diff --git a/README.md b/README.md
index 31a1dc1..2a4074f 100644
--- a/README.md
+++ b/README.md
@@ -40,13 +40,13 @@ Web Application Basic of Yii Version 2. <a href="http://www.yiiframework.com/" t
 ```text
 root
 ├── config                  
-│   ├── Common              Common configuration.
+│   ├── common              Common configuration.
 │   │   ├── components.php  
 │   │   └── container.php   
-│   ├── Console             Console configuration.
+│   ├── console             Console configuration.
 │   │   ├── app.php
 │   │   └── components.php     
-│   ├── Web                 Web configuration.
+│   ├── web                 Web configuration.
 │   │   ├── app.php
 │   │   ├── bootstrap.php    
 │   │   ├── components.php
@@ -59,19 +59,18 @@ root
 │   ├── params-web.php      Web parameters.
 │   └── params.php          Common parameters.
 ├── src             
-│   ├── Framework 
-│   │   ├── Asset           Asset bundle files.
-│   │   ├── EnventHandler   Event handler files.
-│   │   └── resources 
+│   ├── framework 
+│   │   ├── asset           Asset bundle files.
+│   │   ├── event           Event handler files.
+│   │   └── resource 
 │   │       ├── css         Css files.
 │   │       ├── js          Js files.
 │   │       ├── layout      Layout files.
 │   │       └── message     Translation files.
-│   └── UseCase
-│       ├── Contact         Contact use case.
-│       ├── Hello           Hello use case (console).
-│       └── Site            Site use case.
-│           └── About       About use case.
+│   └── usecase
+│       ├── contact         Contact use case.
+│       ├── hello           Hello use case (console).
+│       └── site            Site use case.
 ├── tests                   Tests codeception.
 ├── vendor                  Composer dependencies.
 └── public                  Web server public.
diff --git a/composer.json b/composer.json
index eead50b..4100960 100644
--- a/composer.json
+++ b/composer.json
@@ -14,11 +14,8 @@
     "require": {
         "php": ">=8.2",
         "php-forge/foxy": "^0.1",
-        "sjaakp/yii2-icon": "^1.0",
         "ui-awesome/html": "^0.3",
         "ui-awesome/html-component-bootstrap5": "^1.0@dev",
-        "ui-awesome/html-core":"^0.1",
-        "ui-awesome/html-helper":"^0.2",
         "ui-awesome/html-svg":"^0.2",
         "yii2-extensions/localeurls": "dev-main",
         "yiisoft/config": "^1.4",
@@ -45,12 +42,12 @@
     },
     "autoload": {
         "psr-4": {
-            "App\\": "src/"
+            "app\\": "src/"
         }
     },
     "autoload-dev": {
         "psr-4": {
-            "App\\Tests\\": "tests/"
+            "app\\tests\\": "tests/"
         }
     },
     "extra": {
diff --git a/config/params-console.php b/config/params-console.php
index c92620a..0e6983a 100644
--- a/config/params-console.php
+++ b/config/params-console.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-use App\UseCase\Hello\HelloController;
+use app\usecase\hello\HelloController;
 use yii\console\controllers\ServeController;
 
 $rootDir = dirname(__DIR__);
diff --git a/config/params-web.php b/config/params-web.php
index 6befc1c..7cfe514 100644
--- a/config/params-web.php
+++ b/config/params-web.php
@@ -2,8 +2,8 @@
 
 declare(strict_types=1);
 
-use App\UseCase\Contact\ContactController;
-use App\UseCase\Site\SiteController;
+use app\usecase\contact\ContactController;
+use app\usecase\site\SiteController;
 
 return [
     // web application settings shared
@@ -59,7 +59,6 @@
             ],
         ],
         'app.menu.islogged' => [],
-        'icons' => '@npm/@fortawesome/fontawesome-free/svgs/{family}/{name}.svg',
     ],
     'web.request.cookieValidationKey' => 'your-cookie-validation-key',
     'web.request.enableCsrfValidation' => true,
diff --git a/config/params.php b/config/params.php
index 94b80d7..d8ffb63 100644
--- a/config/params.php
+++ b/config/params.php
@@ -7,7 +7,7 @@
 return [
     'common.aliases' => [
         '@app' => $rootDir,
-        '@resource' => '@app/src/Framework/resource',
+        '@resource' => '@app/src/framework/resource',
     ],
     'common.bootstrap' => ['log'],
     'common.log.levels' => ['error', 'warning', 'info'],
diff --git a/config/web/bootstrap.php b/config/web/bootstrap.php
index a63a611..09ffbac 100644
--- a/config/web/bootstrap.php
+++ b/config/web/bootstrap.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-use App\Framework\EventHandler\ContactEventHandler;
+use app\framework\event\ContactEventHandler;
 
 return [
     'bootstrap' => [
diff --git a/ecs.php b/ecs.php
index dc1fcae..2b9a33f 100644
--- a/ecs.php
+++ b/ecs.php
@@ -54,4 +54,10 @@
             SingleQuoteFixer::class,
         ]
     )
-    ->withSkip(['*/src/UseCase/Contact/view/*', '*/src/UseCase/Site/view/*']);
+    ->withSkip(
+        [
+            '*/src/framework/resource/layout/*',
+            '*/src/usecase/contact/view/*',
+            '*/src/usecase/site/view/*',
+        ],
+    );
diff --git a/src/Framework/resource/layout/component/footer-icons.php b/src/Framework/resource/layout/component/footer-icons.php
deleted file mode 100644
index 609c74e..0000000
--- a/src/Framework/resource/layout/component/footer-icons.php
+++ /dev/null
@@ -1,66 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use UIAwesome\Html\{Graphic\Svg, Textual\A};
-
-$linkIconDefinitions = [
-    'class()' => ['d-none d-sm-block d-md-block d-lg-block d-xl-block text-muted hover:text-dark text-decoration-none ms-3'],
-    'rel()' => ['noopener'],
-    'target()' => ['_blank'],
-];
-
-$svgDefinitions = [
-    'fill()' => ['currentColor'],
-    'height()' => ['32'],
-];
-
-// Github icon
-echo A::widget($linkIconDefinitions)
-    ->class('md:block hidden')
-    ->content(
-        Svg::widget($svgDefinitions)
-            ->filePath(Yii::getAlias('@npm/@fortawesome/fontawesome-free/svgs/brands/github.svg')),
-    )
-    ->href('https://github.com/yiisoft')
-    ->title('GitHub');
-
-// Slack icon
-echo A::widget($linkIconDefinitions)
-    ->class('md:block hidden')
-    ->content(
-        Svg::widget($svgDefinitions)
-            ->filePath(Yii::getAlias('@npm/@fortawesome/fontawesome-free/svgs/brands/slack.svg')),
-    )
-    ->href(
-        'https://join.slack.com/t/yii/shared_invite/enQtMzQ4MDExMDcyNTk2LTc0NDQ2ZTZhNjkzZDgwYjE4YjZlNGQxZjFmZDBjZTU3NjViMDE4ZTMxNDRkZjVlNmM1ZTA1ODVmZGUwY2U3NDA',
-    )
-    ->title('Slack');
-
-// Facebook icon
-echo A::widget($linkIconDefinitions)
-    ->class('md:block hidden')
-    ->content(
-        Svg::widget($svgDefinitions)
-            ->filePath(Yii::getAlias('@npm/@fortawesome/fontawesome-free/svgs/brands/facebook.svg')),
-    )
-    ->href('https://www.facebook.com/groups/yiitalk/')
-    ->title('Facebook');
-
-// Twitter icon
-echo A::widget($linkIconDefinitions)
-    ->content(
-        Svg::widget($svgDefinitions)
-            ->filePath(Yii::getAlias('@npm/@fortawesome/fontawesome-free/svgs/brands/twitter.svg')),
-    )
-    ->href('https://twitter.com/yiiframework')
-    ->title('Twitter');
-
-// Telegram icon
-echo A::widget($linkIconDefinitions)
-    ->content(
-        Svg::widget($svgDefinitions)
-            ->filePath(Yii::getAlias('@npm/@fortawesome/fontawesome-free/svgs/brands/telegram.svg')),
-    )
-    ->href('https://t.me/yii_framework_in_english')
-    ->title('Telegram');
diff --git a/src/Framework/resource/layout/component/toggle_language.php b/src/Framework/resource/layout/component/toggle_language.php
deleted file mode 100644
index cea71bd..0000000
--- a/src/Framework/resource/layout/component/toggle_language.php
+++ /dev/null
@@ -1,37 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use App\Framework\Asset\LocaleAsset;
-use UIAwesome\Html\Component\Bootstrap5\{Dropdown, Item};
-use yii\{helpers\Url, web\View};
-
-/**
- * @var string $languageLabel
- * @var View $this
- */
-LocaleAsset::register($this);
-
-$items = [];
-
-$locales = Yii::$app->params['app.localeurls.languages'] ?? [];
-
-foreach ($locales as $key => $value) {
-    $icon = match ($key) {
-        'en' => 'us',
-        'zh' => 'cn',
-        default => $key,
-    };
-
-    if (Yii::$app->language === $value) {
-        $languageLabel = "site.selector.language.$key";
-    }
-
-    $items[] = Item::widget()
-        ->iconClass('fi fi-' . $icon . ' fis me-2')
-        ->label(Yii::t('app.basic', "site.selector.language.$key"))
-        ->link(Url::current(['language' => $key]))
-        ->active(Yii::$app->language === $value);
-}
-
-echo Dropdown::widget()->cookbook('language')->items(...$items);
diff --git a/src/Framework/resource/layout/footer.php b/src/Framework/resource/layout/footer.php
deleted file mode 100644
index 93d9b0a..0000000
--- a/src/Framework/resource/layout/footer.php
+++ /dev/null
@@ -1,46 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use App\Framework\Asset\ToggleThemeAsset;
-use UIAwesome\Html\{
-    Component\Bootstrap5\Toggle,
-    Group\Div,
-    Semantic\Footer,
-    Textual\A,
-    Textual\Span
-};
-use yii\web\View;
-
-/**
- * @var View $this
- */
-ToggleThemeAsset::register($this);
-echo Div::widget()
-    ->class('container mt-auto')
-    ->content(
-        Footer::widget()
-            ->class('d-flex justify-content-between align-items-center py-3 my-4 border-top border-secondary-subtle')
-            ->content(
-                Div::widget()->class('col-md-4')
-                    ->content(
-                        A::widget()
-                            ->ariaLabel('Yii Framework')
-                            ->class('mb-3 mb-md-0 text-body-secondary text-decoration-none lh-1')
-                            ->content(
-                                Span::widget()
-                                    ->class('mb-3 mb-md-0 text-body-secondary')
-                                    ->content('&copy;', date('Y'), ' <strong>YiiFramework™.</strong>'),
-                            )
-                            ->href('https://www.yiiframework.com/')
-                            ->title('Yii Framework'),
-                    ),
-                Div::widget()
-                    ->class('col-md-4 justify-content-end d-flex align-items-center')
-                    ->content(
-                        $this->render('component/footer-icons'),
-                        Toggle::Widget()->cookbook('selector-theme')->id('theme-toggle'),
-                        $this->render('component/toggle_language'),
-                    ),
-            ),
-    );
diff --git a/src/Framework/resource/layout/head.php b/src/Framework/resource/layout/head.php
deleted file mode 100644
index cd8f701..0000000
--- a/src/Framework/resource/layout/head.php
+++ /dev/null
@@ -1,18 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use UIAwesome\Html\{Document\Head, Metadata\Meta, Metadata\Title};
-use yii\{helpers\Html, web\View};
-
-/**
- * @var View $this
- */
-?>
-<?= Head::widget()->begin() ?>
-    <?= Meta::widget()->charset(Yii::$app->charset) ?>
-    <?= Meta::widget()->content('width=device-width, initial-scale=1')->name('viewport') ?>
-    <?= Html::csrfMetaTags() ?>
-    <?= Title::widget()->content(Html::encode($this->title)) ?>
-    <?php $this->head() ?>
-<?= Head::end();
diff --git a/src/Framework/resource/layout/main.php b/src/Framework/resource/layout/main.php
deleted file mode 100644
index 8280ebd..0000000
--- a/src/Framework/resource/layout/main.php
+++ /dev/null
@@ -1,39 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use App\Framework\Asset\AppAsset;
-use sjaakp\icon\Icon;
-use UIAwesome\Html\{Document\Body, Document\Html, Group\Div, Semantic\Header};
-use yii\{bootstrap5\Breadcrumbs, web\View};
-
-/**
- * @var string $content
- * @var View $this
- */
-AppAsset::register($this);
-?>
-<?php $this->beginPage() ?>
-    <!DOCTYPE html>
-    <?= Html::widget()->attributes(['lang' => Yii::$app->language, 'data-bs-theme' => 'auto'])->begin() ?>
-        <?= $this->render('head') ?>
-        <?php $this->beginBody() ?>
-            <?= Body::widget()->class('d-flex')->begin() ?>
-                <?= Div::widget()->class('cover-container d-flex w-100 h-100 mx-auto flex-column')->begin() ?>
-                    <?= Header::widget()->class('mb-auto')->begin() ?>
-                        <?= $this->render('component/menu') ?>
-                        <?= $this->render('component/alert') ?>
-                        <?= Breadcrumbs::widget(
-                            [
-                                'links' => $this->params['breadcrumbs'] ?? [],
-                            ],
-                        ) ?>
-                    <?= Header::end() ?>
-                    <?= $content ?>
-                    <?= $this->render('footer') ?>
-                <?= Div::end() ?>
-                <?= Icon::symbols($this) ?>
-            <?= Body::end() ?>
-        <?php $this->endBody() ?>
-    <?= Html::end() ?>
-<?php $this->endPage();
diff --git a/src/UseCase/Contact/view/index.php b/src/UseCase/Contact/view/index.php
deleted file mode 100644
index 51eed69..0000000
--- a/src/UseCase/Contact/view/index.php
+++ /dev/null
@@ -1,135 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use App\UseCase\Contact\ContactForm;
-use UIAwesome\Html\{FormControl\Input\Submit, Group\Div, Group\Hr, Group\P, Helper\Encode, Semantic\H};
-use yii\{bootstrap5\ActiveForm, captcha\Captcha, symfonymailer\Mailer, web\Session, web\View};
-
-/**
- * @var ContactForm $model
- * @var Mailer $mailer
- * @var Session $session
- * @var View $this
- */
-$this->title = $this->title = Yii::t('app.basic', 'Contact');
-$tabInput = 1;
-?>
-<?= Div::widget()->class('container mt-3')->begin() ?>
-    <?= Div::widget()->class('row align-items-center justify-content-center')->begin() ?>
-        <?= Div::widget()->class('col-md-5 col-sm-12')->begin() ?>
-            <?=
-                Div::widget()
-                    ->class('bg-body-tertiary shadow border-0 rounded border-light p-4 p-lg-5 w-100 fmxw-500')
-                    ->begin()
-            ?>
-                <?= H::widget()->content(Encode::content($this->title))->class('fw-bold')->tagName('h1') ?>
-                <?= P::widget()->content(Yii::t('app.basic', 'Please fill out the following form to contact us.')) ?>
-                <?= Hr::widget()->class('mb-3') ?>
-                <?php $form = ActiveForm::begin(
-                    [
-                        'id' => 'contact-form',
-                        'layout' => ActiveForm::LAYOUT_FLOATING,
-                    ]
-                ) ?>
-                    <?=
-                        $form->field($model, 'name')
-                            ->textInput(
-                                [
-                                    'autofocus' => true,
-                                    'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Username Here') .'")',
-                                    'required' => true,
-                                    'tabindex' => $tabInput++,
-                                ]
-                            )
-                    ?>
-                    <?=
-                        $form->field($model, 'email')
-                            ->textInput(
-                                [
-                                    'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Email Here') . '")',
-                                    'required' => true,
-                                    'tabindex' => $tabInput++,
-                                ]
-                            )
-                    ?>
-                    <?=
-                        $form->field($model, 'subject')
-                            ->textInput(
-                                [
-                                    'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Subject Here').'")',
-                                    'required' => true,
-                                    'tabindex' => $tabInput++,
-                                ]
-                            )
-                    ?>
-                    <?=
-                        $form->field($model, 'body')
-                            ->textarea(
-                                [
-                                    'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Body Here') . '")',
-                                    'required' => true,
-                                    'style' => 'height: 100px',
-                                    'tabindex' => $tabInput++,
-                                ]
-                            )
-                    ?>
-                    <?=
-                        $form->field($model, 'verifyCode', ['labelOptions' => ['id' => 'verifyCode']])
-                            ->widget(
-                                Captcha::class,
-                                [
-                                    'captchaAction' => 'contact/captcha',
-                                    'template' => '{input}<div class="text-center mt-3 mb-3">' . '<b>' . Yii::t('app.basic', 'Captcha Code') . ': ' . '</b>' . '{image}</div>',
-                                    'options' => [
-                                        'class' => 'form-control',
-                                        'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Captcha Code Here') . '")',
-                                        'required' => true,
-                                        'tabindex' => $tabInput++,
-                                    ],
-                                ]
-                            )
-                    ?>
-                    <?=
-                        Div::widget()
-                            ->class('d-grid gap-2')
-                            ->content(
-                                Submit::widget()
-                                    ->class('btn btn-lg btn-primary btn-block')
-                                    ->name('contact-button')
-                                    ->tabIndex($tabInput++)
-                                    ->value(Yii::t('app.basic', 'Contact us'))
-                        )
-                    ?>
-                <?php ActiveForm::end() ?>
-            <?= Div::end() ?>
-        <?= Div::end() ?>
-    <?= Div::end() ?>
-    <?= P::widget()->class('text-center mt-5')->begin() ?>
-        <?php if ($session->hasFlash('contactFormSubmitted')) : ?>
-            <?= Hr::widget() ?>
-            <?= P::widget()->class('text-center')->begin() ?>
-                <?= Yii::t(
-                    'app.basic',
-                    'Note that if you turn on the Yii debugger, you should be able to view the mail message on the mail panel of the debugger.'
-                ) ?>
-                <br/>
-                <br/>
-                <?php if ($mailer->useFileTransport) : ?>
-                    <?= Yii::t(
-                        'app.basic',
-                        'Because the application is in development mode, the email is not sent but saved as a file under.'
-                    ) ?>
-                    <br/>
-                    <?= '<code>' . Yii::getAlias($mailer->fileTransportPath) . '</code>' ?>
-                    <br/>
-                    <br/>
-                    <?= Yii::t(
-                        'app.basic',
-                        'Please configure the <code>useFileTransport </code>property of the <code>mail </code>application component to be false to enable email sending.'
-                    ) ?>
-                <?php endif ?>
-            <?= P::end() ?>
-        <?php endif ?>
-    <?= P::end() ?>
-<?= Div::end();
diff --git a/src/UseCase/Site/view/404.php b/src/UseCase/Site/view/404.php
deleted file mode 100644
index c5e9c5b..0000000
--- a/src/UseCase/Site/view/404.php
+++ /dev/null
@@ -1,43 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use UIAwesome\Html\{Group\Div, Helper\Encode, Multimedia\Img, Semantic\H};
-use yii\web\View;
-
-/**
- * @var string $message
- * @var string $name
- * @var View $this
- */
-$this->title = $name;
-
-echo Div::widget()
-    ->class('d-flex flex-column align-items-center justify-center')
-    ->content(
-        Div::widget()
-            ->class('text-center mb-3')
-            ->content(
-                Img::widget()
-                    ->alt('404')
-                    ->class('img-fluid mb-4')
-                    ->src(
-                        'https://raw.githubusercontent.com/yii-tools/.github/61bbcb1b1f777740cce4200f95ae4bc0aa4350a8/images/app/404.svg',
-                    )
-            ),
-        Div::widget()
-            ->class('text-center mb-3')
-            ->content(
-                H::widget()->class('mb-4')->content(Encode::content($this->title))->tagName('h1'),
-                H::widget()
-                    ->content(
-                        Encode::content(Yii::t('app.basic', 'Oops! Looks like you followed a bad link.'))
-                    )
-                    ->tagName('h6'),
-                H::widget()
-                    ->content(
-                        Encode::content(Yii::t('app.basic', 'If you think this is a problem with us, please tell us.'))
-                    )
-                    ->tagName('h6'),
-            ),
-    );
diff --git a/src/UseCase/Site/view/about.php b/src/UseCase/Site/view/about.php
deleted file mode 100644
index d9a8812..0000000
--- a/src/UseCase/Site/view/about.php
+++ /dev/null
@@ -1,23 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use UIAwesome\Html\{Core\HTMLBuilder, Group\Div, Group\P, Helper\Encode, Semantic\H};
-use yii\web\View;
-
-/** @var View $this */
-$this->title = Yii::t('app.basic', 'About');
-
-echo Div::widget()
-    ->class('text-center')
-    ->content(
-        H::widget()->content(Encode::content($this->title))->class('mb-40 display-4 fw-bold')->tagName('h1'),
-        P::widget()
-            ->content(
-                Yii::t(
-                    'app.basic',
-                    'This is the About page. You may modify the following file to customize its content.',
-                ),
-            ),
-        HTMLBuilder::createTag('code', __FILE__),
-    );
diff --git a/src/UseCase/Site/view/index.php b/src/UseCase/Site/view/index.php
deleted file mode 100644
index 70065fc..0000000
--- a/src/UseCase/Site/view/index.php
+++ /dev/null
@@ -1,21 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use UIAwesome\Html\{Group\Div, Group\P, Helper\Encode, Semantic\H};
-use yii\web\View;
-
-/** @var View $this */
-$this->title = Yii::t('app.basic', 'Index');
-
-echo Div::widget()
-    ->class('jumbotron jumbotron-fluid text-center')
-    ->content(
-        H::widget()
-            ->class('display-2 fw-bold')
-            ->content(Encode::content(Yii::t('app.basic', 'Web Application')))
-            ->tagName('h1'),
-        P::widget()
-            ->class('lead fw-bold')
-            ->content(Encode::content(Yii::t('app.basic', 'Yii v.22'))),
-    );
diff --git a/src/Framework/Asset/AppAsset.php b/src/framework/asset/AppAsset.php
similarity index 66%
rename from src/Framework/Asset/AppAsset.php
rename to src/framework/asset/AppAsset.php
index 1040770..587a559 100644
--- a/src/Framework/Asset/AppAsset.php
+++ b/src/framework/asset/AppAsset.php
@@ -2,16 +2,11 @@
 
 declare(strict_types=1);
 
-namespace App\Framework\Asset;
+namespace app\framework\asset;
 
-use yii\bootstrap5\BootstrapAsset;
-use yii\bootstrap5\BootstrapPluginAsset;
-use yii\web\AssetBundle;
-use yii\web\YiiAsset;
+use yii\bootstrap5\{BootstrapAsset, BootstrapPluginAsset};
+use yii\web\{AssetBundle, YiiAsset};
 
-/**
- * Asset bundle for the web application.
- **/
 final class AppAsset extends AssetBundle
 {
     public $sourcePath = __DIR__ . '/../resource/';
diff --git a/src/Framework/Asset/LocaleAsset.php b/src/framework/asset/LocaleAsset.php
similarity index 82%
rename from src/Framework/Asset/LocaleAsset.php
rename to src/framework/asset/LocaleAsset.php
index 2bd6b3a..54b40ea 100644
--- a/src/Framework/Asset/LocaleAsset.php
+++ b/src/framework/asset/LocaleAsset.php
@@ -2,13 +2,10 @@
 
 declare(strict_types=1);
 
-namespace App\Framework\Asset;
+namespace app\framework\asset;
 
 use yii\web\AssetBundle;
 
-/**
- * Asset bundle for locale urls.
- **/
 final class LocaleAsset extends AssetBundle
 {
     public $sourcePath = '@npm/flag-icons/';
diff --git a/src/Framework/Asset/ToggleThemeAsset.php b/src/framework/asset/ToggleThemeAsset.php
similarity index 75%
rename from src/Framework/Asset/ToggleThemeAsset.php
rename to src/framework/asset/ToggleThemeAsset.php
index 53c4737..c950609 100644
--- a/src/Framework/Asset/ToggleThemeAsset.php
+++ b/src/framework/asset/ToggleThemeAsset.php
@@ -2,15 +2,11 @@
 
 declare(strict_types=1);
 
-namespace App\Framework\Asset;
+namespace app\framework\asset;
 
 use yii\bootstrap5\BootstrapAsset;
-use yii\web\AssetBundle;
-use yii\web\View;
+use yii\web\{AssetBundle, View};
 
-/**
- * Asset bundle for the toggle theme.
- **/
 final class ToggleThemeAsset extends AssetBundle
 {
     public $sourcePath = __DIR__ . '/../resource/js/';
diff --git a/src/Framework/EventHandler/ContactEventHandler.php b/src/framework/event/ContactEventHandler.php
similarity index 79%
rename from src/Framework/EventHandler/ContactEventHandler.php
rename to src/framework/event/ContactEventHandler.php
index edcec03..9a3085d 100644
--- a/src/Framework/EventHandler/ContactEventHandler.php
+++ b/src/framework/event/ContactEventHandler.php
@@ -2,13 +2,11 @@
 
 declare(strict_types=1);
 
-namespace App\Framework\EventHandler;
+namespace app\framework\event;
 
-use App\UseCase\Contact\ContactEvent;
-use App\UseCase\Contact\Index\IndexAction;
+use app\usecase\contact\{ContactEvent, IndexAction};
 use Yii;
-use yii\base\BootstrapInterface;
-use yii\base\Event;
+use yii\base\{BootstrapInterface, Event};
 use yii\web\Application;
 
 final class ContactEventHandler implements BootstrapInterface
diff --git a/src/Framework/resource/css/site.css b/src/framework/resource/css/site.css
similarity index 100%
rename from src/Framework/resource/css/site.css
rename to src/framework/resource/css/site.css
diff --git a/src/Framework/resource/js/toggle-theme.js b/src/framework/resource/js/toggle-theme.js
similarity index 100%
rename from src/Framework/resource/js/toggle-theme.js
rename to src/framework/resource/js/toggle-theme.js
diff --git a/src/Framework/resource/layout/component/alert.php b/src/framework/resource/layout/component/alert.php
similarity index 74%
rename from src/Framework/resource/layout/component/alert.php
rename to src/framework/resource/layout/component/alert.php
index 422038d..cca6dca 100644
--- a/src/Framework/resource/layout/component/alert.php
+++ b/src/framework/resource/layout/component/alert.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-use UIAwesome\Html\{Component\Bootstrap5\Alert, Group\Div};
+use UIAwesome\Html\{Component\Bootstrap5\Alert};
 
 $session = Yii::$app->getSession();
 $flashMessages = $session->getAllFlashes();
@@ -13,5 +13,7 @@
         $html[] = Alert::widget()->cookbook('dismissible', $type)->content($message);
     }
 }
-
-echo Div::widget()->id('alert_dismissing')->content(...$html);
+?>
+<div id ="alert_dismissing">
+    <?= implode('', $html) ?>
+</div>
diff --git a/src/framework/resource/layout/component/footer-icons.php b/src/framework/resource/layout/component/footer-icons.php
new file mode 100644
index 0000000..365d0f5
--- /dev/null
+++ b/src/framework/resource/layout/component/footer-icons.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+use UIAwesome\Html\{Graphic\Svg};
+use yii\helpers\Html;
+
+$socialLinks = [
+    ['icon' => 'github.svg', 'url' => 'https://github.com/yiisoft', 'title' => 'GitHub'],
+    ['icon' => 'slack.svg', 'url' => 'https://join.slack.com/t/yii/shared_invite/...', 'title' => 'Slack'],
+    ['icon' => 'facebook.svg', 'url' => 'https://www.facebook.com/groups/yiitalk/', 'title' => 'Facebook'],
+    ['icon' => 'twitter.svg', 'url' => 'https://twitter.com/yiiframework', 'title' => 'Twitter'],
+    ['icon' => 'telegram.svg', 'url' => 'https://t.me/yii_framework_in_english', 'title' => 'Telegram'],
+];
+
+foreach ($socialLinks as $link): ?>
+    <?= Html::a(
+        Svg::widget()
+            ->attributes(['height' => '24', 'width' => '24'])
+            ->filePath(Yii::getAlias('@npm/bootstrap-icons/icons/' . $link['icon']))
+            ->render(),
+        $link['url'],
+        [
+            'class' => 'd-none d-sm-block d-md-block d-lg-block d-xl-block text-muted text-decoration-none ms-3',
+            'rel' => 'noopener',
+            'title' => $link['title'],
+        ],
+    ) ?>
+<?php endforeach;
diff --git a/src/Framework/resource/layout/component/menu.php b/src/framework/resource/layout/component/menu.php
similarity index 100%
rename from src/Framework/resource/layout/component/menu.php
rename to src/framework/resource/layout/component/menu.php
diff --git a/src/framework/resource/layout/component/toggle_language.php b/src/framework/resource/layout/component/toggle_language.php
new file mode 100644
index 0000000..4e31e7d
--- /dev/null
+++ b/src/framework/resource/layout/component/toggle_language.php
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+use app\framework\asset\LocaleAsset;
+use UIAwesome\Html\Graphic\Svg;
+use yii\helpers\Html;
+use yii\{helpers\Url, web\View};
+
+/**
+ * @var View $this
+ */
+LocaleAsset::register($this);
+
+$languageLabel = 'site.selector.language.en';
+$items = [];
+
+$locales = Yii::$app->params['app.localeurls.languages'] ?? [];
+
+foreach ($locales as $key => $value) {
+    $icon = match ($key) {
+        'en' => 'us',
+        'zh' => 'cn',
+        default => $key,
+    };
+
+    if (Yii::$app->language === $value) {
+        $languageLabel = "site.selector.language.$key";
+    }
+
+    $items[] = Html::a(
+        '<i class="fi fi-' . $icon . ' fis me-2"></i> ' . Yii::t('app.basic', $languageLabel),
+        Url::current(['language' => $key]),
+        [
+            'class' => 'dropdown-item d-flex align-items-center' . (Yii::$app->language === $value ? ' active' : ''),
+        ],
+    );
+}
+?>
+<div class="btn-group dropup">
+    <?= Html::button(
+        Svg::widget()
+            ->attributes(['height' => '24', 'width' => '24'])
+            ->class('w-3 h-3')
+            ->filePath(Yii::getAlias('@npm/bootstrap-icons/icons/globe.svg'))
+            ->render(),
+        [
+            'aria-expanded' => 'true',
+            'aria-label' => 'Toggle language dropdown',
+            'class' => 'btn btn-primary dropdown-toggle d-flex align-items-center text-white show',
+            'data-bs-toggle' => 'dropdown',
+            'title' => 'Select language',
+            'type' => 'button',
+        ],
+    ) ?>
+    <div id="dropdown-language">
+        <?= Html::ul(
+            $items,
+            [
+                'class' => 'dropdown-menu dropdown-menu-end shadow',
+                'encode' => false,
+            ],
+        ) ?>
+    </div>
+</div>
diff --git a/src/framework/resource/layout/component/toggle_theme.php b/src/framework/resource/layout/component/toggle_theme.php
new file mode 100644
index 0000000..2033334
--- /dev/null
+++ b/src/framework/resource/layout/component/toggle_theme.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+use UIAwesome\Html\Graphic\Svg;
+use yii\helpers\Html;
+
+?>
+<?= Html::button(
+    Svg::widget()
+        ->attributes(['height' => '24', 'width' => '24'])
+        ->filePath(Yii::getAlias('@npm/bootstrap-icons/icons/moon-stars.svg'))
+        ->id('theme-light-icon')
+        ->render() .
+    Svg::widget()
+        ->attributes(['height' => '24', 'width' => '24'])
+        ->filePath(Yii::getAlias('@npm/bootstrap-icons/icons/sun.svg'))
+        ->id('theme-dark-icon')
+        ->render(),
+    [
+        'class' => 'btn ms-2 me-2',
+        'id' => 'theme-toggle',
+        'type' => 'button',
+        'title' => 'Switch light/dark mode',
+    ],
+) ?>
diff --git a/src/framework/resource/layout/footer.php b/src/framework/resource/layout/footer.php
new file mode 100644
index 0000000..7f86619
--- /dev/null
+++ b/src/framework/resource/layout/footer.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+use app\framework\asset\ToggleThemeAsset;
+use yii\helpers\Html;
+use yii\web\View;
+
+/**
+ * @var View $this
+ */
+ToggleThemeAsset::register($this);
+?>
+
+<div class="container mt-auto">
+    <footer class ="d-flex justify-content-between align-items-center py-3 my-4 border-top border-secondary-subtle">
+        <div class="col-md-4">
+            <?= Html::a(
+                'Yii Framework' .
+                Html::tag(
+                    'span',
+                    '&copy;' . date('Y') . ' <strong>YiiFramework™.</strong>',
+                    [
+                        'class' => 'mb-3 mb-md-0 text-body-secondary',
+                    ],
+                ),
+                'https://www.yiiframework.com/',
+                [
+                    'aria-label' => 'Yii Framework',
+                    'class' => 'mb-3 mb-md-0 text-body-secondary text-decoration-none lh-1',
+                    'title' => 'Yii Framework',
+                ],
+            ) ?>
+        </div>
+        <div class="col-md-4 justify-content-end d-flex align-items-center">
+            <?= $this->render('component/footer-icons') ?>
+            <?= $this->render('component/toggle_theme') ?>
+            <?= $this->render('component/toggle_language') ?>
+        </div>
+    </footer>
+</div>
diff --git a/src/framework/resource/layout/head.php b/src/framework/resource/layout/head.php
new file mode 100644
index 0000000..d56a3f2
--- /dev/null
+++ b/src/framework/resource/layout/head.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+use yii\{helpers\Html, web\View};
+
+/**
+ * @var View $this
+ */
+?>
+<head>
+    <meta charset="<?= Yii::$app->charset ?>">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <?= Html::csrfMetaTags() ?>
+    <title><?= Html::encode($this->title) ?></title>
+    <?php $this->head() ?>
+</head>
diff --git a/src/framework/resource/layout/main.php b/src/framework/resource/layout/main.php
new file mode 100644
index 0000000..2c1be80
--- /dev/null
+++ b/src/framework/resource/layout/main.php
@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+use app\framework\asset\AppAsset;
+use yii\{bootstrap5\Breadcrumbs, web\View};
+
+/**
+ * @var string $content
+ * @var View $this
+ */
+AppAsset::register($this);
+?>
+<?php $this->beginPage() ?>
+    <!DOCTYPE html>
+    <html lang="<?= Yii::$app->language ?>" data-bs-theme="auto">
+        <?= $this->render('head') ?>
+        <body class="d-flex">
+            <?php $this->beginBody() ?>
+                <div class="cover-container d-flex w-100 h-100 mx-auto flex-column">
+                    <header class="mb-auto">
+                        <?= $this->render('component/menu') ?>
+                        <?= $this->render('component/alert') ?>
+                        <?= Breadcrumbs::widget(
+                            [
+                                'links' => $this->params['breadcrumbs'] ?? [],
+                            ],
+                        ) ?>
+                    </header>
+                    <?= $content ?>
+                    <?= $this->render('footer') ?>
+                </div>
+            <?php $this->endBody() ?>
+        </body>
+    </html>
+<?php $this->endPage();
diff --git a/src/Framework/resource/message/de/app.basic.php b/src/framework/resource/message/de/app.basic.php
similarity index 100%
rename from src/Framework/resource/message/de/app.basic.php
rename to src/framework/resource/message/de/app.basic.php
diff --git a/src/Framework/resource/message/en/app.basic.php b/src/framework/resource/message/en/app.basic.php
similarity index 100%
rename from src/Framework/resource/message/en/app.basic.php
rename to src/framework/resource/message/en/app.basic.php
diff --git a/src/Framework/resource/message/es/app.basic.php b/src/framework/resource/message/es/app.basic.php
similarity index 100%
rename from src/Framework/resource/message/es/app.basic.php
rename to src/framework/resource/message/es/app.basic.php
diff --git a/src/Framework/resource/message/fr/app.basic.php b/src/framework/resource/message/fr/app.basic.php
similarity index 100%
rename from src/Framework/resource/message/fr/app.basic.php
rename to src/framework/resource/message/fr/app.basic.php
diff --git a/src/Framework/resource/message/pt/app.basic.php b/src/framework/resource/message/pt/app.basic.php
similarity index 100%
rename from src/Framework/resource/message/pt/app.basic.php
rename to src/framework/resource/message/pt/app.basic.php
diff --git a/src/Framework/resource/message/ru/app.basic.php b/src/framework/resource/message/ru/app.basic.php
similarity index 100%
rename from src/Framework/resource/message/ru/app.basic.php
rename to src/framework/resource/message/ru/app.basic.php
diff --git a/src/Framework/resource/message/zh/app.basic.php b/src/framework/resource/message/zh/app.basic.php
similarity index 100%
rename from src/Framework/resource/message/zh/app.basic.php
rename to src/framework/resource/message/zh/app.basic.php
diff --git a/src/UseCase/Controller.php b/src/usecase/Controller.php
similarity index 96%
rename from src/UseCase/Controller.php
rename to src/usecase/Controller.php
index 4989468..3a9f5ea 100644
--- a/src/UseCase/Controller.php
+++ b/src/usecase/Controller.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase;
+namespace app\usecase;
 
 use yii\filters\VerbFilter;
 use yii\web\ErrorAction;
diff --git a/src/UseCase/Contact/ContactController.php b/src/usecase/contact/ContactController.php
similarity index 83%
rename from src/UseCase/Contact/ContactController.php
rename to src/usecase/contact/ContactController.php
index 77c1270..e0e89d6 100644
--- a/src/UseCase/Contact/ContactController.php
+++ b/src/usecase/contact/ContactController.php
@@ -2,13 +2,11 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase\Contact;
+namespace app\usecase\contact;
 
-use App\UseCase\Contact\Index\IndexAction;
-use App\UseCase\Controller;
+use app\usecase\Controller;
 use yii\captcha\CaptchaAction;
-
-use function array_merge;
+use yii\helpers\ArrayHelper;
 
 final class ContactController extends Controller
 {
@@ -19,7 +17,7 @@ final class ContactController extends Controller
 
     public function actions(): array
     {
-        return array_merge(
+        return ArrayHelper::merge(
             [
                 'index' => [
                     'class' => IndexAction::class,
diff --git a/src/UseCase/Contact/ContactEvent.php b/src/usecase/contact/ContactEvent.php
similarity index 83%
rename from src/UseCase/Contact/ContactEvent.php
rename to src/usecase/contact/ContactEvent.php
index bfd4267..aa97463 100644
--- a/src/UseCase/Contact/ContactEvent.php
+++ b/src/usecase/contact/ContactEvent.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase\Contact;
+namespace app\usecase\contact;
 
 use yii\base\Event;
 
diff --git a/src/UseCase/Contact/ContactForm.php b/src/usecase/contact/ContactForm.php
similarity index 98%
rename from src/UseCase/Contact/ContactForm.php
rename to src/usecase/contact/ContactForm.php
index c9c892f..3b20448 100644
--- a/src/UseCase/Contact/ContactForm.php
+++ b/src/usecase/contact/ContactForm.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase\Contact;
+namespace app\usecase\contact;
 
 use Yii;
 use yii\base\Model;
diff --git a/src/UseCase/Contact/Index/IndexAction.php b/src/usecase/contact/IndexAction.php
similarity index 87%
rename from src/UseCase/Contact/Index/IndexAction.php
rename to src/usecase/contact/IndexAction.php
index 1cff7ba..08a8848 100644
--- a/src/UseCase/Contact/Index/IndexAction.php
+++ b/src/usecase/contact/IndexAction.php
@@ -2,15 +2,11 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase\Contact\Index;
+namespace app\usecase\contact;
 
-use App\UseCase\Contact\ContactEvent;
-use yii\base\Action;
-use yii\base\InvalidConfigException;
+use yii\base\{Action, InvalidConfigException};
 use yii\symfonymailer\Mailer;
-use yii\web\Controller;
-use yii\web\Request;
-use yii\web\Session;
+use yii\web\{Controller, Request, Session};
 
 final class IndexAction extends Action
 {
diff --git a/src/usecase/contact/view/index.php b/src/usecase/contact/view/index.php
new file mode 100644
index 0000000..a6093c7
--- /dev/null
+++ b/src/usecase/contact/view/index.php
@@ -0,0 +1,119 @@
+<?php
+
+declare(strict_types=1);
+
+use app\usecase\contact\ContactForm;
+use yii\{bootstrap5\ActiveForm, captcha\Captcha, symfonymailer\Mailer, web\Session, web\View};
+use yii\helpers\Html;
+
+/**
+ * @var ContactForm $model
+ * @var Mailer $mailer
+ * @var Session $session
+ * @var View $this
+ */
+$this->title = Yii::t('app.basic', 'Contact');
+$tabInput = 1;
+?>
+<div class="container mt-3">
+    <div class="row align-items-center justify-content-center">
+        <div class="col-md-5 col-sm-12">
+            <div class="bg-body-tertiary shadow border-0 rounded border-light p-4 p-lg-5 w-100 fmxw-500">
+                <h1 class="fw-bold"><?= Html::encode($this->title) ?></h1>
+                <p><?= Yii::t('app.basic', 'Please fill out the following form to contact us.') ?></p>
+                <hr class="mb-3">
+                <?php $form = ActiveForm::begin(
+                    [
+                        'id' => 'contact-form',
+                        'layout' => ActiveForm::LAYOUT_FLOATING,
+                    ],
+                ) ?>
+                <?= $form->field($model, 'name')->textInput(
+                    [
+                        'autofocus' => true,
+                        'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Username Here') . '")',
+                        'required' => true,
+                        'tabindex' => $tabInput++,
+                    ],
+                ) ?>
+                <?= $form->field($model, 'email')->textInput(
+                    [
+                        'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Email Here') . '")',
+                        'required' => true,
+                        'tabindex' => $tabInput++,
+                    ],
+                ) ?>
+                <?= $form->field($model, 'subject')->textInput(
+                    [
+                        'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Subject Here') . '")',
+                        'required' => true,
+                        'tabindex' => $tabInput++,
+                    ],
+                ) ?>
+                <?= $form->field($model, 'body')->textarea(
+                    [
+                        'oninvalid' => 'this.setCustomValidity("' . Yii::t('app.basic', 'Enter Body Here') . '")',
+                        'required' => true,
+                        'style' => 'height: 100px',
+                        'tabindex' => $tabInput++,
+                    ],
+                ) ?>
+                <?= $form->field($model, 'verifyCode', ['labelOptions' => ['id' => 'verifyCode']])->widget(
+                    Captcha::class,
+                    [
+                        'captchaAction' => 'contact/captcha',
+                        'template' => '{input}<div class="text-center mt-3 mb-3">' . '<b>' .
+                        Yii::t('app.basic', 'Captcha Code') . ': ' . '</b>' . '{image}</div>',
+                        'options' => [
+                            'class' => 'form-control',
+                            'oninvalid' => 'this.setCustomValidity("' .
+                            Yii::t('app.basic', 'Enter Captcha Code Here') . '")',
+                            'required' => true,
+                            'tabindex' => $tabInput++,
+                        ],
+                    ],
+                ) ?>
+                <div class="d-grid gap-2">
+                    <?= Html::submitButton(
+                        Yii::t('app.basic', 'Contact us'),
+                        [
+                            'class' => 'btn btn-lg btn-primary btn-block',
+                            'name' => 'contact-button',
+                            'tabindex' => $tabInput++,
+                        ],
+                    ) ?>
+                <?php ActiveForm::end() ?>
+            </div>
+        </div>
+    </div>
+    <p class="text-center mt-5">
+        <?php if ($session->hasFlash('contactFormSubmitted')) : ?>
+            <hr>
+            <p class="text-success">
+                <?= Yii::t(
+                    'app.basic',
+                    'Note that if you turn on the Yii debugger, you should be able to view the mail message on the ' .
+                    'mail panel of the debugger.',
+                ) ?>
+                <br/>
+                <br/>
+                <?php if ($mailer->useFileTransport) : ?>
+                    <?= Yii::t(
+                        'app.basic',
+                        'Because the application is in development mode, the email is not sent but saved as a file ' .
+                        'under.',
+                    ) ?>
+                    <br/>
+                    <?= '<code>' . Yii::getAlias($mailer->fileTransportPath) . '</code>' ?>
+                    <br/>
+                    <br/>
+                    <?= Yii::t(
+                        'app.basic',
+                        'Please configure the <code>useFileTransport </code>property of the <code>mail ' .
+                        '</code>application component to be false to enable email sending.',
+                    ) ?>
+                <?php endif ?>
+            </p>
+        <?php endif ?>
+    </p>
+</div>
diff --git a/src/UseCase/Hello/HelloController.php b/src/usecase/hello/HelloController.php
similarity index 73%
rename from src/UseCase/Hello/HelloController.php
rename to src/usecase/hello/HelloController.php
index 0e96403..0f6944d 100644
--- a/src/UseCase/Hello/HelloController.php
+++ b/src/usecase/hello/HelloController.php
@@ -2,10 +2,9 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase\Hello;
+namespace app\usecase\hello;
 
-use yii\console\Controller;
-use yii\console\ExitCode;
+use yii\console\{Controller, ExitCode};
 
 final class HelloController extends Controller
 {
diff --git a/src/UseCase/Site/About/AboutAction.php b/src/usecase/site/AboutAction.php
similarity index 85%
rename from src/UseCase/Site/About/AboutAction.php
rename to src/usecase/site/AboutAction.php
index 77be102..df0aa02 100644
--- a/src/UseCase/Site/About/AboutAction.php
+++ b/src/usecase/site/AboutAction.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase\Site\About;
+namespace app\usecase\site;
 
 use yii\base\Action;
 
diff --git a/src/UseCase/Site/SiteController.php b/src/usecase/site/SiteController.php
similarity index 84%
rename from src/UseCase/Site/SiteController.php
rename to src/usecase/site/SiteController.php
index 7af21fd..59dc591 100644
--- a/src/UseCase/Site/SiteController.php
+++ b/src/usecase/site/SiteController.php
@@ -2,10 +2,9 @@
 
 declare(strict_types=1);
 
-namespace App\UseCase\Site;
+namespace app\usecase\site;
 
-use App\UseCase\Controller;
-use App\UseCase\Site\About\AboutAction;
+use app\usecase\Controller;
 use yii\web\ErrorAction;
 
 final class SiteController extends Controller
diff --git a/src/usecase/site/view/404.php b/src/usecase/site/view/404.php
new file mode 100644
index 0000000..30bec5a
--- /dev/null
+++ b/src/usecase/site/view/404.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+use yii\helpers\Html;
+use yii\web\View;
+
+/**
+ * @var string $name
+ * @var View $this
+ */
+$this->title = $name;
+?>
+<div class="d-flex flex-column align-items-center justify-center">
+    <div class="text-center mb-3">
+        <?= Html::img(
+            'https://raw.githubusercontent.com/yii-tools/.github/61bbcb1b1f777740cce4200f95ae4bc0aa4350a8/images/app/404.svg',
+            [
+                'alt' => '404',
+                'class' => 'img-fluid mb-4',
+            ],
+        ) ?>
+    </div>
+    <div class="text-center mb-3">
+        <h1 class="mb-4"><?= Html::encode($this->title) ?></h1>
+        <h6><?= Html::encode(Yii::t('app.basic', 'Oops! Looks like you followed a bad link.')) ?></h6>
+        <h6><?= Html::encode(Yii::t('app.basic', 'If you think this is a problem with us, please tell us.')) ?></h6>
+    </div>
+</div>
diff --git a/src/usecase/site/view/about.php b/src/usecase/site/view/about.php
new file mode 100644
index 0000000..2b6b16c
--- /dev/null
+++ b/src/usecase/site/view/about.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+use yii\helpers\Html;
+use yii\web\View;
+
+/** @var View $this */
+$this->title = Yii::t('app.basic', 'About');
+?>
+<div class="text-center">
+    <h1 class="mb-40 display-4 fw-bold"><?= Html::encode($this->title) ?></h1>
+    <p><?= Yii::t('app.basic', 'This is the About page. You may modify the following file to customize its content.') ?></p>
+    <code><?= __FILE__ ?></code>
+</div>
diff --git a/src/usecase/site/view/index.php b/src/usecase/site/view/index.php
new file mode 100644
index 0000000..a51ebbe
--- /dev/null
+++ b/src/usecase/site/view/index.php
@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+use yii\helpers\Html;
+use yii\web\View;
+
+/** @var View $this */
+$this->title = Yii::t('app.basic', 'Index');
+?>
+<div class="jumbotron jumbotron-fluid text-center">
+    <h1 class="display-2 fw-bold"><?= Yii::t('app.basic', 'Web Application') ?></h1>
+    <p class="lead fw-bold"><?= Yii::t('app.basic', 'Yii v.22') ?></p>
+    <?= Html::a(
+        Yii::t('app.basic', 'Get Started'),
+        'https://www.yiiframework.com/doc/',
+        [
+            'class' => 'btn btn-primary',
+        ],
+    ) ?>
+</div>
diff --git a/tests/Unit/HelloControllerTest.php b/tests/Unit/HelloControllerTest.php
index 88ab955..58fe88c 100644
--- a/tests/Unit/HelloControllerTest.php
+++ b/tests/Unit/HelloControllerTest.php
@@ -4,7 +4,7 @@
 
 namespace App\Tests\Unit;
 
-use App\UseCase\Hello\HelloController;
+use app\usecase\hello\HelloController;
 use Codeception\Test\Unit;
 use Yii;