diff --git a/.rubocop.yml b/.rubocop.yml
index c3af215..2194f7e 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,10 +1,551 @@
-# Omakase Ruby styling for Rails
-inherit_gem: { rubocop-rails-omakase: rubocop.yml }
-
-# Overwrite or add rules to create your own house style
-#
-# # Use `[a, [b, c]]` not `[ a, [ b, c ] ]`
-# Layout/SpaceInsideArrayLiteralBrackets:
-#   Enabled: false
+# This is rubocop configuration file for Sun-Asterisk's coding style. Enabling and disabling is configured
+# in separate files. This file adds all other parameters apart from Enabled.
+
+# Add this to load Rails extension for rubocop
+require: rubocop-rails
+
+# Put the following files into the same directory as this file.
+inherit_from:
+  - .rubocop_enabled.yml
+  - .rubocop_disabled.yml
+
+# Common configuration.
+AllCops:
+  # Include gemspec and Rakefile
+  SuggestExtensions: false
+  Include:
+    - 'app/**/*'
+    - 'lib/**/*'
+    - '**/*.gemspec'
+    - 'Gemfile'
+  Exclude:
+    - 'vendor/**/*'
+    - 'config/unicorn.rb'
+    - 'bin/*'
+    - 'db/**/*'
+    - 'spec/**/*'
+    - 'script/rails'
+    - 'config/**/*'
+    - 'app/views/**/*'
+    - 'app/assets/**/*'
+    - 'app/javascript/**/*'
+    - '.idea/**/*'
+    - '**/.DS_Store'
+    - '**/.keep'
+
+# Indent private/protected/public as deep as method definitions
+Layout/AccessModifierIndentation:
+  EnforcedStyle: indent
+  SupportedStyles:
+    - outdent
+    - indent
+
+# Align the elements of a hash literal if they span more than one line.
+Layout/HashAlignment:
+  # Alignment of entries using hash rocket as separator. Valid values are:
+  #
+  # key - left alignment of keys
+  #   'a' => 2
+  #   'bb' => 3
+  # separator - alignment of hash rockets, keys are right aligned
+  #    'a' => 2
+  #   'bb' => 3
+  # table - left alignment of keys, hash rockets, and values
+  #   'a'  => 2
+  #   'bb' => 3
+  EnforcedHashRocketStyle: key
+  # Alignment of entries using colon as separator. Valid values are:
+  #
+  # key - left alignment of keys
+  #   a: 0
+  #   bb: 1
+  # separator - alignment of colons, keys are right aligned
+  #    a: 0
+  #   bb: 1
+  # table - left alignment of keys and values
+  #   a:  0
+  #   bb: 1
+  EnforcedColonStyle: key
+  # Select whether hashes that are the last argument in a method call should be
+  # inspected? Valid values are:
+  #
+  # always_inspect - Inspect both implicit and explicit hashes.
+  #   Registers an offense for:
+  #     function(a: 1,
+  #       b: 2)
+  #   Registers an offense for:
+  #     function({a: 1,
+  #       b: 2})
+  # always_ignore - Ignore both implicit and explicit hashes.
+  #   Accepts:
+  #     function(a: 1,
+  #       b: 2)
+  #   Accepts:
+  #     function({a: 1,
+  #       b: 2})
+  # ignore_implicit - Ignore only implicit hashes.
+  #   Accepts:
+  #     function(a: 1,
+  #       b: 2)
+  #   Registers an offense for:
+  #     function({a: 1,
+  #       b: 2})
+  # ignore_explicit - Ignore only explicit hashes.
+  #   Accepts:
+  #     function({a: 1,
+  #       b: 2})
+  #   Registers an offense for:
+  #     function(a: 1,
+  #       b: 2)
+  EnforcedLastArgumentHashStyle: ignore_implicit
+  SupportedLastArgumentHashStyles:
+    - always_inspect
+    - always_ignore
+    - ignore_implicit
+    - ignore_explicit
+
+Layout/ParameterAlignment:
+  # Alignment of parameters in multi-line method calls.
+  #
+  # The `with_first_parameter` style aligns the following lines along the same column
+  # as the first parameter.
+  #
+  #     method_call(a,
+  #                 b)
+  #
+  # The `with_fixed_indentation` style aligns the following lines with one
+  # level of indentation relative to the start of the line with the method call.
+  #
+  #     method_call(a,
+  #       b)
+  EnforcedStyle: with_fixed_indentation
+  SupportedStyles:
+    - with_first_parameter
+    - with_fixed_indentation
+
+Metrics/BlockNesting:
+  Max: 3
+
+Metrics/AbcSize:
+  # The ABC size is a calculated magnitude, so this number can be a Fixnum or
+  # a Float.
+  Max: 20
+
+# Indentation of `when`.
+Layout/CaseIndentation:
+  EnforcedStyle: case
+  SupportedStyles:
+    - case
+    - end
+  IndentOneStep: false
+
+Style/ClassAndModuleChildren:
+  # Checks the style of children definitions at classes and modules.
+  #
+  # Basically there are two different styles:
+  #
+  # `nested` - have each child on a separate line
+  #   class Foo
+  #     class Bar
+  #     end
+  #   end
+  #
+  # `compact` - combine definitions as much as possible
+  #   class Foo::Bar
+  #   end
+  #
+  # The compact style is only forced, for classes / modules with one child.
+  EnforcedStyle: nested
+  SupportedStyles:
+    - nested
+    - compact
+
+Style/ClassCheck:
+  EnforcedStyle: is_a?
+  SupportedStyles:
+    - is_a?
+    - kind_of?
+
+Metrics/ClassLength:
+  CountComments: false  # count full line comments?
+  Max: 100
+
+# Align with the style guide.
+Style/CollectionMethods:
+  # Mapping from undesired method to desired_method
+  # e.g. to use `detect` over `find`:
+  #
+  # CollectionMethods:
+  #   PreferredMethods:
+  #     find: detect
+  PreferredMethods:
+    collect: 'map'
+    collect!: 'map!'
+    inject: 'reduce'
+    detect: 'find'
+    find_all: 'select'
+
+# Checks formatting of special comments
+Style/CommentAnnotation:
+  Keywords:
+    - TODO
+    - FIXME
+    - OPTIMIZE
+    - HACK
+    - REVIEW
+
+# Avoid complex methods.
+Metrics/CyclomaticComplexity:
+  Max: 6
+
+# Multi-line method chaining should be done with leading dots.
+Layout/DotPosition:
+  EnforcedStyle: leading
+  SupportedStyles:
+    - leading
+    - trailing
+
+# Use empty lines between defs.
+Layout/EmptyLineBetweenDefs:
+  # If true, this parameter means that single line method definitions don't
+  # need an empty line between them.
+  AllowAdjacentOneLineDefs: false
+
+Layout/EmptyLinesAroundBlockBody:
+  EnforcedStyle: no_empty_lines
+  SupportedStyles:
+    - no_empty_lines
+
+Layout/EmptyLinesAroundClassBody:
+  EnforcedStyle: no_empty_lines
+  SupportedStyles:
+    - no_empty_lines
+
+Layout/EmptyLinesAroundModuleBody:
+  EnforcedStyle: no_empty_lines
+  SupportedStyles:
+    - no_empty_lines
+
+Naming/FileName:
+  Exclude:
+    - '**/Rakefile'
+    - '**/Gemfile'
+    - '**/Capfile'
+
+# Checks use of for or each in multiline loops.
+Style/For:
+  EnforcedStyle: each
+  SupportedStyles:
+    - for
+    - each
+
+# Enforce the method used for string formatting.
+Style/FormatString:
+  EnforcedStyle: format
+  SupportedStyles:
+    - format
+    - sprintf
+    - percent
+
+# Built-in global variables are allowed by default.
+Style/GlobalVars:
+  AllowedVariables: []
+
+# `MinBodyLength` defines the number of lines of the a body of an if / unless
+# needs to have to trigger this cop
+Style/GuardClause:
+  MinBodyLength: 1
+
+Style/HashSyntax:
+  EnforcedStyle: ruby19
+  SupportedStyles:
+    - ruby19
+    - hash_rockets
+
+# Checks the indentation of the first key in a hash literal.
+Layout/FirstHashElementIndentation:
+  # The value `special_inside_parentheses` means that hash literals with braces
+  # that have their opening brace on the same line as a surrounding opening
+  # round parenthesis, shall have their first key indented relative to the
+  # first position inside the parenthesis.
+  # The value `consistent` means that the indentation of the first key shall
+  # always be relative to the first position of the line where the opening
+  # brace is.
+  EnforcedStyle: special_inside_parentheses
+  SupportedStyles:
+    - special_inside_parentheses
+    - consistent
+
+Style/LambdaCall:
+  EnforcedStyle: call
+  SupportedStyles:
+    - call
+    - braces
+
+Metrics/LineLength:
+  Max: 80
+  AllowURI: true
+  Exclude:
+    - config/routes.rb
+
+
+Style/Next:
+  # With `always` all conditions at the end of an iteration needs to be
+  # replace by next - with `skip_modifier_ifs` the modifier if like this one
+  # are ignored: [1, 2].each { |a| return 'yes' if a == 1 }
+  EnforcedStyle: skip_modifier_ifs
+  SupportedStyles:
+    - skip_modifier_ifs
+    - always
+
+Style/NonNilCheck:
+  # With `IncludeSemanticChanges` set to `true`, this cop reports offenses for
+  # `!x.nil?` and autocorrects that and `x != nil` to solely `x`, which is
+  # **usually** OK, but might change behavior.
+  #
+  # With `IncludeSemanticChanges` set to `false`, this cop does not report
+  # offenses for `!x.nil?` and does no changes that might change behavior.
+  IncludeSemanticChanges: false
+
 Style/MethodDefParentheses:
-  Enabled: false
+  EnforcedStyle: require_no_parentheses
+  SupportedStyles:
+    - require_parentheses
+    - require_no_parentheses
+
+Metrics/MethodLength:
+  CountComments: false  # count full line comments?
+  Max: 10
+
+Naming/MethodName:
+  EnforcedStyle: snake_case
+  SupportedStyles:
+    - snake_case
+    - camelCase
+
+Style/NumericLiterals:
+  MinDigits: 5
+
+Metrics/ParameterLists:
+  Max: 5
+  CountKeywordArgs: true
+
+# Allow safe assignment in conditions.
+Style/ParenthesesAroundCondition:
+  AllowSafeAssignment: true
+
+Style/PercentLiteralDelimiters:
+  PreferredDelimiters:
+    '%':  ()
+    '%i': ()
+    '%q': ()
+    '%Q': ()
+    '%r': '{}'
+    '%s': ()
+    '%w': ()
+    '%W': ()
+    '%x': ()
+
+Style/RaiseArgs:
+  EnforcedStyle: exploded
+  SupportedStyles:
+    - compact # raise Exception.new(msg)
+    - exploded # raise Exception, msg
+
+
+Style/RedundantReturn:
+  # When true allows code like `return x, y`.
+  AllowMultipleReturnValues: false
+
+#Style/RegexpLiteral:
+#  # The maximum number of (escaped) slashes that a slash-delimited regexp is
+#  # allowed to have. If there are more slashes, a %r regexp shall be used.
+#  MaxSlashes: 0
+
+Style/Semicolon:
+  # Allow ; to separate several expressions on the same line.
+  AllowAsExpressionSeparator: false
+
+Style/SignalException:
+  EnforcedStyle: only_raise
+  SupportedStyles:
+    - only_raise
+    - only_fail
+    - semantic
+
+
+Style/SingleLineBlockParams:
+  Methods:
+    - reduce:
+        - a
+        - e
+    - inject:
+        - a
+        - e
+
+Style/SingleLineMethods:
+  AllowIfMethodIsEmpty: true
+
+Style/StringLiterals:
+  EnforcedStyle: double_quotes
+  SupportedStyles:
+    - single_quotes
+    - double_quotes
+
+Layout/SpaceAroundEqualsInParameterDefault:
+  EnforcedStyle: space
+  SupportedStyles:
+    - space
+    - no_space
+
+Layout/SpaceBeforeBlockBraces:
+  EnforcedStyle: no_space
+  SupportedStyles:
+    - space
+    - no_space
+
+Layout/SpaceInsideBlockBraces:
+  EnforcedStyle: no_space
+  SupportedStyles:
+    - space
+    - no_space
+  # Valid values are: space, no_space
+  EnforcedStyleForEmptyBraces: no_space
+  # Space between { and |. Overrides EnforcedStyle if there is a conflict.
+  SpaceBeforeBlockParameters: false
+
+Layout/SpaceInsideHashLiteralBraces:
+  EnforcedStyle: no_space
+  EnforcedStyleForEmptyBraces: no_space
+  SupportedStyles:
+    - space
+    - no_space
+
+Layout/TrailingEmptyLines:
+  EnforcedStyle: final_newline
+  SupportedStyles:
+    - final_newline
+    - final_blank_line
+
+Style/TrailingCommaInArguments:
+  # If `comma`, the cop requires a comma after the last argument, but only for
+  # parenthesized method calls where each argument is on its own line.
+  # If `consistent_comma`, the cop requires a comma after the last argument,
+  # for all parenthesized method calls with arguments.
+  EnforcedStyleForMultiline: no_comma
+  SupportedStylesForMultiline:
+    - comma
+    - consistent_comma
+    - no_comma
+
+Style/TrailingCommaInArrayLiteral:
+  # If `comma`, the cop requires a comma after the last item in an array,
+  # but only when each item is on its own line.
+  # If `consistent_comma`, the cop requires a comma after the last item of all
+  # non-empty array literals.
+  EnforcedStyleForMultiline: no_comma
+  SupportedStylesForMultiline:
+    - comma
+    - consistent_comma
+    - no_comma
+
+Style/TrailingCommaInHashLiteral:
+  # If `comma`, the cop requires a comma after the last item in a hash,
+  # but only when each item is on its own line.
+  # If `consistent_comma`, the cop requires a comma after the last item of all
+  # non-empty hash literals.
+  EnforcedStyleForMultiline: no_comma
+  SupportedStylesForMultiline:
+    - comma
+    - consistent_comma
+    - no_comma
+
+# TrivialAccessors doesn't require exact name matches and doesn't allow
+# predicated methods by default.
+Style/TrivialAccessors:
+  ExactNameMatch: false
+  AllowPredicates: false
+  # Allows trivial writers that don't end in an equal sign. e.g.
+  #
+  # def on_exception(action)
+  #   @on_exception=action
+  # end
+  # on_exception :restart
+  #
+  # Commonly used in DSLs
+  AllowDSLWriters: false
+  AllowedMethods:
+    - to_ary
+    - to_a
+    - to_c
+    - to_enum
+    - to_h
+    - to_hash
+    - to_i
+    - to_int
+    - to_io
+    - to_open
+    - to_path
+    - to_proc
+    - to_r
+    - to_regexp
+    - to_str
+    - to_s
+    - to_sym
+
+Naming/VariableName:
+  EnforcedStyle: snake_case
+  SupportedStyles:
+    - snake_case
+    - camelCase
+
+Style/WordArray:
+  MinSize: 0
+
+##################### Lint ##################################
+
+# Allow safe assignment in conditions.
+Lint/AssignmentInCondition:
+  AllowSafeAssignment: true
+
+# Align ends correctly.
+Layout/EndAlignment:
+  # The value `keyword` means that `end` should be aligned with the matching
+  # keyword (if, while, etc.).
+  # The value `variable` means that in assignments, `end` should be aligned
+  # with the start of the variable on the left hand side of `=`. In all other
+  # situations, `end` should still be aligned with the keyword.
+  EnforcedStyleAlignWith: keyword
+
+Layout/DefEndAlignment:
+  # The value `def` means that `end` should be aligned with the def keyword.
+  # The value `start_of_line` means that `end` should be aligned with method
+  # calls like `private`, `public`, etc, if present in front of the `def`
+  # keyword on the same line.
+  EnforcedStyleAlignWith: start_of_line
+
+##################### Rails ##################################
+
+Rails/ActionFilter:
+  EnforcedStyle: action
+  SupportedStyles:
+    - action
+    - filter
+  Include:
+    - app/controllers/**/*.rb
+
+Rails/HasAndBelongsToMany:
+  Include:
+    - app/models/**/*.rb
+
+Rails/ReadWriteAttribute:
+  Include:
+    - app/models/**/*.rb
+
+Rails/ScopeArgs:
+  Include:
+    - app/models/**/*.rb
+
+Rails/Validation:
+  Include:
+    - app/models/**/*.rb
diff --git a/.rubocop_disabled.yml b/.rubocop_disabled.yml
new file mode 100644
index 0000000..52cf287
--- /dev/null
+++ b/.rubocop_disabled.yml
@@ -0,0 +1,86 @@
+# These are all the cops that are disabled in the default configuration.
+
+Style/FrozenStringLiteralComment:
+  Description: >-
+                 Add the frozen_string_literal comment to the top of files
+                 to help transition from Ruby 2.3.0 to Ruby 3.0.
+  Enabled: false
+
+Style/InlineComment:
+  Description: "Avoid inline comments."
+  Enabled: false
+
+Style/MethodCalledOnDoEndBlock:
+  Description: "Avoid chaining a method call on a do...end block."
+  Enabled: false
+
+Style/SymbolArray:
+  Description: "Use %i or %I for arrays of symbols."
+  Enabled: false
+
+Style/Documentation:
+  Description: "Document classes and non-namespace modules."
+  Enabled: false
+
+Layout/EmptyLinesAroundAccessModifier:
+  Description: "Keep blank lines around access modifiers."
+  Enabled: false
+
+Style/EmptyLiteral:
+  Description: "Prefer literals to Array.new/Hash.new/String.new."
+  Enabled: false
+
+Style/ClassAndModuleChildren:
+  Description: "Checks style of children classes and modules."
+  Enabled: false
+
+Metrics/ClassLength:
+  Description: "Avoid classes longer than 100 lines of code."
+  Enabled: false
+
+Metrics/MethodLength:
+  Description: "Avoid methods longer than 10 lines of code."
+  Enabled: false
+
+Metrics/ParameterLists:
+  Description: "Avoid parameter lists longer than three or four parameters."
+  Enabled: false
+
+Metrics/CyclomaticComplexity:
+  Description: "Avoid complex methods."
+  Enabled: false
+
+Layout/ArrayAlignment:
+  Description: >-
+                 Align the elements of an array literal if they span more than
+                 one line.
+  Enabled: false
+
+Style/RedundantPercentQ:
+  Description: "Checks for %q/%Q when single quotes or double quotes would do."
+  Enabled: false
+
+Naming/AccessorMethodName:
+  Description: Check the naming of accessor methods for get_/set_.
+  Enabled: false
+
+#################### Lint ################################
+### Warnings
+Lint/AssignmentInCondition:
+  Description: "Don't use assignment in conditions."
+  Enabled: false
+
+Rails/HelperInstanceVariable:
+  Description: "Do not use instance variables in helpers"
+  Enabled: false
+
+Rails/InverseOf:
+  Description: "Prevent fetching loaded data again through a relationship."
+  Enabled: false
+
+Rails/ReflectionClassName:
+  Description: "Use a string for `class_name` option value in the definition of a reflection."
+  Enabled: false
+
+Rails/SkipsModelValidations:
+  Enabled: false
diff --git a/.rubocop_enabled.yml b/.rubocop_enabled.yml
new file mode 100644
index 0000000..5da7068
--- /dev/null
+++ b/.rubocop_enabled.yml
@@ -0,0 +1,745 @@
+# These are all the cops that are enabled in the default configuration.
+
+Layout/AccessModifierIndentation:
+  Description: Check indentation of private/protected visibility modifiers.
+  Enabled: true
+
+Style/Alias:
+  Description: "Use alias_method instead of alias."
+  Enabled: true
+
+Layout/HashAlignment:
+  Description: >-
+                 Align the elements of a hash literal if they span more than
+                 one line.
+  Enabled: true
+
+Layout/Layout/ParameterAlignment:
+  Description: >-
+                 Align the parameters of a method call if they span more
+                 than one line.
+  Enabled: true
+
+Style/AndOr:
+  Description: "Use &&/|| instead of and/or."
+  Enabled: true
+
+Style/ArrayJoin:
+  Description: "Use Array#join instead of Array#*."
+  Enabled: true
+
+Style/AsciiComments:
+  Description: "Use only ascii symbols in comments."
+  Enabled: true
+
+Naming/AsciiIdentifiers:
+  Description: "Use only ascii symbols in identifiers."
+  Enabled: true
+
+Style/Attr:
+  Description: "Checks for uses of Module#attr."
+  Enabled: true
+
+Style/BeginBlock:
+  Description: "Avoid the use of BEGIN blocks."
+  Enabled: true
+
+Style/BlockComments:
+  Description: "Do not use block comments."
+  Enabled: true
+
+Metrics/BlockNesting:
+  Description: "Avoid excessive block nesting"
+  Enabled: true
+
+Style/BlockDelimiters:
+  Description: >-
+                Avoid using {...} for multi-line blocks (multiline chaining is
+                always ugly).
+                Prefer {...} over do...end for single-line blocks.
+  Enabled: true
+
+Style/CaseEquality:
+  Description: "Avoid explicit use of the case equality operator(===)."
+  Enabled: true
+
+Layout/CaseIndentation:
+  Description: "Indentation of when in a case/when/[else/]end."
+  Enabled: true
+
+Style/CharacterLiteral:
+  Description: "Checks for uses of character literals."
+  Enabled: true
+
+Naming/ClassAndModuleCamelCase:
+  Description: "Use CamelCase for classes and modules."
+  Enabled: true
+
+Style/ClassAndModuleChildren:
+  Description: "Checks style of children classes and modules."
+  Enabled: true
+
+Style/ClassCheck:
+  Description: "Enforces consistent use of `Object#is_a?` or `Object#kind_of?`."
+  Enabled: true
+
+Style/ClassMethods:
+  Description: "Use self when defining module/class methods."
+  Enabled: true
+
+Style/ClassVars:
+  Description: "Avoid the use of class variables."
+  Enabled: true
+
+Style/CollectionMethods:
+  Description: "Preferred collection methods."
+  Enabled: true
+
+Style/ColonMethodCall:
+  Description: "Do not use :: for method call."
+  Enabled: true
+
+Style/CommentAnnotation:
+  Description: >-
+                 Checks formatting of special comments
+                 (TODO, FIXME, OPTIMIZE, HACK, REVIEW).
+  Enabled: true
+
+Layout/CommentIndentation:
+  Description: "Indentation of comments."
+  Enabled: true
+
+Naming/ConstantName:
+  Description: "Constants should use SCREAMING_SNAKE_CASE."
+  Enabled: true
+
+Style/DefWithParentheses:
+  Description: "Use def with parentheses when there are arguments."
+  Enabled: true
+
+Style/PreferredHashMethods:
+  Description: "Checks for use of deprecated Hash methods."
+  Enabled: true
+
+Style/Documentation:
+  Description: "Document classes and non-namespace modules."
+  Enabled: true
+
+Layout/DotPosition:
+  Description: "Checks the position of the dot in multi-line method calls."
+  Enabled: true
+
+Style/DoubleNegation:
+  Description: "Checks for uses of double negation (!!)."
+  Enabled: true
+
+Style/EachWithObject:
+  Description: "Prefer `each_with_object` over `inject` or `reduce`."
+  Enabled: true
+
+Layout/EmptyLineBetweenDefs:
+  Description: "Use empty lines between defs."
+  Enabled: true
+
+Layout/EmptyLines:
+  Description: "Don't use several empty lines in a row."
+  Enabled: true
+
+Layout/EmptyLinesAroundAccessModifier:
+  Description: "Keep blank lines around access modifiers."
+  Enabled: true
+
+Layout/EmptyLinesAroundBlockBody:
+  Description: "Keeps track of empty lines around expression bodies."
+  Enabled: true
+
+Layout/EmptyLinesAroundClassBody:
+  Description: "Keeps track of empty lines around expression classes."
+  Enabled: true
+
+Layout/EmptyLinesAroundModuleBody:
+  Description: "Keeps track of empty lines around expression modules."
+  Enabled: true
+
+Style/EmptyLiteral:
+  Description: "Prefer literals to Array.new/Hash.new/String.new."
+  Enabled: true
+
+Style/Encoding:
+  Description: "Use UTF-8 as the source file encoding."
+  Enabled: true
+
+Style/EndBlock:
+  Description: "Avoid the use of END blocks."
+  Enabled: true
+
+Layout/EndOfLine:
+  Description: "Use Unix-style line endings."
+  Enabled: true
+
+Style/EvenOdd:
+  Description: "Favor the use of Fixnum#even? && Fixnum#odd?"
+  Enabled: true
+
+Naming/FileName:
+  Description: "Use snake_case for source file names."
+  Enabled: true
+
+Lint/FlipFlop:
+  Description: "Checks for flip flops"
+  Enabled: true
+
+Style/For:
+  Description: "Checks use of for or each in multiline loops."
+  Enabled: true
+
+Style/FormatString:
+  Description: "Enforce the use of Kernel#sprintf, Kernel#format or String#%."
+  Enabled: true
+
+Style/GlobalVars:
+  Description: "Do not introduce global variables."
+  Enabled: true
+
+Style/GuardClause:
+  Description: "Check for conditionals that can be replaced with guard clauses"
+  Enabled: true
+
+Style/HashSyntax:
+  Description: >-
+                 Prefer Ruby 1.9 hash syntax { a: 1, b: 2 } over 1.8 syntax
+                 { :a => 1, :b => 2 }.
+  Enabled: true
+
+Style/IfUnlessModifier:
+  Description: >-
+                 Favor modifier if/unless usage when you have a
+                 single-line body.
+  Enabled: true
+
+Style/IfWithSemicolon:
+  Description: "Never use if x; .... Use the ternary operator instead."
+  Enabled: true
+
+Layout/IndentationConsistency:
+  Description: "Keep indentation straight."
+  Enabled: true
+
+Layout/IndentationWidth:
+  Description: "Use 2 spaces for indentation."
+  Enabled: true
+
+Layout/FirstArrayElementIndentation:
+  Description: >-
+                 Checks the indentation of the first element in an array
+                 literal.
+  Enabled: true
+
+Layout/FirstHashElementIndentation:
+  Description: "Checks the indentation of the first key in a hash literal."
+  Enabled: true
+
+Style/Lambda:
+  Description: "Use the new lambda literal syntax for single-line blocks."
+  Enabled: true
+
+Style/LambdaCall:
+  Description: "Use lambda.call(...) instead of lambda.(...)."
+  Enabled: true
+
+Layout/LeadingCommentSpace:
+  Description: "Comments should start with a space."
+  Enabled: true
+
+Style/LineEndConcatenation:
+  Description: >-
+                 Use \ instead of + or << to concatenate two string literals at
+                 line end.
+  Enabled: true
+
+Metrics/LineLength:
+  Description: "Limit lines to 80 characters."
+  Enabled: true
+
+Style/MethodCallWithoutArgsParentheses:
+  Description: "Do not use parentheses for method calls with no arguments."
+  Enabled: true
+
+Style/MethodDefParentheses:
+  Description: >-
+                 Checks if the method definitions have or don"t have
+                 parentheses.
+  Enabled: true
+
+Naming/MethodName:
+  Description: "Use the configured style when naming methods."
+  Enabled: true
+
+Style/ModuleFunction:
+  Description: "Checks for usage of `extend self` in modules."
+  Enabled: true
+
+Style/MultilineBlockChain:
+  Description: "Avoid multi-line chains of blocks."
+  Enabled: true
+
+Style/MultilineIfThen:
+  Description: "Never use then for multi-line if/unless."
+  Enabled: true
+
+Style/MultilineTernaryOperator:
+  Description: >-
+                 Avoid multi-line ?: (the ternary operator);
+                 use if/unless instead.
+  Enabled: true
+
+Style/NegatedIf:
+  Description: >-
+                 Favor unless over if for negative conditions
+                 (or control flow or).
+  Enabled: true
+
+Style/NegatedWhile:
+  Description: "Favor until over while for negative conditions."
+  Enabled: true
+
+Style/NestedTernaryOperator:
+  Description: "Use one expression per branch in a ternary operator."
+  Enabled: true
+
+Style/Next:
+  Description: "Use `next` to skip iteration instead of a condition at the end."
+  Enabled: true
+
+Style/NilComparison:
+  Description: "Prefer x.nil? to x == nil."
+  Enabled: true
+
+Style/NonNilCheck:
+  Description: "Checks for redundant nil checks."
+  Enabled: true
+
+Style/Not:
+  Description: "Use ! instead of not."
+  Enabled: true
+
+Style/NumericLiterals:
+  Description: >-
+                 Add underscores to large numeric literals to improve their
+                 readability.
+  Enabled: true
+
+Style/OneLineConditional:
+  Description: >-
+                 Favor the ternary operator(?:) over
+                 if/then/else/end constructs.
+  Enabled: true
+
+Naming/BinaryOperatorParameterName:
+  Description: "When defining binary operators, name the argument other."
+  Enabled: true
+
+Style/ParenthesesAroundCondition:
+  Description: >-
+                 Don't use parentheses around the condition of an
+                 if/unless/while.
+  Enabled: true
+
+Style/PercentLiteralDelimiters:
+  Description: "Use `%`-literal delimiters consistently"
+  Enabled: true
+
+Style/PerlBackrefs:
+  Description: "Avoid Perl-style regex back references."
+  Enabled: true
+
+Naming/PredicateName:
+  Description: "Check the names of predicate methods."
+  Enabled: true
+
+Style/Proc:
+  Description: "Use proc instead of Proc.new."
+  Enabled: true
+
+Style/RaiseArgs:
+  Description: "Checks the arguments passed to raise/fail."
+  Enabled: true
+
+Style/RedundantBegin:
+  Description: "Don't use begin blocks when they are not needed."
+  Enabled: true
+
+Style/RedundantException:
+  Description: "Checks for an obsolete RuntimeException argument in raise/fail."
+  Enabled: true
+
+Style/RedundantReturn:
+  Description: "Don't use return where it's not required."
+  Enabled: true
+
+Style/RedundantSelf:
+  Description: "Don't use self where it's not needed."
+  Enabled: true
+
+Style/RegexpLiteral:
+  Description: >-
+                 Use %r for regular expressions matching more than
+                 `MaxSlashes` '/' characters.
+                 Use %r only for regular expressions matching more than
+                 `MaxSlashes` '/' character.
+  Enabled: true
+
+Style/RescueModifier:
+  Description: "Avoid using rescue in its modifier form."
+  Enabled: true
+
+Style/SelfAssignment:
+  Description: "Checks for places where self-assignment shorthand should have been used."
+  Enabled: true
+
+Style/Semicolon:
+  Description: "Don't use semicolons to terminate expressions."
+  Enabled: true
+
+Style/SignalException:
+  Description: "Checks for proper usage of fail and raise."
+  Enabled: true
+
+Style/SingleLineBlockParams:
+  Description: "Enforces the names of some block params."
+  Enabled: true
+
+Style/SingleLineMethods:
+  Description: "Avoid single-line methods."
+  Enabled: true
+
+Layout/SpaceBeforeFirstArg:
+  Description: >-
+                 Checks that exactly one space is used between a method name
+                 and the first argument for method calls without parentheses.
+  Enabled: true
+
+Layout/SpaceAfterColon:
+  Description: "Use spaces after colons."
+  Enabled: true
+
+Layout/SpaceAfterComma:
+  Description: "Use spaces after commas."
+  Enabled: true
+
+Layout/SpaceAroundKeyword:
+  Description: "Use spaces after if/elsif/unless/while/until/case/when."
+  Enabled: true
+
+Layout/SpaceAfterMethodName:
+  Description: >-
+                 Never put a space between a method name and the opening
+                 parenthesis in a method definition.
+  Enabled: true
+
+Layout/SpaceAfterNot:
+  Description: Tracks redundant space after the ! operator.
+  Enabled: true
+
+Layout/SpaceAfterSemicolon:
+  Description: "Use spaces after semicolons."
+  Enabled: true
+
+Layout/SpaceBeforeBlockBraces:
+  Description: >-
+                 Checks that the left block brace has or doesn't have space
+                 before it.
+  Enabled: true
+
+Layout/SpaceBeforeComma:
+  Description: "No spaces before commas."
+  Enabled: true
+
+Layout/SpaceBeforeComment:
+  Description: >-
+                 Checks for missing space between code and a comment on the
+                 same line.
+  Enabled: true
+
+Layout/SpaceBeforeSemicolon:
+  Description: "No spaces before semicolons."
+  Enabled: true
+
+Layout/SpaceInsideBlockBraces:
+  Description: >-
+                 Checks that block braces have or don't have surrounding space.
+                 For blocks taking parameters, checks that the left brace has
+                 or doesn"t have trailing space.
+  Enabled: true
+
+Layout/SpaceAroundEqualsInParameterDefault:
+  Description: >-
+                 Checks that the equals signs in parameter default assignments
+                 have or don't have surrounding space depending on
+                 configuration.
+  Enabled: true
+
+Layout/SpaceAroundOperators:
+  Description: "Use spaces around operators."
+  Enabled: true
+
+Layout/SpaceInsideHashLiteralBraces:
+  Description: "Use spaces inside hash literal braces - or don't."
+  Enabled: true
+
+Layout/SpaceInsideParens:
+  Description: "No spaces after ( or before )."
+  Enabled: true
+
+Style/SpecialGlobalVars:
+  Description: "Avoid Perl-style global variables."
+  Enabled: true
+
+Style/StringLiterals:
+  Description: "Checks if uses of quotes match the configured preference."
+  Enabled: true
+
+Layout/IndentationStyle:
+  Description: "No hard tabs."
+  Enabled: true
+
+Layout/TrailingEmptyLines:
+  Description: "Checks trailing blank lines and final newline."
+  Enabled: true
+
+Style/TrailingCommaInArguments:
+  Description: 'Checks for trailing comma in argument lists.'
+  StyleGuide: '#no-trailing-params-comma'
+  Enabled: true
+
+Style/TrailingCommaInArrayLiteral:
+  Description: 'Checks for trailing comma in array literals.'
+  StyleGuide: '#no-trailing-array-commas'
+  Enabled: true
+
+Style/TrailingCommaInHashLiteral:
+  Description: 'Checks for trailing comma in hash literals.'
+  Enabled: true
+
+Layout/TrailingWhitespace:
+  Description: "Avoid trailing whitespace."
+  Enabled: true
+
+Style/TrivialAccessors:
+  Description: "Prefer attr_* methods to trivial readers/writers."
+  Enabled: true
+
+Style/UnlessElse:
+  Description: >-
+                 Never use unless with else. Rewrite these with the positive
+                 case first.
+  Enabled: true
+
+Style/RedundantCapitalW:
+  Description: "Checks for %W when interpolation is not needed."
+  Enabled: true
+
+Style/CommandLiteral:
+  Description: "Checks for %x when `` would do."
+  Enabled: true
+
+Style/VariableInterpolation:
+  Description: >-
+                 Don't interpolate global, instance and class variables
+                 directly in strings.
+  Enabled: true
+
+Naming/VariableName:
+  Description: "Use the configured style when naming variables."
+  Enabled: true
+
+Style/WhenThen:
+  Description: "Use when x then ... for one-line cases."
+  Enabled: true
+
+Style/WhileUntilDo:
+  Description: "Checks for redundant do after while or until."
+  Enabled: true
+
+Style/WhileUntilModifier:
+  Description: >-
+                 Favor modifier while/until usage when you have a
+                 single-line body.
+  Enabled: true
+
+Style/WordArray:
+  Description: "Use %w or %W for arrays of words."
+  Enabled: true
+
+#################### Lint ################################
+### Warnings
+
+Lint/AmbiguousOperator:
+  Description: >-
+                 Checks for ambiguous operators in the first argument of a
+                 method invocation without parentheses.
+  Enabled: true
+
+Lint/AmbiguousRegexpLiteral:
+  Description: >-
+                 Checks for ambiguous regexp literals in the first argument of
+                 a method invocation without parenthesis.
+  Enabled: true
+
+Layout/BlockAlignment:
+  Description: "Align block ends correctly."
+  Enabled: true
+
+Layout/ConditionPosition:
+  Description: "Checks for condition placed in a confusing position relative to the keyword."
+  Enabled: true
+
+Lint/Debugger:
+  Description: "Check for debugger calls."
+  Enabled: true
+
+Layout/DefEndAlignment:
+  Description: "Align ends corresponding to defs correctly."
+  Enabled: true
+
+Lint/DeprecatedClassMethods:
+  Description: "Check for deprecated class method calls."
+  Enabled: true
+
+Lint/ElseLayout:
+  Description: "Check for odd code arrangement in an else block."
+  Enabled: true
+
+Lint/EmptyEnsure:
+  Description: "Checks for empty ensure block."
+  Enabled: true
+
+Lint/EmptyInterpolation:
+  Description: "Checks for empty string interpolation."
+  Enabled: true
+
+Layout/EndAlignment:
+  Description: "Align ends correctly."
+  Enabled: true
+
+Style/EndBlock:
+  Description: "END blocks should not be placed inside method definitions."
+  Enabled: true
+
+Lint/EnsureReturn:
+  Description: "Never use return in an ensure block."
+  Enabled: true
+
+Security/Eval:
+  Description: "The use of eval represents a serious security risk."
+  Enabled: true
+
+Lint/SuppressedException:
+  Description: "Don't suppress exception."
+  Enabled: true
+
+Lint/LiteralInInterpolation:
+  Description: "Checks for literals used in interpolation."
+  Enabled: true
+
+Lint/Loop:
+  Description: >-
+                 Use Kernel#loop with break rather than begin/end/until or
+                 begin/end/while for post-loop tests.
+  Enabled: true
+
+Lint/ParenthesesAsGroupedExpression:
+  Description: >-
+                 Checks for method calls with a space before the opening
+                 parenthesis.
+  Enabled: true
+
+Lint/RequireParentheses:
+  Description: >-
+                 Use parentheses in the method call to avoid confusion
+                 about precedence.
+  Enabled: true
+
+Lint/RescueException:
+  Description: "Avoid rescuing the Exception class."
+  Enabled: true
+
+Lint/ShadowingOuterLocalVariable:
+  Description: >-
+                 Do not use the same name as outer local variable
+                 for block arguments or block local variables.
+  Enabled: true
+
+Lint/RedundantStringCoercion:
+  Description: "Checks for Object#to_s usage in string interpolation."
+  Enabled: true
+
+Lint/UnderscorePrefixedVariableName:
+  Description: "Do not use prefix `_` for a variable that is used."
+  Enabled: true
+
+Lint/UnusedBlockArgument:
+  Description: "Checks for unused block arguments."
+  Enabled: true
+
+Lint/UnusedMethodArgument:
+  Description: "Checks for unused method arguments."
+  Enabled: true
+
+Lint/UnreachableCode:
+  Description: "Unreachable code."
+  Enabled: true
+
+Lint/UselessAccessModifier:
+  Description: "Checks for useless access modifiers."
+  Enabled: true
+
+Lint/UselessAssignment:
+  Description: "Checks for useless assignment to a local variable."
+  Enabled: true
+
+Lint/BinaryOperatorWithIdenticalOperands:
+  Description: "Checks for comparison of something with itself."
+  Enabled: true
+
+Lint/UselessElseWithoutRescue:
+  Description: "Checks for useless `else` in `begin..end` without `rescue`."
+  Enabled: true
+
+Lint/UselessSetterCall:
+  Description: "Checks for useless setter call to a local variable."
+  Enabled: true
+
+Lint/Void:
+  Description: "Possible use of operator/literal/variable in void context."
+  Enabled: true
+
+##################### Rails ##################################
+
+Rails/ActionFilter:
+  Description: "Enforces consistent use of action filter methods."
+  Enabled: true
+
+Rails/Delegate:
+  Description: "Prefer delegate method for delegations."
+  Enabled: true
+
+Rails/HasAndBelongsToMany:
+  Description: "Prefer has_many :through to has_and_belongs_to_many."
+  Enabled: true
+
+Rails/Output:
+  Description: "Checks for calls to puts, print, etc."
+  Enabled: true
+
+Rails/ReadWriteAttribute:
+  Description: "Checks for read_attribute(:attr) and write_attribute(:attr, val)."
+  Enabled: true
+
+Rails/ScopeArgs:
+  Description: "Checks the arguments of ActiveRecord scopes."
+  Enabled: true
+
+Rails/Validation:
+  Description: "Use sexy validations."
+  Enabled: true
diff --git a/.sun-ci.yml b/.sun-ci.yml
index bfe5f3d..40abbc8 100644
--- a/.sun-ci.yml
+++ b/.sun-ci.yml
@@ -8,16 +8,16 @@ jobs:
     image: sunci/ruby:3.2.2
     script:
       - cp database-ci.yml config/database.yml
-      - bundle _2.5.23_ install --path vendor/bundle
+      - bundle _2.1.4_ install --path vendor/bundle # _2.1.4_ if ruby 2.7.1 or 3.0.2
     cache:
-      key: vendor_$CI_COMMIT_REF_NAME
-      paths:
-        - vendor/bundle
+      - key: vendor_$CI_BRANCH
+        paths:
+          - vendor/bundle
   - name: test:rspec
     stage: test
     image: sunci/ruby:3.2.2
     services:
-      - image: mysql:5.7.20
+      - image: mysql:5.7.22
         name: mysql-test
         environment:
           MYSQL_DATABASE: db-test
@@ -25,15 +25,14 @@ jobs:
           MYSQL_PASSWORD: password-test
           MYSQL_ROOT_PASSWORD: password-test
     before_script:
-      - bundle _2.5.23_ install --path vendor/bundle
+      - bundle _2.1.4_ install --path vendor/bundle # _2.1.4_ if ruby 2.7.1 or 3.0.2
     script:
       - RAILS_ENV=test bundle exec rails db:drop db:create db:migrate
-      - bundle _2.5.23_ exec rspec
-
+      - bundle exec rspec # _2.1.4_ if ruby 2.7.1 or 3.0.2
   - name: test:rubocop
     stage: test
     image: sunci/ruby:3.2.2
     before_script:
-      - bundle _2.5.23_ install --path vendor/bundle
+      - bundle _2.1.4_ install --path vendor/bundle # _2.1.4_ if ruby 2.7.1 or 3.0.2
     script:
       - bundle exec rubocop --require rubocop/formatter/checkstyle_formatter --format RuboCop::Formatter::CheckstyleFormatter --no-color app/ lib/
diff --git a/Gemfile b/Gemfile
index f6a53ea..e75bbf4 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,31 +1,30 @@
 source "https://rubygems.org"
 
 gem "bcrypt", "~> 3.1.7"
+gem "bootsnap", require: false
 gem "bootstrap-sass", "3.4.1"
 gem "config"
 gem "faker"
-gem "rails", "~> 7.2.2"
-gem "sprockets-rails"
+gem "i18n"
+gem "importmap-rails"
+gem "jbuilder"
 gem "mysql2", "~> 0.5"
-gem "puma", ">= 5.0"
 gem "pagy"
-gem "importmap-rails"
-gem "i18n"
-gem "turbo-rails"
-gem "stimulus-rails"
+gem "puma", ">= 5.0"
+gem "rails", "~> 7.2.2"
 gem "sassc-rails", "2.1.2"
-gem "jbuilder"
-gem "tzinfo-data", platforms: %i[ mswin mswin64 mingw x64_mingw jruby ]
-
-gem "bootsnap", require: false
-
+gem "sprockets-rails"
+gem "stimulus-rails"
+gem "turbo-rails"
+gem "tzinfo-data", platforms: %i(mswin mswin64 mingw x64_mingw jruby)
 
 group :development, :test do
-  gem "debug", platforms: %i[ mri mswin mswin64 mingw x64_mingw ], require: "debug/prelude"
-
   gem "brakeman", require: false
-
-  gem "rubocop-rails-omakase", require: false
+  gem "debug", platforms: %i(mri mingw x64_mingw)
+  gem "rspec-rails"
+  gem "rubocop", "~> 1.26", require: false
+  gem "rubocop-checkstyle_formatter", require: false
+  gem "rubocop-rails", "~> 2.14.0", require: false
 end
 
 group :development do
diff --git a/Gemfile.lock b/Gemfile.lock
index f4f4643..9d4daeb 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -110,18 +110,13 @@ GEM
       irb (~> 1.10)
       reline (>= 0.3.8)
     deep_merge (1.2.2)
+    diff-lcs (1.5.1)
     drb (2.2.1)
     erubi (1.13.0)
     execjs (2.10.0)
     faker (3.5.1)
       i18n (>= 1.8.11, < 2)
-    ffi (1.17.0)
-    ffi (1.17.0-aarch64-linux-gnu)
-    ffi (1.17.0-arm-linux-gnu)
-    ffi (1.17.0-arm64-darwin)
-    ffi (1.17.0-x86-linux-gnu)
-    ffi (1.17.0-x86_64-darwin)
-    ffi (1.17.0-x86_64-linux-gnu)
+    ffi (1.17.1)
     globalid (1.2.1)
       activesupport (>= 6.1)
     i18n (1.14.6)
@@ -237,6 +232,23 @@ GEM
     reline (0.5.12)
       io-console (~> 0.5)
     rexml (3.3.9)
+    rspec-core (3.13.2)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.3)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-rails (7.1.0)
+      actionpack (>= 7.0)
+      activesupport (>= 7.0)
+      railties (>= 7.0)
+      rspec-core (~> 3.13)
+      rspec-expectations (~> 3.13)
+      rspec-mocks (~> 3.13)
+      rspec-support (~> 3.13)
+    rspec-support (3.13.2)
     rubocop (1.69.1)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)
@@ -249,22 +261,12 @@ GEM
       unicode-display_width (>= 2.4.0, < 4.0)
     rubocop-ast (1.36.2)
       parser (>= 3.3.1.0)
-    rubocop-minitest (0.36.0)
-      rubocop (>= 1.61, < 2.0)
-      rubocop-ast (>= 1.31.1, < 2.0)
-    rubocop-performance (1.23.0)
-      rubocop (>= 1.48.1, < 2.0)
-      rubocop-ast (>= 1.31.1, < 2.0)
-    rubocop-rails (2.27.0)
+    rubocop-checkstyle_formatter (0.6.0)
+      rubocop (>= 1.14.0)
+    rubocop-rails (2.14.2)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
-      rubocop (>= 1.52.0, < 2.0)
-      rubocop-ast (>= 1.31.1, < 2.0)
-    rubocop-rails-omakase (1.0.0)
-      rubocop
-      rubocop-minitest
-      rubocop-performance
-      rubocop-rails
+      rubocop (>= 1.7.0, < 2.0)
     ruby-progressbar (1.13.0)
     rubyzip (2.3.2)
     sassc (2.4.0)
@@ -342,7 +344,10 @@ DEPENDENCIES
   pagy
   puma (>= 5.0)
   rails (~> 7.2.2)
-  rubocop-rails-omakase
+  rspec-rails
+  rubocop (~> 1.26)
+  rubocop-checkstyle_formatter
+  rubocop-rails (~> 2.14.0)
   sassc-rails (= 2.1.2)
   selenium-webdriver
   sprockets-rails
diff --git a/app/assets/stylesheets/_variables.scss b/app/assets/stylesheets/_variables.scss
index 77f8721..88689e3 100644
--- a/app/assets/stylesheets/_variables.scss
+++ b/app/assets/stylesheets/_variables.scss
@@ -1,9 +1,10 @@
 $gray-light: #777;
 $gray-medium-light: #eaeaea;
-$gray-medium-light: #eaeaea;
 $border-color: #bbb;
 $state-danger-text: red;
 $white: #ffffff;
+$background-comment: #f1f1f1;
+$time-step: #999;
 
 @mixin box_sizing {
   -moz-box-sizing:    border-box;
diff --git a/app/assets/stylesheets/custom.scss b/app/assets/stylesheets/custom.scss
index 6af02a2..14c0f88 100644
--- a/app/assets/stylesheets/custom.scss
+++ b/app/assets/stylesheets/custom.scss
@@ -130,3 +130,72 @@ input {
   background: rgba(0, 0, 0, 0.5);
   z-index: 1000;
 }
+
+/* Comments */
+.chat-container {
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+}
+
+.chat-comments {
+  max-height: 300px;
+  overflow-y: auto;
+}
+
+.chat-comment {
+  display: flex;
+  margin-bottom: 15px;
+}
+
+.chat-comment.sent {
+  justify-content: flex-end;
+}
+
+.chat-comment.received {
+  justify-content: flex-start;
+}
+
+.comment-content {
+  max-width: 70%;
+  background-color: $background-comment;
+  padding: 10px;
+  border-radius: 5px;
+  position: relative;
+}
+
+.chat-comment .avatar {
+  margin-right: 10px;
+}
+
+.chat-comment .avatar-img {
+  width: 35px;
+  height: 35px;
+  border-radius: 50%;
+}
+
+.username {
+  font-weight: bold;
+}
+
+.text {
+  margin-top: 5px;
+}
+
+.timestamp {
+  font-size: 0.8em;
+  color: $time-step;
+  position: absolute;
+  bottom: 5px;
+  right: 10px;
+}
+
+.chat-input {
+  margin-top: 20px;
+}
+
+.comments--box {
+  border-radius: 10px;
+  border: solid 1px;
+  padding: 5px;
+}
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 2f0027e..4d55bfd 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -1,8 +1,18 @@
 class ApplicationController < ActionController::Base
   include SessionsHelper
   include Pagy::Backend
+  rescue_from Exception, with: :render_not_found
+
+  private
+  def render_not_found _exception
+    render plain: "404 Not Found", status: :not_found
+  end
 
   def logged_in_user
-    logged_in?
+    return if logged_in?
+
+    store_location
+    flash[:danger] = t "user.please_login"
+    redirect_to login_url, status: :see_other
   end
 end
diff --git a/app/controllers/comments_controller.rb b/app/controllers/comments_controller.rb
new file mode 100644
index 0000000..8d9b3e1
--- /dev/null
+++ b/app/controllers/comments_controller.rb
@@ -0,0 +1,41 @@
+class CommentsController < ApplicationController
+  before_action :set_task
+  before_action :set_comment, only: %i(destroy)
+
+  def create
+    @comment = @task.comments.build comment_params
+    @comment.sender = current_user
+
+    if @comment.save
+      redirect_to @task
+    else
+      flash[:alert] = t "tasks.comment.failed_to_add_comment"
+    end
+  end
+
+  def destroy
+    if @comment.destroy
+      flash[:success] = t "tasks.comment.comment_deleted_successfully"
+    else
+      flash[:alert] = t "tasks.comment.failed_to_delete_comment"
+    end
+    redirect_to @task
+  end
+
+  private
+
+  def comment_params
+    params.require(:comment).permit Comment::COMMENT_PERMITTED_ATTRIBUTES
+  end
+
+  def set_task
+    @task = Task.find params[:task_id]
+  rescue ActiveRecord::RecordNotFound
+    flash[:alert] = t "tasks.not_found"
+    redirect_to tasks_path
+  end
+
+  def set_comment
+    @comment = @task.comments.find params[:id]
+  end
+end
diff --git a/app/controllers/sessions_controller.rb b/app/controllers/sessions_controller.rb
index 3076d52..3f44b58 100644
--- a/app/controllers/sessions_controller.rb
+++ b/app/controllers/sessions_controller.rb
@@ -3,23 +3,28 @@ def new; end
 
   def create
     user = User.find_by email: params[:session][:email].downcase
-    if user&.authenticate params[:session][:password]
-      forwarding_url = session[:forwarding_url]
-      reset_session
+    return unless user&.authenticate params[:session][:password]
 
-      if params[:session][:remember_me] == "1"
-        remember(user)
-      else
-        forget(user)
-      end
-
-      log_in user
-      redirect_to forwarding_url || root_url
-    end
+    handle_remember_me(user)
+    log_in user
+    forwarding_url = session[:forwarding_url]
+    redirect_to forwarding_url || root_url
   end
 
   def destroy
     log_out if logged_in?
+    flash[:success] = t "user.logout_successfully"
     redirect_to login_path, status: :see_other
   end
+
+  private
+
+  def handle_remember_me user
+    reset_session
+    if params[:session][:remember_me] == "1"
+      remember(user)
+    else
+      forget(user)
+    end
+  end
 end
diff --git a/app/controllers/tasks_controller.rb b/app/controllers/tasks_controller.rb
index 0711f99..b41f560 100644
--- a/app/controllers/tasks_controller.rb
+++ b/app/controllers/tasks_controller.rb
@@ -1,16 +1,23 @@
 class TasksController < ApplicationController
-  before_action :set_task, only: %i[edit update destroy]
-  before_action :logged_in_user, only: %i[create edit destroy]
-  before_action :set_categories, :set_user, :available_users, only: %i[new index create edit]
+  before_action :set_task, only: %i(edit update destroy)
+  before_action :logged_in_user, only: %i(create edit destroy)
+  before_action :set_categories, :set_user, :available_users,
+                only: %i(new index create edit)
+  before_action :set_comment, only: %i(edit)
 
   def new
     @task = Task.new
   end
 
   def index
-    @tasks = current_user.mentor_role? ? Task.by_mentor_and_mentees(current_user.id) : current_user.tasks
+    @tasks = if current_user.mentor_role?
+               Task.by_mentor_and_mentees current_user.id
+             else
+               Task.by_naitei current_user.id
+             end
 
-    @pagy, @tasks = pagy @tasks, limit: Settings.default.max_tasks_per_page_5
+    @pagy, @tasks =
+      pagy @tasks, limit: Settings.default.max_tasks_per_page_5
   end
 
   def create
@@ -25,7 +32,8 @@ def create
 
   def edit
     @subtasks = @task.subtasks
-    @pagy, @subtasks = pagy @subtasks, limit: Settings.default.max_tasks_per_page_5
+    @pagy, @subtasks =
+      pagy @subtasks, limit: Settings.default.max_tasks_per_page_5
   end
 
   def update
@@ -65,10 +73,14 @@ def set_task
   end
 
   def available_users
-    @users = current_user.mentor_role? ? current_user.mentees : [ current_user ]
+    @users = current_user.mentor_role? ? current_user.mentees : [current_user]
   end
 
   def set_categories
     @categories = current_user.categories
   end
+
+  def set_comment
+    @comments = @task.comments
+  end
 end
diff --git a/app/helpers/comments_helper.rb b/app/helpers/comments_helper.rb
new file mode 100644
index 0000000..6a1588e
--- /dev/null
+++ b/app/helpers/comments_helper.rb
@@ -0,0 +1,15 @@
+module CommentsHelper
+  def comment_user comment, current_user
+    comment.sender == current_user ? :sent : :received
+  end
+
+  def comment_delete_button comment, task
+    return unless comment.sender == current_user
+
+    button_to t("tasks.comment.delete"),
+              task_comment_path(task, comment),
+              method: :delete,
+              data: {confirm: t("tasks.comment.confirm_delete")},
+              class: "btn btn-danger btn-sm"
+  end
+end
diff --git a/app/helpers/tasks_helper.rb b/app/helpers/tasks_helper.rb
index b815fe5..505a7ed 100644
--- a/app/helpers/tasks_helper.rb
+++ b/app/helpers/tasks_helper.rb
@@ -12,20 +12,10 @@ def task_table_headers
   end
 
   def priority_options
-    Task.priorities.keys.map { |p| [ p.humanize, p ] }
+    Task.priorities.keys.map{|p| [p.humanize, p]}
   end
 
   def status_options
-    Task.statuses.keys.map { |s| [ s.humanize, s ] }
-  end
-
-  def assignee_select(f, task, users, current_user)
-    if current_user.mentor_role?
-      f.select :assignee_id, options_from_collection_for_select(users, :id, :name, task.assignee_id), { include_blank: t("tasks.select_assignee") }, class: "form-control"
-    elsif current_user.naitei_role?
-      f.select :assignee_id, options_from_collection_for_select([ current_user ], :id, :name, task.assignee_id), { include_blank: t("tasks.select_assignee") }, class: "form-control"
-    else
-      f.select :assignee_id, [], { include_blank: t("tasks.select_assignee") }, class: "form-control"
-    end
+    Task.statuses.keys.map{|s| [s.humanize, s]}
   end
 end
diff --git a/app/jobs/application_job.rb b/app/jobs/application_job.rb
index d394c3d..a009ace 100644
--- a/app/jobs/application_job.rb
+++ b/app/jobs/application_job.rb
@@ -1,7 +1,2 @@
 class ApplicationJob < ActiveJob::Base
-  # Automatically retry jobs that encountered a deadlock
-  # retry_on ActiveRecord::Deadlocked
-
-  # Most jobs are safe to ignore if the underlying records are no longer available
-  # discard_on ActiveJob::DeserializationError
 end
diff --git a/app/models/activity.rb b/app/models/activity.rb
index 210ddf0..bc6cab4 100644
--- a/app/models/activity.rb
+++ b/app/models/activity.rb
@@ -3,5 +3,7 @@ class Activity < ApplicationRecord
   belongs_to :task, optional: true
 
   validates :action, presence: true
-  validates :description, length: { maximum: Settings.default.comment_max_length_10_000 }, allow_blank: true
+  validates :description,
+            length: {maximum: Settings.default.comment_max_length_10_000},
+            allow_blank: true
 end
diff --git a/app/models/category.rb b/app/models/category.rb
index d685e01..5c7f6a7 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -2,5 +2,6 @@ class Category < ApplicationRecord
   belongs_to :user
   has_many :tasks, dependent: :destroy
 
-  validates :name, presence: true, length: { maximum: Settings.default.category_max_length_255 }
+  validates :name, presence: true,
+            length: {maximum: Settings.default.category_max_length_255}
 end
diff --git a/app/models/comment.rb b/app/models/comment.rb
index a0721cf..b469be9 100644
--- a/app/models/comment.rb
+++ b/app/models/comment.rb
@@ -1,6 +1,8 @@
 class Comment < ApplicationRecord
   belongs_to :task
-  belongs_to :user
+  belongs_to :sender, class_name: "User", foreign_key: "user_id"
+  COMMENT_PERMITTED_ATTRIBUTES = %i(content).freeze
 
-  validates :content, presence: true, length: { maximum: Settings.default.comment_max_length_10_000 }
+  validates :content, presence: true,
+            length: {maximum: Settings.default.comment_max_length_10_000}
 end
diff --git a/app/models/task.rb b/app/models/task.rb
index 5554d42..d0d8394 100644
--- a/app/models/task.rb
+++ b/app/models/task.rb
@@ -2,28 +2,62 @@ class Task < ApplicationRecord
   belongs_to :user
   belongs_to :category, optional: true
   belongs_to :parent_task, class_name: "Task", optional: true
-  has_many :subtasks, class_name: "Task", foreign_key: :parent_task_id, dependent: :destroy
+  has_many :subtasks, class_name: "Task",
+           foreign_key: :parent_task_id, dependent: :destroy
   has_many :comments, dependent: :destroy
   has_many :activities, dependent: :destroy
 
   enum priority: Settings.default.priorities.to_h.transform_keys(&:to_sym)
   enum status: Settings.default.status.to_h.transform_keys(&:to_sym)
 
-  validates :title, presence: true, length: { maximum: Settings.default.task_title_max_length }
+  validates :title, presence: true,
+            length: {maximum: Settings.default.task_title_max_length}
   validates :priority, presence: true
   validates :status, presence: true
-  validates :deadline, comparison: { greater_than: :start_date, allow_blank: true }, if: :start_date?
-  TASK_PERMITTED_ATTRIBUTES = %i[title description priority status start_date deadline category_id assignee_id].freeze
-  SUBTASK_PERMITTED_ATTRIBUTES = %i[title description priority status start_date deadline category_id assignee_id parent_task_id].freeze
+  validates :deadline,
+            comparison: {greater_than: :start_date, allow_blank: true},
+            if: :start_date?
 
-  scope :by_naitei, ->(user_id) { where("user_id = :user_id OR assignee_id = :user_id", user_id: user_id) }
-  scope :by_mentor_and_mentees, ->(mentor_id) {
+  TASK_PERMITTED_ATTRIBUTES = %i(
+    title description priority status start_date
+    deadline category_id assignee_id
+  ).freeze
+
+  SUBTASK_PERMITTED_ATTRIBUTES = %i(
+    title description priority status start_date
+    deadline category_id assignee_id parent_task_id
+  ).freeze
+
+  scope :by_naitei, lambda {|user_id|
+    where(
+      "parent_task_id IS NULL
+      AND (user_id = :user_id OR assignee_id = :user_id)",
+      user_id: user_id
+    )
+  }
+  scope :by_mentor_and_mentees, lambda {|mentor_id|
     joins("LEFT JOIN users AS mentees ON mentees.id = tasks.assignee_id")
-    .where("tasks.user_id = :mentor_id OR mentees.mentor_id = :mentor_id", mentor_id: mentor_id)
+      .where(
+        "parent_task_id IS NULL
+        AND (tasks.user_id = :mentor_id OR mentees.mentor_id = :mentor_id)",
+        mentor_id: mentor_id
+      )
+  }
+  scope :by_priority, lambda {|priority|
+    where("parent_task_id IS NULL AND priority = ?", priorities[priority])
+  }
+  scope :by_status, lambda {|status|
+    where("parent_task_id IS NULL AND status = ?", statuses[status])
+  }
+  scope :filter_by_category, lambda {|category|
+    if category.present?
+      where("parent_task_id IS NULL AND category_id = ?", category)
+    end
+  }
+  scope :filter_by_status, lambda {|status|
+    where("parent_task_id IS NULL AND status = ?", status) if status.present?
+  }
+  scope :filter_by_deadline, lambda {|deadline|
+    where("deadline <= ?", deadline) if deadline.present?
   }
-  scope :by_priority, ->(priority) { where(priority: priorities[priority]) }
-  scope :by_status, ->(status) { where(status: statuses[status]) }
-  scope :filter_by_category, ->(category) { where(category_id: category) if category.present? }
-  scope :filter_by_status, ->(status) { where(status: status) if status.present? }
-  scope :filter_by_deadline, ->(deadline) { where("deadline <= ?", deadline) if deadline.present? }
 end
diff --git a/app/models/user.rb b/app/models/user.rb
index f715322..6eb7f89 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -5,23 +5,29 @@ class User < ApplicationRecord
 
   attr_accessor :remember_token, :activation_token, :reset_token
 
-  USER_PERMITTED_ATTRIBUTES = %i[name email password].freeze
+  USER_PERMITTED_ATTRIBUTES = %i(name email password).freeze
 
   has_many :tasks, dependent: :destroy
-  has_many :mentees, class_name: "User", foreign_key: :mentor_id, dependent: :nullify
+  has_many :mentees, class_name: "User",
+          foreign_key: :mentor_id, dependent: :nullify
   belongs_to :mentor, class_name: "User", optional: true
-  has_many :created_tasks, class_name: "Task", foreign_key: :creator_id, dependent: :destroy
-  has_many :assigned_tasks, class_name: "Task", foreign_key: :assignee_id, dependent: :nullify
+  has_many :created_tasks, class_name: "Task",
+          foreign_key: :creator_id, dependent: :destroy
+  has_many :assigned_tasks, class_name: "Task",
+          foreign_key: :assignee_id, dependent: :nullify
   has_many :categories, dependent: :destroy
   has_many :activities, dependent: :destroy
   has_many :comments, dependent: :destroy
   has_many :task_participants, dependent: :destroy
-  has_many :participated_tasks, through: :task_participants, source: :task
 
-  enum role: Settings.default.roles.to_h.transform_keys(&:to_sym), _suffix: true
-
-  validates :email, presence: true, uniqueness: true, format: { with: URI::MailTo::EMAIL_REGEXP }
-  validates :name, presence: true, length: { maximum: Settings.default.username_max_length_100 }
+  enum role: Settings.default.roles.to_h.transform_keys(&:to_sym),
+       _suffix: true
+  validates :email,
+            presence: true,
+            uniqueness: true,
+            format: {with: URI::MailTo::EMAIL_REGEXP}
+  validates :name, presence: true,
+          length: {maximum: Settings.default.username_max_length_100}
   validates :role, presence: true
 
   before_save :downcase_email
@@ -34,9 +40,9 @@ def new_token
     def digest string
       cost = if ActiveModel::SecurePassword.min_cost
                BCrypt::Engine::MIN_COST
-      else
-        BCrypt::Engine.cost
-      end
+             else
+               BCrypt::Engine.cost
+             end
       BCrypt::Password.create(string, cost:)
     end
   end
@@ -47,7 +53,7 @@ def remember
     remember_digest
   end
 
-  def authenticated?(attribute, token)
+  def authenticated? attribute, token
     digest = send "#{attribute}_digest"
     return false if digest.nil?
 
diff --git a/app/views/comments/_chat.html.erb b/app/views/comments/_chat.html.erb
new file mode 100644
index 0000000..307d65b
--- /dev/null
+++ b/app/views/comments/_chat.html.erb
@@ -0,0 +1,18 @@
+<h3><%= t "tasks.comment.comments" %></h3>
+
+<div class="chat-comments">
+  <% if @comments.present? %>
+    <% @comments.each do |comment| %>
+      <%= render partial: "comments/comment", locals: { comment: comment, current_user: current_user, task: @task } %>
+    <% end %>
+  <% else %>
+    <p><%= t "tasks.comment.no_comments_yet" %></p>
+  <% end %>
+</div>
+
+<div class="chat-input">
+  <%= form_with(model: [@task, @task.comments.build], local: true) do |form| %>
+    <%= form.text_area :content, placeholder: t("tasks.comment.type_your_comment"), class: "form-control", rows: 3, required: true %>
+    <%= form.submit t("tasks.comment.send"), class: "btn btn-primary mt-2" %>
+  <% end %>
+</div>
diff --git a/app/views/comments/_comment.html.erb b/app/views/comments/_comment.html.erb
new file mode 100644
index 0000000..93b2284
--- /dev/null
+++ b/app/views/comments/_comment.html.erb
@@ -0,0 +1,8 @@
+<div class="chat-comment <%= comment_user(comment, current_user) %>">
+  <div class="comment-content">
+    <div class="username"><%= comment.sender.name %></div>
+    <div class="text"><%= comment.content %></div>
+    <div class="timestamp"><%= comment.created_at.strftime("%H:%M") %></div>
+  </div>
+  <%= comment_delete_button(comment, @task) %>
+</div>
diff --git a/app/views/shared/_form_fields.html.erb b/app/views/shared/_form_fields.html.erb
index 7b1d127..72b8be9 100644
--- a/app/views/shared/_form_fields.html.erb
+++ b/app/views/shared/_form_fields.html.erb
@@ -24,7 +24,8 @@
 </div>
 
 <div class="mb-4">
-  <%= assignee_select(f, @task, @users, @user) %>
+  <%= f.label :assignee_id, t("tasks.assignee"), class: "form-label fw-bold" %>
+  <%= f.select :assignee_id, options_from_collection_for_select(@users, :id, :name, @task.assignee_id), { include_blank: t("tasks.select_assignee") }, class: "form-control" %>
 </div>
 
 <div class="row mb-4">
diff --git a/app/views/tasks/edit.html.erb b/app/views/tasks/edit.html.erb
index c901084..6521a86 100644
--- a/app/views/tasks/edit.html.erb
+++ b/app/views/tasks/edit.html.erb
@@ -1,29 +1,37 @@
 <% provide :title, @task.title %>
 <h1><%= t "tasks.update.title" %></h1>
 
-<div class="task_form">
-  <%= render "task_form" %>
+<div>
+  <div class="col-md-8 task_form">
+    <%= render "task_form" %>
 
-  <div class="add-subtask">
-    <% unless @task.parent_task %>
-      <button id="add-subtask-btn" class="btn btn-primary">
-        <%= t("tasks.edit.add_new_subtask") %>
-      </button>
+    <div class="add-subtask">
+      <% unless @task.parent_task %>
+        <button id="add-subtask-btn" class="btn btn-primary">
+          <%= t("tasks.edit.add_new_subtask") %>
+        </button>
 
-      <% if @subtasks.present? && @subtasks.any? %>
-        <%= render "task_table", tasks: @subtasks, pagy: @pagy %>
-      <% else %>
-        <p><%= t("tasks.index.messages.no_subtasks") %></p>
-      <% end %>
+        <% if @subtasks.present? && @subtasks.any? %>
+          <%= render "task_table", tasks: @subtasks, pagy: @pagy %>
+        <% else %>
+          <p><%= t("tasks.index.messages.no_subtasks") %></p>
+        <% end %>
 
-      <div id="subtask-popup" class="popup" style="display: none;">
-        <div class="popup-content">
-          <span class="close" id="close-popup">&times;</span>
-          <%= render "subtask_form", task: @subtask, parent_task_id: @task.id %>
+        <div id="subtask-popup" class="popup" style="display: none;">
+          <div class="popup-content">
+            <span class="close" id="close-popup">&times;</span>
+            <%= render "subtask_form", task: @subtask, parent_task_id: @task.id %>
+          </div>
         </div>
-      </div>
 
-      <div class="overlay" id="overlay" style="display: none;"></div>
-    <% end %>
+        <div class="overlay" id="overlay" style="display: none;"></div>
+      <% end %>
+    </div>
+  </div>
+
+   <div class="col-md-4 comments-logs">
+    <div class="comments--box">
+      <%= render "comments/chat", comments: @comments, current_user: current_user %>
+    </div>
   </div>
 </div>
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 12078f4..5cf03fa 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -10,6 +10,7 @@ en:
     new_users: "New to the site?"
     signup: "Sign up"
   user:
+    logout_successfully: "Logout successfully"
     please_check_your_mail: "Please check your mail"
     please_login: "Please login"
     you_sure: "You sure"
@@ -67,3 +68,14 @@ en:
     new:
       title: "New Task"
       subtask_created_successfully: "Subtask created successfully!"
+
+    comment:
+        failed_to_add_comment: "Failed to add comment."
+        failed_to_delete_comment: "Failed to delete comment."
+        comment_deleted_successfully: "Comment deleted successfully."
+        comments: "Comments"
+        no_comments_yet: "No comments yet."
+        confirrm_delete: "Are you sure you want to delete this comment?"
+        type_your_comment: "Type your comment..."
+        send: "Send"
+        delete: "Delete"
diff --git a/config/locales/vi.yml b/config/locales/vi.yml
new file mode 100644
index 0000000..4af52ab
--- /dev/null
+++ b/config/locales/vi.yml
@@ -0,0 +1,81 @@
+vi:
+  application:
+    base_title: "Todollo"
+  header:
+    login: "Đăng nhập"
+  login:
+    email: "Email"
+    password: "Mật khẩu"
+    remember_me: "Nhớ tôi"
+    new_users: "Mới đến trang web?"
+    signup: "Đăng ký"
+  user:
+    logout_successfully: "Đăng xuất thành công"
+    please_check_your_mail: "Vui lòng kiểm tra email của bạn"
+    please_login: "Vui lòng đăng nhập"
+    you_sure: "Bạn chắc chứ?"
+  static_pages:
+    home:
+      title: "Trang chủ"
+  tasks:
+    task_deleted: "Xóa nhiệm vụ thành công!"
+    task_create_successfully: "Tạo nhiệm vụ thành công!"
+    failed_to_delete_the_task: "Xóa nhiệm vụ không thành công"
+    not_found: "Không tìm thấy"
+    title: "Tiêu đề"
+    enter_title: "Nhập tiêu đề..."
+    description: "Mô tả"
+    enter_description: "Nhập mô tả..."
+    enter_assignee: "Nhập người được giao..."
+    priority: "Độ ưu tiên"
+    select_priority: "Chọn độ ưu tiên"
+    status: "Trạng thái"
+    select_status: "Chọn trạng thái"
+    assignee: "Người được giao"
+    start_date: "Ngày bắt đầu"
+    deadline: "Thời hạn"
+    save: "Lưu"
+    select_category: "Chọn danh mục"
+    index:
+      title: "Danh sách Nhiệm vụ"
+      filter:
+        search_placeholder: "Tìm kiếm"
+        all_categories: "Tất cả Danh mục"
+        all_statuses: "Tất cả Trạng thái"
+        pending: "Đang chờ"
+        in_progress: "Đang tiến hành"
+        completed: "Đã hoàn thành"
+        expired: "Đã hết hạn"
+        filter_button: "Lọc"
+        create_task_button: "Tạo Nhiệm vụ"
+      table:
+        created_at: "Ngày tạo"
+        deadline: "Thời hạn"
+        title: "Tiêu đề"
+        category: "Danh mục"
+        status: "Trạng thái"
+        actions: "Hành động"
+        update: "Cập nhật"
+        delete: "Xóa"
+      messages:
+        no_tasks: "Không tìm thấy nhiệm vụ nào."
+        no_subtasks: "Không có nhiệm vụ con"
+
+    update:
+      title: "Cập nhật Nhiệm vụ"
+      successfully_updated: "Cập nhật thành công"
+
+    new:
+      title: "Nhiệm vụ Mới"
+      subtask_created_successfully: "Tạo nhiệm vụ con thành công!"
+
+    comment:
+        failed_to_add_comment: "Thêm bình luận không thành công."
+        failed_to_delete_comment: "Xóa bình luận không thành công."
+        comment_deleted_successfully: "Bình luận đã được xóa thành công."
+        comments: "Bình luận"
+        no_comments_yet: "Chưa có bình luận nào."
+        confirrm_delete: "Bạn có chắc chắn muốn xóa bình luận này không?"
+        type_your_comment: "Nhập bình luận của bạn..."
+        send: "Gửi"
+        delete: "Xóa"
diff --git a/config/routes.rb b/config/routes.rb
index 3df508f..2721db7 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -6,8 +6,9 @@
   get "users/edit"
   get "login", to: "sessions#new"
   post "login", to: "sessions#create"
-  get "logout", to: "sessions#destroy"
+  delete "logout", to: "sessions#destroy"
   resources :tasks, only: %i[new index edit destroy create update] do
     resources :subtasks, only: %i[create]
+    resources :comments, only: %i[create destroy]
   end
 end
diff --git a/db/migrate/20241204235032_create_users.rb b/db/migrate/20241203035032_create_users.rb
similarity index 100%
rename from db/migrate/20241204235032_create_users.rb
rename to db/migrate/20241203035032_create_users.rb
diff --git a/db/migrate/20241204035901_create_categories.rb b/db/migrate/20241203035901_create_categories.rb
similarity index 100%
rename from db/migrate/20241204035901_create_categories.rb
rename to db/migrate/20241203035901_create_categories.rb
diff --git a/db/migrate/20241212043229_update_tasks_and_task_participants.rb b/db/migrate/20241212043229_update_tasks_and_task_participants.rb
index f289d11..d72ad26 100644
--- a/db/migrate/20241212043229_update_tasks_and_task_participants.rb
+++ b/db/migrate/20241212043229_update_tasks_and_task_participants.rb
@@ -1,10 +1,4 @@
 class UpdateTasksAndTaskParticipants < ActiveRecord::Migration[7.0]
   def change
-    remove_column :tasks, :creator_id, :bigint
-    remove_column :tasks, :assignee_id, :bigint
-
-    add_column :task_participants, :role, :string, null: false, default: 'assignee'
-
-    add_index :task_participants, %i[task_id role], unique: true, where: "role = 'creator'"
   end
 end
diff --git a/db/migrate/20250109065827_add_unique_index_to_users_email.rb b/db/migrate/20250109065827_add_unique_index_to_users_email.rb
new file mode 100644
index 0000000..fe87965
--- /dev/null
+++ b/db/migrate/20250109065827_add_unique_index_to_users_email.rb
@@ -0,0 +1,5 @@
+class AddUniqueIndexToUsersEmail < ActiveRecord::Migration[7.2]
+  def change
+    add_index :users, :email, unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index d119255..de636c5 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2025_01_08_025849) do
+ActiveRecord::Schema[7.2].define(version: 2025_01_09_065827) do
   create_table "activities", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "user_id", null: false
     t.bigint "task_id", null: false
@@ -40,6 +40,16 @@
     t.index ["user_id"], name: "index_comments_on_user_id"
   end
 
+  create_table "task_participants", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "task_id", null: false
+    t.bigint "user_id", null: false
+    t.integer "role"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["task_id"], name: "index_task_participants_on_task_id"
+    t.index ["user_id"], name: "index_task_participants_on_user_id"
+  end
+
   create_table "tasks", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "title"
     t.text "description"
@@ -69,6 +79,7 @@
     t.boolean "activated"
     t.datetime "activated_at"
     t.integer "mentor_id"
+    t.index ["email"], name: "index_users_on_email", unique: true
   end
 
   add_foreign_key "activities", "tasks"
@@ -76,6 +87,8 @@
   add_foreign_key "categories", "users"
   add_foreign_key "comments", "tasks"
   add_foreign_key "comments", "users"
+  add_foreign_key "task_participants", "tasks"
+  add_foreign_key "task_participants", "users"
   add_foreign_key "tasks", "categories"
   add_foreign_key "tasks", "tasks", column: "parent_task_id"
 end
diff --git a/db/seeds.rb b/db/seeds.rb
index 2a21e9f..599be57 100644
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -1,23 +1,23 @@
 # Create Users
 admin = User.create!(
-  email: 'admin@example.com',
-  password: 'password123',
-  name: 'Admin User',
-  role: 'supervisor'
+  email: "admin@example.com",
+  password: "password123",
+  name: "Admin User",
+  role: "mentor"
 )
 
 user = User.create!(
-  email: 'user@example.com',
-  password: 'password123',
-  name: 'Regular User',
-  role: 'mentor'
+  email: "user@example.com",
+  password: "password123",
+  name: "Regular User",
+  role: "naitei"
 )
 
 # Create Categories
 categories = [
-  Category.create!(name: 'Development', user_id: admin.id),
-  Category.create!(name: 'Design', user_id: user.id),
-  Category.create!(name: 'Management', user_id: admin.id)
+  Category.create!(name: "Development", user_id: admin.id),
+  Category.create!(name: "Design", user_id: user.id),
+  Category.create!(name: "Management", user_id: admin.id)
 ]
 
 # Create Tasks