add checkbox comment

src/mechanize/form/check_box.cr

@@ -1,4 +1,6 @@
+# This class represents <input type="checkbox">
 class Mechanize::FormContent::CheckBox < Mechanize::FormContent::RadioButton
+  # set checkbox checked
   def check
     @checked = true
   end

src/mechanize/form/field.cr

@@ -1,6 +1,5 @@
 # This class represents <input> elements in the form.
 class Mechanize::FormContent::Field
-
   # returns field's 'value' attribute
   property value : String?
   # returns field's 'name' attribute

src/mechanize/form/multi_select_list.cr

@@ -1,5 +1,6 @@
 require "./option"
 
+# This class represents <select multiple>
 class Mechanize::FormContent::MultiSelectList
   getter node : Lexbor::Node
   getter name : String
@@ -18,32 +19,37 @@ class Mechanize::FormContent::MultiSelectList
     }
   end
 
+  # set all options unchecked
   def select_none
     @values = Array(String).new
     options.each &.unselect
   end
 
+  # set all options checked
   def select_all
     @values = Array(String).new
     options.each &.select
   end
 
+  # returns all checked options
   def selected_options
     options.select &.selected?
   end
 
+  # add new values to options
   def values=(new_values)
     select_none
     new_values.each do |value|
       option = options.find { |o| o.value == value }
       if option.nil?
-        @value.push(value)
+        @values.push(value)
       else
         option.select
       end
     end
   end
 
+  # return all option's values.
   def values
     @values + selected_options.map &.value
   end

src/mechanize/form/option.cr

@@ -30,6 +30,7 @@ class Mechanize::FormContent::Option
     @selected = !@selected
   end
 
+  # returns option checked or not
   def selected?
     @selected
   end

src/mechanize/form/radio_button.cr

@@ -1,3 +1,4 @@
+# This class represents <input type="radio">
 class Mechanize::FormContent::RadioButton < Mechanize::FormContent::Field
   property :checked, :form
 
@@ -7,19 +8,23 @@ class Mechanize::FormContent::RadioButton < Mechanize::FormContent::Field
     super(node)
   end
 
+  # set radiobutton checked
   def check
     uncheck_peers
     @checked = true
   end
 
+  # set radiobutton checked
   def uncheck
     @checked = false
   end
 
+  # change radiobutton state checked or unchecked
   def click
     checked ? uncheck : check
   end
 
+  # returns radiobutton checked or not
   def checked?
     checked
   end

src/mechanize/form/select_list.cr

@@ -1,5 +1,6 @@
 require "./multi_select_list"
 
+# This class represents <select> which is not multiple
 class Mechanize::FormContent::SelectList < Mechanize::FormContent::MultiSelectList
   def initialize(node)
     super node