :form
 
diff --git a/src/mechanize/form/reset_button.cr b/src/mechanize/form/reset_button.cr
index a5385e7..1905131 100644
--- a/src/mechanize/form/reset_button.cr
+++ b/src/mechanize/form/reset_button.cr
@@ -1,3 +1,3 @@
-# This class represents <input type="reset">
+# This class represents &lt;input type="reset"&gt;
 class Mechanize::FormContent::ResetButton < Mechanize::FormContent::Button
 end
diff --git a/src/mechanize/form/select_list.cr b/src/mechanize/form/select_list.cr
index 4670e08..9ce252d 100644
--- a/src/mechanize/form/select_list.cr
+++ b/src/mechanize/form/select_list.cr
@@ -1,6 +1,6 @@
 require "./multi_select_list"
 
-# This class represents <select> which is not multiple
+# This class represents &lt;select&gt; which is not multiple
 class Mechanize::FormContent::SelectList < Mechanize::FormContent::MultiSelectList
   def initialize(node)
     super node
diff --git a/src/mechanize/form/submit_button.cr b/src/mechanize/form/submit_button.cr
index 90aa146..0a67b97 100644
--- a/src/mechanize/form/submit_button.cr
+++ b/src/mechanize/form/submit_button.cr
@@ -1,3 +1,3 @@
-# This class represents <input type="submit">
+# This class represents &lt;input type="submit"&gt;
 class Mechanize::FormContent::SubmitButton < Mechanize::FormContent::Button
 end
diff --git a/src/mechanize/form/text.cr b/src/mechanize/form/text.cr
index e39fd47..8dffbd1 100644
--- a/src/mechanize/form/text.cr
+++ b/src/mechanize/form/text.cr
@@ -1,3 +1,3 @@
-# This class represents <input type="text">
+# This class represents &lt;input type="text"&gt;
 class Mechanize::FormContent::Text < Mechanize::FormContent::Field
 end
diff --git a/src/mechanize/form/textarea.cr b/src/mechanize/form/textarea.cr
index 39a4094..47b53d8 100644
--- a/src/mechanize/form/textarea.cr
+++ b/src/mechanize/form/textarea.cr
@@ -1,3 +1,3 @@
-# This class represents <input type="textarea">
+# This class represents &lt;input type="textarea"&gt;
 class Mechanize::FormContent::Textarea < Mechanize::FormContent::Field
 end
diff --git a/src/mechanize/history.cr b/src/mechanize/history.cr
index 5448079..d729640 100644
--- a/src/mechanize/history.cr
+++ b/src/mechanize/history.cr
@@ -1,17 +1,17 @@
 require "./page"
 
-# This class represents the history of http response you sent.
-# If you send a request, mechanize saves the history.
 class Mechanize
+  # This class represents the history of http response you sent.
+  # If you send a request, mechanize saves the history.
   class History
     # max page size history can save. default is 100.
     # as same as `agent.max_history`.
     property max_size : Int32
-    property array : Array(Mechanize::Page)
+    property array : Array(Page)
 
     delegate :size, :empty?, :last, to: array
 
-    def initialize(max_size = 100, array = Array(Mechanize::Page).new)
+    def initialize(max_size = 100, array = Array(Page).new)
       @max_size = max_size
       @array = array
     end
diff --git a/src/mechanize/http/agent.cr b/src/mechanize/http/agent.cr
index 86f9236..1cb1458 100644
--- a/src/mechanize/http/agent.cr
+++ b/src/mechanize/http/agent.cr
@@ -5,15 +5,16 @@ require "../history"
 
 class Mechanize
   module HTTP
+    # This class handles web interation mechanize made.
     class Agent
       property request_headers : ::HTTP::Headers
       property context : Mechanize?
-      property history : Mechanize::History
+      property history : History
       property user_agent : String
       property request_cookies : ::HTTP::Cookies
 
       def initialize(@context : Mechanize? = nil)
-        @history = Mechanize::History.new
+        @history = History.new
         @request_headers = ::HTTP::Headers.new
         @context = context
         @request_cookies = ::HTTP::Cookies.new
@@ -72,7 +73,7 @@ class Mechanize
       # ```
       # agent.current_page
       # ```
-      def current_page : Mechanize::Page
+      def current_page : Page
         @history.last
       end
 
@@ -80,7 +81,7 @@ class Mechanize
       # ```
       # agent.back
       # ```
-      def back : Mechanize::Page
+      def back : Page
         @history.pop
       end
 
@@ -115,7 +116,7 @@ class Mechanize
       end
 
       # Sets a Referer header.
-      def set_request_referer(referer : Mechanize::Page?)
+      def set_request_referer(referer : Page?)
         return unless referer
 
         request_headers["Referer"] = referer.uri.to_s
diff --git a/src/mechanize/page.cr b/src/mechanize/page.cr
index ff952be..2d4336b 100644
--- a/src/mechanize/page.cr
+++ b/src/mechanize/page.cr
@@ -2,12 +2,12 @@ require "./file"
 require "./utils/element_matcher"
 require "./page/link"
 
-# This class represents the result of http response.
-# If you send a request, it returns the instance of `Mechanize::Page`.
-# You can get status code, title, and page body, and search html node using css selector from page instance.
 class Mechanize
+  # This class represents the result of http response.
+  # If you send a request, it returns the instance of `Mechanize::Page`.
+  # You can get status code, title, and page body, and search html node using css selector from page instance.
   class Page < Mechanize::File
-    include Mechanize::ElementMatcher
+    include ElementMatcher
 
     # look at lexbor document.(https://github.com/kostya/lexbor#readme)
     delegate :css, to: parser
@@ -42,7 +42,7 @@ class Mechanize
     # ```
     # page.forms # => Array(Mechanize::Form)
     # ```
-    def forms : Array(Mechanize::Form)
+    def forms : Array(Form)
       forms = css("form").map do |html_form|
         form = Form.new(html_form, self)
         form.action ||= @uri.to_s
@@ -54,7 +54,7 @@ class Mechanize
     # ```
     # page.links # => Array(Mechanize::PageContent::Link)
     # ```
-    def links : Array(Mechanize::PageContent::Link)
+    def links : Array(PageContent::Link)
       links = %w{a area}.map do |tag|
         css(tag).map do |node|
           PageContent::Link.new(node, @mech, self)
diff --git a/src/mechanize/page/link.cr b/src/mechanize/page/link.cr
index 2267f64..8bc9185 100644
--- a/src/mechanize/page/link.cr
+++ b/src/mechanize/page/link.cr
@@ -1,22 +1,24 @@
 # This class represents link element like <a> and <area>.
 # The instance of this class is clickable.
-class Mechanize::PageContent::Link
-  getter node : Lexbor::Node
-  getter page : Mechanize::Page
-  getter mech : Mechanize
-  getter href : String
-  getter text : String
+class Mechanize
+  class PageContent::Link
+    getter node : Lexbor::Node
+    getter page : Page
+    getter mech : Mechanize
+    getter href : String
+    getter text : String
 
-  def initialize(node, mech, page)
-    @node = node
-    @page = page
-    @mech = mech
-    @href = node.fetch("href", "")
-    @text = node.inner_text
-  end
+    def initialize(node, mech, page)
+      @node = node
+      @page = page
+      @mech = mech
+      @href = node.fetch("href", "")
+      @text = node.inner_text
+    end
 
-  # click on this link
-  def click
-    @mech.click self
+    # click on this link
+    def click
+      @mech.click self
+    end
   end
 end
diff --git a/src/mechanize/utils/element_matcher.cr b/src/mechanize/utils/element_matcher.cr
index a653125..9983d8a 100644
--- a/src/mechanize/utils/element_matcher.cr
+++ b/src/mechanize/utils/element_matcher.cr
@@ -65,7 +65,7 @@ class Mechanize
       def {{singular.id}}_with(criteria)
         f = {{plural.id}}_with(criteria)
         # TODO: Write correct error message.
-        raise Mechanize::ElementNotFoundError.new(:{{singular.id}}, "") if f.empty?
+        raise ElementNotFoundError.new(:{{singular.id}}, "") if f.empty?
         f.first
       end
     end