diff --git a/CHANGELOG.md b/CHANGELOG.md
index cbab7e1..fe293fc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,12 @@
 All notable code changes to **Markdown Viewer** are documented here.
 Non-code commits (documentation, planning, README-only updates) are excluded.
 
+## v3.6.4
+
+- **Description:** Implemented Brazilian Portuguese (pt-BR) translation module. Localized all main editor labels, stats, tooltips, dialogs, placeholder, and search/replace options. Registered `hreflang` alternate link for Portuguese (pt-BR) search indexation and enabled automatic browser language detection fallback for Portuguese language preferences. Rotated Service Worker cache namespace to `v3.6.4` to trigger background cache updates.
+- **Date:** 2026-05-27
+- **URL:** https://github.com/ThisIs-Developer/Markdown-Viewer/commit/v3.6.4
+
 ---
 
 ## v3.6.3
diff --git a/desktop-app/resources/index.html b/desktop-app/resources/index.html
index 8740ec6..3bbeabf 100644
--- a/desktop-app/resources/index.html
+++ b/desktop-app/resources/index.html
@@ -18,6 +18,7 @@
     <link rel="alternate" hreflang="zh-Hans" href="https://markdownviewer.pages.dev/?lang=zh" />
     <link rel="alternate" hreflang="ja" href="https://markdownviewer.pages.dev/?lang=ja" />
     <link rel="alternate" hreflang="ko" href="https://markdownviewer.pages.dev/?lang=ko" />
+    <link rel="alternate" hreflang="pt-BR" href="https://markdownviewer.pages.dev/?lang=pt" />
 
     <!-- Asian Search Engine Verification Meta Tags -->
     <meta name="baidu-site-verification" content="baidu_verification_code_placeholder" />
@@ -190,6 +191,7 @@ <h1 class="h4 mb-0 me-2">Markdown Viewer</h1>
                             <li><a class="dropdown-item lang-select-item" href="#" data-lang="zh">🇨🇳 简体中文</a></li>
                             <li><a class="dropdown-item lang-select-item" href="#" data-lang="ja">🇯🇵 日本語</a></li>
                             <li><a class="dropdown-item lang-select-item" href="#" data-lang="ko">🇰🇷 한국어</a></li>
+                            <li><a class="dropdown-item lang-select-item" href="#" data-lang="pt">🇧🇷 Português (Brasil)</a></li>
                         </ul>
                     </div>
 
@@ -297,10 +299,11 @@ <h5>Menu</h5>
                                     <i class="bi bi-translate me-2"></i> Language: <span id="mobile-current-lang-label">English</span>
                                 </button>
                                 <ul class="dropdown-menu w-100" aria-labelledby="mobileLanguageDropdown">
-                                    <li><a class="dropdown-item lang-select-item active" href="#" data-lang="en">🇺🇸 English</a></li>
-                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="zh">🇨🇳 简体中文</a></li>
-                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="ja">🇯🇵 日本語</a></li>
-                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="ko">🇰🇷 한국어</a></li>
+                                     <li><a class="dropdown-item lang-select-item active" href="#" data-lang="en">us English</a></li>
+                                     <li><a class="dropdown-item lang-select-item" href="#" data-lang="zh">CN 简体中文</a></li>
+                                     <li><a class="dropdown-item lang-select-item" href="#" data-lang="ja">JP 日本語</a></li>
+                                     <li><a class="dropdown-item lang-select-item" href="#" data-lang="ko">KR 한국어</a></li>
+                                     <li><a class="dropdown-item lang-select-item" href="#" data-lang="pt">BR Português (Brasil)</a></li>
                                 </ul>
                             </div>
                             <button id="mobile-theme-toggle" class="mobile-menu-item" title="Toggle Dark Mode">
diff --git a/desktop-app/resources/js/script.js b/desktop-app/resources/js/script.js
index c25bbb9..49d7df9 100644
--- a/desktop-app/resources/js/script.js
+++ b/desktop-app/resources/js/script.js
@@ -3953,12 +3953,33 @@ This is a fully client-side application. Your content never leaves your browser
 
   let frPreferredDocked = false;
 
-  function toggleFrDockMode() {
+  function toggleFrDockMode(forceFloat = false) {
     const panel = document.getElementById('find-replace-modal');
     const dockBtn = document.getElementById('find-replace-dock');
     const contentCont = document.querySelector('.content-container');
     if (!panel || !dockBtn || !contentCont) return;
 
+    if (window.innerWidth <= 768 || forceFloat) {
+      isFrDocked = false;
+      panel.classList.remove('docked');
+      if (panel.parentElement !== document.body) {
+        document.body.appendChild(panel);
+      }
+      contentCont.classList.remove('fr-docked');
+      contentCont.style.setProperty('--dock-width', '0px');
+
+      panel.style.top = '';
+      panel.style.left = '';
+      panel.style.right = '';
+      
+      dockBtn.innerHTML = '<i class="bi bi-layout-sidebar-reverse"></i>';
+      dockBtn.title = "Toggle Dock Mode";
+      
+      panel.style.display = 'flex';
+      applyPaneWidths();
+      return;
+    }
+
     isFrDocked = !isFrDocked;
     
     // Save preference to localStorage
@@ -4119,7 +4140,12 @@ This is a fully client-side application. Your content never leaves your browser
     }
 
     // Restore docked/floating mode preference
-    const wasDockedPref = localStorage.getItem('find-replace-docked') === 'true';
+    let wasDockedPref = localStorage.getItem('find-replace-docked') === 'true';
+    
+    // Force floating-only mode on mobile/tablet viewports
+    if (window.innerWidth <= 768) {
+      wasDockedPref = false;
+    }
     
     if (wasDockedPref) {
       isFrDocked = false; // Set false so toggleFrDockMode() turns it to true
@@ -4456,6 +4482,28 @@ This is a fully client-side application. Your content never leaves your browser
     }
   }
 
+  function openHelpModal() {
+    if (helpModal) {
+      openAppModal(helpModal);
+    }
+  }
+
+  function openAboutModal() {
+    if (aboutModal) {
+      const aboutVersion = document.getElementById("about-version");
+      if (aboutVersion) {
+        aboutVersion.textContent = APP_VERSION;
+      }
+      openAppModal(aboutModal);
+    }
+  }
+
+  function openClearFormattingModal() {
+    if (clearFormattingModal) {
+      openAppModal(clearFormattingModal);
+    }
+  }
+
   function runMarkdownTool(action, button) {
     if (action === 'undo' || action === 'redo') {
       markdownEditor.focus();
@@ -4571,6 +4619,7 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function startResize(e) {
+    if (window.innerWidth <= 768) return;
     if (currentViewMode !== 'split') return;
     e.preventDefault();
     isResizing = true;
@@ -4579,6 +4628,7 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function startResizeTouch(e) {
+    if (window.innerWidth <= 768) return;
     if (currentViewMode !== 'split') return;
     e.preventDefault();
     isResizing = true;
@@ -4625,6 +4675,10 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function applyPaneWidths() {
+    if (window.innerWidth <= 768) {
+      resetPaneWidths();
+      return;
+    }
     if (currentViewMode !== 'split') return;
 
     const previewPercent = 100 - editorWidthPercent;
@@ -4733,7 +4787,12 @@ This is a fully client-side application. Your content never leaves your browser
 
   // Initialize resizer - Story 1.3
   initResizer();
-  window.addEventListener('resize', scheduleLineNumberUpdate);
+  window.addEventListener('resize', () => {
+    scheduleLineNumberUpdate();
+    if (window.innerWidth <= 768 && isFrDocked && isFindModalOpen) {
+      toggleFrDockMode(true);
+    }
+  });
 
   // View Mode Button Event Listeners - Story 1.1
   viewModeButtons.forEach(btn => {
@@ -6626,6 +6685,42 @@ This is a fully client-side application. Your content never leaves your browser
       insertTable: "표 삽입",
       findReplace: "찾기 및 바꾸기",
       placeholder: "여기에 마크다운 내용을 입력하세요..."
+    },
+    pt: {
+      title: "Visualizador de Markdown",
+      syncOff: "Desativar Sincronia",
+      syncOn: "Ativar Sincronia",
+      import: "Importar",
+      importFile: "De arquivos",
+      importGithub: "Do GitHub",
+      export: "Exportar",
+      exportMd: "Markdown (.md)",
+      exportHtml: "HTML",
+      exportPdf: "PDF",
+      copy: "Copiar",
+      copied: "Copiado!",
+      share: "Compartilhar",
+      reset: "Redefinir",
+      editor: "Editor",
+      split: "Dividido",
+      preview: "Visualizar",
+      minRead: "Min de leitura",
+      words: "Palavras",
+      chars: "Caracteres",
+      switchRtl: "Mudar para RTL",
+      switchLtr: "Mudar para LTR",
+      darkMode: "Modo Escuro",
+      lightMode: "Modo Claro",
+      helpTitle: "Ajuda do Visualizador de Markdown",
+      aboutTitle: "Sobre o Markdown",
+      shareTitle: "Compartilhar Documento",
+      renameTitle: "Renomear arquivo",
+      insertLink: "Inserir link",
+      insertRef: "Inserir referência",
+      insertImg: "Inserir imagem",
+      insertTable: "Inserir tabela",
+      findReplace: "Localizar & Substituir",
+      placeholder: "Digite seu markdown aqui..."
     }
   };
 
@@ -6643,12 +6738,12 @@ This is a fully client-side application. Your content never leaves your browser
     // Update dynamic current language labels in drop menus
     const labelEl = document.getElementById('current-lang-label');
     if (labelEl) {
-      const flags = { en: "🇺🇸 English", zh: "🇨🇳 简体中文", ja: "🇯🇵 日本語", ko: "🇰🇷 한국어" };
+      const flags = { en: "🇺🇸 English", zh: "🇨🇳 简体中文", ja: "🇯🇵 日本語", ko: "🇰🇷 한국어", pt: "🇧🇷 Português (Brasil)" };
       labelEl.textContent = flags[lang];
     }
     const mobileLabelEl = document.getElementById('mobile-current-lang-label');
     if (mobileLabelEl) {
-      const flags = { en: "🇺🇸 English", zh: "🇨🇳 简体中文", ja: "🇯🇵 日本語", ko: "🇰🇷 한국어" };
+      const flags = { en: "us English", zh: "CN 简体中文", ja: "JP 日本語", ko: "KR 한국어", pt: "BR Português (Brasil)" };
       mobileLabelEl.textContent = flags[lang];
     }
 
@@ -6821,6 +6916,7 @@ This is a fully client-side application. Your content never leaves your browser
       if (navLang.startsWith('zh')) lang = 'zh';
       else if (navLang.startsWith('ja')) lang = 'ja';
       else if (navLang.startsWith('ko')) lang = 'ko';
+      else if (navLang.startsWith('pt')) lang = 'pt';
     }
 
     if (!lang || !I18N_DICTS[lang]) {
diff --git a/desktop-app/resources/styles.css b/desktop-app/resources/styles.css
index e9fc5b3..ee4df05 100644
--- a/desktop-app/resources/styles.css
+++ b/desktop-app/resources/styles.css
@@ -3376,4 +3376,21 @@ html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang=
   flex: 1;
   position: relative;
   overflow: hidden;
+}
+
+/* ========================================
+   MOBILE FIND PANEL RESPONSIVE FIXES
+   ======================================== */
+@media (max-width: 768px) {
+  #find-replace-dock {
+    display: none !important;
+  }
+  
+  /* Prevent full screen expansion of floating panel on small mobile viewports */
+  .find-replace-panel {
+    width: calc(100% - 24px) !important;
+    right: 12px !important;
+    left: 12px !important;
+    top: 80px !important;
+  }
 }
\ No newline at end of file
diff --git a/index.html b/index.html
index 3658f04..73b66dc 100644
--- a/index.html
+++ b/index.html
@@ -18,6 +18,7 @@
     <link rel="alternate" hreflang="zh-Hans" href="https://markdownviewer.pages.dev/?lang=zh" />
     <link rel="alternate" hreflang="ja" href="https://markdownviewer.pages.dev/?lang=ja" />
     <link rel="alternate" hreflang="ko" href="https://markdownviewer.pages.dev/?lang=ko" />
+    <link rel="alternate" hreflang="pt-BR" href="https://markdownviewer.pages.dev/?lang=pt" />
 
     <!-- Asian Search Engine Verification Meta Tags -->
     <meta name="baidu-site-verification" content="baidu_verification_code_placeholder" />
@@ -187,6 +188,7 @@ <h1 class="h4 mb-0 me-2">Markdown Viewer</h1>
                             <li><a class="dropdown-item lang-select-item" href="#" data-lang="zh">🇨🇳 简体中文</a></li>
                             <li><a class="dropdown-item lang-select-item" href="#" data-lang="ja">🇯🇵 日本語</a></li>
                             <li><a class="dropdown-item lang-select-item" href="#" data-lang="ko">🇰🇷 한국어</a></li>
+                            <li><a class="dropdown-item lang-select-item" href="#" data-lang="pt">🇧🇷 Português (Brasil)</a></li>
                         </ul>
                     </div>
 
@@ -294,10 +296,11 @@ <h5>Menu</h5>
                                     <i class="bi bi-translate me-2"></i> Language: <span id="mobile-current-lang-label">English</span>
                                 </button>
                                 <ul class="dropdown-menu w-100" aria-labelledby="mobileLanguageDropdown">
-                                    <li><a class="dropdown-item lang-select-item active" href="#" data-lang="en">🇺🇸 English</a></li>
-                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="zh">🇨🇳 简体中文</a></li>
-                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="ja">🇯🇵 日本語</a></li>
-                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="ko">🇰🇷 한국어</a></li>
+                                    <li><a class="dropdown-item lang-select-item active" href="#" data-lang="en">us English</a></li>
+                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="zh">CN 简体中文</a></li>
+                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="ja">JP 日本語</a></li>
+                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="ko">KR 한국어</a></li>
+                                    <li><a class="dropdown-item lang-select-item" href="#" data-lang="pt">BR Português (Brasil)</a></li>
                                 </ul>
                             </div>
                             <button id="mobile-theme-toggle" class="mobile-menu-item" title="Toggle Dark Mode">
diff --git a/script.js b/script.js
index c25bbb9..49d7df9 100644
--- a/script.js
+++ b/script.js
@@ -3953,12 +3953,33 @@ This is a fully client-side application. Your content never leaves your browser
 
   let frPreferredDocked = false;
 
-  function toggleFrDockMode() {
+  function toggleFrDockMode(forceFloat = false) {
     const panel = document.getElementById('find-replace-modal');
     const dockBtn = document.getElementById('find-replace-dock');
     const contentCont = document.querySelector('.content-container');
     if (!panel || !dockBtn || !contentCont) return;
 
+    if (window.innerWidth <= 768 || forceFloat) {
+      isFrDocked = false;
+      panel.classList.remove('docked');
+      if (panel.parentElement !== document.body) {
+        document.body.appendChild(panel);
+      }
+      contentCont.classList.remove('fr-docked');
+      contentCont.style.setProperty('--dock-width', '0px');
+
+      panel.style.top = '';
+      panel.style.left = '';
+      panel.style.right = '';
+      
+      dockBtn.innerHTML = '<i class="bi bi-layout-sidebar-reverse"></i>';
+      dockBtn.title = "Toggle Dock Mode";
+      
+      panel.style.display = 'flex';
+      applyPaneWidths();
+      return;
+    }
+
     isFrDocked = !isFrDocked;
     
     // Save preference to localStorage
@@ -4119,7 +4140,12 @@ This is a fully client-side application. Your content never leaves your browser
     }
 
     // Restore docked/floating mode preference
-    const wasDockedPref = localStorage.getItem('find-replace-docked') === 'true';
+    let wasDockedPref = localStorage.getItem('find-replace-docked') === 'true';
+    
+    // Force floating-only mode on mobile/tablet viewports
+    if (window.innerWidth <= 768) {
+      wasDockedPref = false;
+    }
     
     if (wasDockedPref) {
       isFrDocked = false; // Set false so toggleFrDockMode() turns it to true
@@ -4456,6 +4482,28 @@ This is a fully client-side application. Your content never leaves your browser
     }
   }
 
+  function openHelpModal() {
+    if (helpModal) {
+      openAppModal(helpModal);
+    }
+  }
+
+  function openAboutModal() {
+    if (aboutModal) {
+      const aboutVersion = document.getElementById("about-version");
+      if (aboutVersion) {
+        aboutVersion.textContent = APP_VERSION;
+      }
+      openAppModal(aboutModal);
+    }
+  }
+
+  function openClearFormattingModal() {
+    if (clearFormattingModal) {
+      openAppModal(clearFormattingModal);
+    }
+  }
+
   function runMarkdownTool(action, button) {
     if (action === 'undo' || action === 'redo') {
       markdownEditor.focus();
@@ -4571,6 +4619,7 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function startResize(e) {
+    if (window.innerWidth <= 768) return;
     if (currentViewMode !== 'split') return;
     e.preventDefault();
     isResizing = true;
@@ -4579,6 +4628,7 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function startResizeTouch(e) {
+    if (window.innerWidth <= 768) return;
     if (currentViewMode !== 'split') return;
     e.preventDefault();
     isResizing = true;
@@ -4625,6 +4675,10 @@ This is a fully client-side application. Your content never leaves your browser
   }
 
   function applyPaneWidths() {
+    if (window.innerWidth <= 768) {
+      resetPaneWidths();
+      return;
+    }
     if (currentViewMode !== 'split') return;
 
     const previewPercent = 100 - editorWidthPercent;
@@ -4733,7 +4787,12 @@ This is a fully client-side application. Your content never leaves your browser
 
   // Initialize resizer - Story 1.3
   initResizer();
-  window.addEventListener('resize', scheduleLineNumberUpdate);
+  window.addEventListener('resize', () => {
+    scheduleLineNumberUpdate();
+    if (window.innerWidth <= 768 && isFrDocked && isFindModalOpen) {
+      toggleFrDockMode(true);
+    }
+  });
 
   // View Mode Button Event Listeners - Story 1.1
   viewModeButtons.forEach(btn => {
@@ -6626,6 +6685,42 @@ This is a fully client-side application. Your content never leaves your browser
       insertTable: "표 삽입",
       findReplace: "찾기 및 바꾸기",
       placeholder: "여기에 마크다운 내용을 입력하세요..."
+    },
+    pt: {
+      title: "Visualizador de Markdown",
+      syncOff: "Desativar Sincronia",
+      syncOn: "Ativar Sincronia",
+      import: "Importar",
+      importFile: "De arquivos",
+      importGithub: "Do GitHub",
+      export: "Exportar",
+      exportMd: "Markdown (.md)",
+      exportHtml: "HTML",
+      exportPdf: "PDF",
+      copy: "Copiar",
+      copied: "Copiado!",
+      share: "Compartilhar",
+      reset: "Redefinir",
+      editor: "Editor",
+      split: "Dividido",
+      preview: "Visualizar",
+      minRead: "Min de leitura",
+      words: "Palavras",
+      chars: "Caracteres",
+      switchRtl: "Mudar para RTL",
+      switchLtr: "Mudar para LTR",
+      darkMode: "Modo Escuro",
+      lightMode: "Modo Claro",
+      helpTitle: "Ajuda do Visualizador de Markdown",
+      aboutTitle: "Sobre o Markdown",
+      shareTitle: "Compartilhar Documento",
+      renameTitle: "Renomear arquivo",
+      insertLink: "Inserir link",
+      insertRef: "Inserir referência",
+      insertImg: "Inserir imagem",
+      insertTable: "Inserir tabela",
+      findReplace: "Localizar & Substituir",
+      placeholder: "Digite seu markdown aqui..."
     }
   };
 
@@ -6643,12 +6738,12 @@ This is a fully client-side application. Your content never leaves your browser
     // Update dynamic current language labels in drop menus
     const labelEl = document.getElementById('current-lang-label');
     if (labelEl) {
-      const flags = { en: "🇺🇸 English", zh: "🇨🇳 简体中文", ja: "🇯🇵 日本語", ko: "🇰🇷 한국어" };
+      const flags = { en: "🇺🇸 English", zh: "🇨🇳 简体中文", ja: "🇯🇵 日本語", ko: "🇰🇷 한국어", pt: "🇧🇷 Português (Brasil)" };
       labelEl.textContent = flags[lang];
     }
     const mobileLabelEl = document.getElementById('mobile-current-lang-label');
     if (mobileLabelEl) {
-      const flags = { en: "🇺🇸 English", zh: "🇨🇳 简体中文", ja: "🇯🇵 日本語", ko: "🇰🇷 한국어" };
+      const flags = { en: "us English", zh: "CN 简体中文", ja: "JP 日本語", ko: "KR 한국어", pt: "BR Português (Brasil)" };
       mobileLabelEl.textContent = flags[lang];
     }
 
@@ -6821,6 +6916,7 @@ This is a fully client-side application. Your content never leaves your browser
       if (navLang.startsWith('zh')) lang = 'zh';
       else if (navLang.startsWith('ja')) lang = 'ja';
       else if (navLang.startsWith('ko')) lang = 'ko';
+      else if (navLang.startsWith('pt')) lang = 'pt';
     }
 
     if (!lang || !I18N_DICTS[lang]) {
diff --git a/styles.css b/styles.css
index e9fc5b3..ee4df05 100644
--- a/styles.css
+++ b/styles.css
@@ -3376,4 +3376,21 @@ html[lang="ko"] .markdown-body h1, html[lang="ko"] .markdown-body h2, html[lang=
   flex: 1;
   position: relative;
   overflow: hidden;
+}
+
+/* ========================================
+   MOBILE FIND PANEL RESPONSIVE FIXES
+   ======================================== */
+@media (max-width: 768px) {
+  #find-replace-dock {
+    display: none !important;
+  }
+  
+  /* Prevent full screen expansion of floating panel on small mobile viewports */
+  .find-replace-panel {
+    width: calc(100% - 24px) !important;
+    right: 12px !important;
+    left: 12px !important;
+    top: 80px !important;
+  }
 }
\ No newline at end of file
diff --git a/sw.js b/sw.js
index 74a04a0..a4aa74a 100644
--- a/sw.js
+++ b/sw.js
@@ -1,4 +1,4 @@
-const CACHE_NAME = 'markdown-viewer-cache-v3.6.3';
+const CACHE_NAME = 'markdown-viewer-cache-v3.6.4';
 const ASSETS = [
   './',
   './index.html',