feat: improve mobile responsiveness

- Add mobile navigation drawer with hamburger menu
- Sidebar slides in as overlay on mobile (<768px)
- Close button inside sidebar for mobile
- Ensure touch targets are at least 44px on mobile
- Make modals full-screen on mobile
- Editor toolbar scrolls horizontally on mobile
- Improve spacing and typography for small screens
- Keep dark theme consistent across breakpoints
- Projects page cards stack vertically on mobile
- Document cards full-width on mobile

public/css/style.css

@@ -1239,10 +1239,90 @@ ul, ol {
   to { transform: rotate(360deg); }
 }
 
+/* === Mobile Navigation Drawer === */
+.mobile-nav-btn {
+  display: none;
+  width: 44px;
+  height: 44px;
+  align-items: center;
+  justify-content: center;
+  border-radius: var(--radius-md);
+  color: var(--color-text-secondary);
+  font-size: 1.25rem;
+  transition: var(--transition-fast);
+  flex-shrink: 0;
+}
+
+.mobile-nav-btn:hover {
+  background: var(--color-hover);
+  color: var(--color-text);
+}
+
+.sidebar-overlay {
+  display: none;
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.5);
+  z-index: calc(var(--z-sidebar) - 1);
+  opacity: 0;
+  transition: opacity 0.2s ease;
+}
+
+.sidebar-overlay.active {
+  opacity: 1;
+}
+
+.sidebar-close-btn {
+  display: none;
+  position: absolute;
+  top: var(--space-3);
+  right: var(--space-3);
+  width: 44px;
+  height: 44px;
+  align-items: center;
+  justify-content: center;
+  border-radius: var(--radius-md);
+  color: var(--color-text-secondary);
+  font-size: 1.25rem;
+  z-index: 1;
+}
+
+.sidebar-close-btn:hover {
+  background: var(--color-hover);
+  color: var(--color-text);
+}
+
 /* === Responsive === */
 @media (max-width: 1024px) {
   .sidebar {
-    display: none;
+    position: fixed;
+    left: 0;
+    top: 0;
+    bottom: 0;
+    z-index: var(--z-sidebar);
+    transform: translateX(-100%);
+    transition: transform 0.25s ease;
+    box-shadow: var(--shadow-lg);
+  }
+
+  .sidebar.mobile-open {
+    transform: translateX(0);
+  }
+
+  .sidebar-scroll {
+    padding-top: 56px;
+  }
+
+  .sidebar-close-btn {
+    display: flex;
+  }
+
+  .mobile-nav-btn {
+    display: flex;
+  }
+
+  .sidebar-overlay {
+    display: block;
   }
 
   .doc-sidebar {
@@ -1276,22 +1356,300 @@ ul, ol {
   }
 
   .content-body {
-    padding: var(--space-4);
+    padding: var(--space-3);
   }
 
   .doc-grid {
     grid-template-columns: 1fr;
+    gap: var(--space-3);
+  }
+
+  .doc-card {
+    padding: var(--space-4);
+    min-height: 44px;
+  }
+
+  .doc-card-actions {
+    opacity: 1;
+    position: static;
+    margin-top: var(--space-2);
+    display: flex;
+    gap: var(--space-2);
   }
 
   .modal {
     min-width: auto;
-    margin: var(--space-4);
+    width: 100%;
+    height: 100%;
+    max-width: 100%;
+    margin: 0;
+    border-radius: 0;
+    display: flex;
+    flex-direction: column;
+  }
+
+  .modal-backdrop {
+    padding: 0;
+    align-items: stretch;
+  }
+
+  .modal-header {
+    padding: var(--space-4);
+    flex-shrink: 0;
+  }
+
+  .modal-body {
+    flex: 1;
+    overflow-y: auto;
+    padding: var(--space-4);
+  }
+
+  .modal-footer {
+    flex-shrink: 0;
+    padding: var(--space-4);
+    gap: var(--space-3);
   }
 
   .login-card {
     margin: var(--space-4);
     padding: var(--space-6);
   }
+
+  /* === Projects Page Mobile === */
+  .projects-page {
+    padding: var(--space-4);
+  }
+
+  .projects-header {
+    margin-bottom: var(--space-6);
+  }
+
+  .projects-header h1 {
+    font-size: 1.5rem;
+  }
+
+  .projects-grid {
+    grid-template-columns: 1fr;
+    gap: var(--space-3);
+  }
+
+  .project-card {
+    padding: var(--space-4);
+  }
+
+  .project-card-header {
+    flex-direction: column;
+    gap: var(--space-3);
+  }
+
+  .project-icon {
+    font-size: 1.5rem;
+  }
+
+  .project-name {
+    font-size: 1rem;
+  }
+
+  /* === Header Mobile === */
+  .app-header {
+    padding: var(--space-2) var(--space-3);
+    gap: var(--space-2);
+  }
+
+  .app-header .logo {
+    font-size: 1rem;
+    flex: 1;
+    min-width: 0;
+  }
+
+  .header-actions .btn {
+    padding: var(--space-2) var(--space-3);
+    font-size: 0.8125rem;
+  }
+
+  /* === Content Header Mobile === */
+  .content-header {
+    padding: var(--space-3) var(--space-4);
+    flex-wrap: wrap;
+    gap: var(--space-3);
+  }
+
+  .content-header-left {
+    flex-direction: column;
+    gap: var(--space-1);
+    align-items: flex-start;
+  }
+
+  .content-header-left h1 {
+    font-size: 1.125rem;
+  }
+
+  .content-header-right {
+    width: 100%;
+    flex-wrap: wrap;
+  }
+
+  .search-box-inline {
+    flex: 1;
+    min-width: 0;
+  }
+
+  .search-box-inline input {
+    width: 100%;
+  }
+
+  /* === Editor Mobile === */
+  .editor-container {
+    max-width: 100%;
+  }
+
+  .editor-header {
+    padding: var(--space-3) var(--space-4);
+  }
+
+  .editor-form {
+    padding: var(--space-4);
+  }
+
+  .form-row {
+    grid-template-columns: 1fr;
+    gap: var(--space-3);
+  }
+
+  .editor-toolbar {
+    overflow-x: auto;
+    -webkit-overflow-scrolling: touch;
+    gap: var(--space-1);
+    padding: var(--space-2);
+    flex-wrap: nowrap;
+    justify-content: flex-start;
+  }
+
+  .toolbar-btn {
+    width: 44px;
+    height: 44px;
+    flex-shrink: 0;
+  }
+
+  .toolbar-separator {
+    flex-shrink: 0;
+  }
+
+  .toolbar-tabs {
+    margin-left: auto;
+    flex-shrink: 0;
+  }
+
+  .tab-btn {
+    padding: var(--space-2) var(--space-3);
+    min-height: 44px;
+    display: flex;
+    align-items: center;
+  }
+
+  .form-group textarea {
+    min-height: 200px;
+    font-size: 16px; /* Prevents zoom on iOS */
+  }
+
+  .form-group input,
+  .form-group select {
+    min-height: 44px;
+    font-size: 16px; /* Prevents zoom on iOS */
+  }
+
+  /* === Doc Card Mobile === */
+  .doc-card-header {
+    flex-wrap: wrap;
+  }
+
+  .doc-title {
+    font-size: 0.9375rem;
+  }
+
+  .doc-tags {
+    margin-top: var(--space-2);
+  }
+
+  .doc-meta {
+    flex-wrap: wrap;
+    gap: var(--space-2);
+  }
+
+  /* === Touch Targets === */
+  .btn {
+    min-height: 44px;
+    min-width: 44px;
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+  }
+
+  .btn-icon-only {
+    width: 44px;
+    height: 44px;
+  }
+
+  .tree-item {
+    min-height: 44px;
+    padding: var(--space-2) var(--space-3);
+  }
+
+  .tree-item .tree-action {
+    width: 32px;
+    height: 32px;
+    opacity: 1;
+  }
+
+  .tag-item {
+    min-height: 44px;
+    padding: var(--space-2) var(--space-3);
+  }
+
+  .quick-link {
+    min-height: 44px;
+    padding: var(--space-2) var(--space-3);
+  }
+
+  .doc-card {
+    cursor: pointer;
+  }
+
+  /* === Empty State Mobile === */
+  .empty-state {
+    padding: var(--space-8);
+  }
+
+  /* === Breadcrumbs Mobile === */
+  .breadcrumb-nav {
+    margin-left: 0;
+    flex-wrap: wrap;
+    font-size: 0.8125rem;
+  }
+
+  /* === Toast Mobile === */
+  #toast-container {
+    bottom: var(--space-4);
+    right: var(--space-4);
+    left: var(--space-4);
+  }
+
+  .toast {
+    min-width: auto;
+    width: 100%;
+  }
+}
+
+/* Ensure minimum touch target size */
+@media (max-width: 768px) {
+  a, button, [role="button"] {
+    min-height: 44px;
+    min-width: 44px;
+  }
+
+  input, select, textarea {
+    font-size: 16px; /* Prevents iOS zoom */
+  }
 }
 
 /* === Projects Page === */

public/js/components/sidebar.js

@@ -25,70 +25,36 @@ export function renderSidebar({ libraries, tags, selectedLibrary, selectedTag, o
       .join('');
   };
 
-  // Store callbacks in a way that's safe and doesn't rely on inline script execution
-  const callbacks = {
-    onSelectLibrary,
-    onSelectTag,
-    onHome
-  };
-
   return `
-    <aside class="sidebar">
+    <div class="sidebar-scroll">
-      <div class="sidebar-scroll">
+      <div class="sidebar-section">
-        <div class="sidebar-section">
+        <h3>📚 Libraries</h3>
-          <h3>📚 Libraries</h3>
+        <div class="library-tree">
-          <div class="library-tree">
+          <div class="tree-item ${!selectedLibrary ? 'active' : ''}" data-action="home">
-            <div class="tree-item ${!selectedLibrary ? 'active' : ''}" data-action="home">
+            <span class="icon">🏠</span>
-              <span class="icon">🏠</span>
+            <span class="label">All Documents</span>
-              <span class="label">All Documents</span>
-            </div>
-            ${buildLibraryTree(libraries)}
           </div>
-        </div>
+          ${buildLibraryTree(libraries)}
-        <div class="sidebar-section">
-          <h3>🏷️ Tags</h3>
-          <div class="tag-list">
-            ${tags.map(tag => `
-              <div class="tag-item ${selectedTag === tag.name ? 'active' : ''}" data-action="tag" data-tag="${escapeHtml(tag.name)}">
-                <span>#${escapeHtml(tag.name)}</span>
-                <span class="tag-count">${tag.count}</span>
-              </div>
-            `).join('')}
-          </div>
-        </div>
-        <div class="quick-links">
-          <a class="quick-link" data-action="home">📋 All Documents</a>
-          <a class="quick-link" href="#" onclick="window.app.navigate('projects'); return false;">📂 Projects</a>
-          <a class="quick-link" href="#" onclick="window.showNewDocModal(); return false;">📄 New Document</a>
-          <a class="quick-link" href="#" onclick="window.showNewLibraryModal(); return false;">📁 New Library</a>
         </div>
       </div>
-    </aside>
+      <div class="sidebar-section">
-    <script>
+        <h3>🏷️ Tags</h3>
-      (function() {
+        <div class="tag-list">
-        var callbacks = window.__sidebarCallbacks;
+          ${tags.map(tag => `
-        document.querySelectorAll('[data-action="home"]').forEach(function(el) {
+            <div class="tag-item ${selectedTag === tag.name ? 'active' : ''}" data-action="tag" data-tag="${escapeHtml(tag.name)}">
-          el.addEventListener('click', function(e) {
+              <span>#${escapeHtml(tag.name)}</span>
-            e.stopPropagation();
+              <span class="tag-count">${tag.count}</span>
-            if (callbacks && callbacks.onHome) callbacks.onHome();
+            </div>
-          });
+          `).join('')}
-        });
+        </div>
-        document.querySelectorAll('[data-action="library"]').forEach(function(el) {
+      </div>
-          el.addEventListener('click', function(e) {
+      <div class="quick-links">
-            e.stopPropagation();
+        <a class="quick-link" data-action="home">📋 All Documents</a>
-            var id = this.getAttribute('data-library-id');
+        <a class="quick-link" href="#" onclick="window.app.navigate('projects'); return false;">📂 Projects</a>
-            if (callbacks && callbacks.onSelectLibrary) callbacks.onSelectLibrary(id);
+        <a class="quick-link" href="#" onclick="window.showNewDocModal(); return false;">📄 New Document</a>
-          });
+        <a class="quick-link" href="#" onclick="window.showNewLibraryModal(); return false;">📁 New Library</a>
-        });
+      </div>
-        document.querySelectorAll('[data-action="tag"]').forEach(function(el) {
+    </div>
-          el.addEventListener('click', function(e) {
-            e.stopPropagation();
-            var tag = this.getAttribute('data-tag');
-            if (callbacks && callbacks.onSelectTag) callbacks.onSelectTag(tag);
-          });
-        });
-      })();
-    </script>
   `;
 }
 

public/js/views/dashboard.js

@@ -77,29 +77,33 @@ export async function renderDashboard(app) {
 
     appEl.innerHTML = `
       <header class="app-header">
+        <button class="mobile-nav-btn" onclick="toggleMobileSidebar()" title="Menu">☰</button>
         <div class="logo">📝 SimpleNote</div>
         <div class="search-box">
           <span class="icon">🔍</span>
           <input type="text" id="search-input" placeholder="Search documents..." value="${searchQuery}">
         </div>
         <div class="header-actions">
-          <button class="btn btn-primary" onclick="window.showNewDocModal()">+ New Document</button>
+          <button class="btn btn-primary" onclick="window.showNewDocModal()">+ New</button>
-          <button class="btn btn-ghost" onclick="window.showNewLibraryModal()">📁 New Library</button>
         </div>
       </header>
+      <div class="sidebar-overlay" onclick="closeMobileSidebar()"></div>
       <div class="app-layout">
-        ${renderSidebar({
+        <aside class="sidebar" id="sidebar">
-          libraries,
+          <button class="sidebar-close-btn" onclick="closeMobileSidebar()">✕</button>
-          tags,
+          ${renderSidebar({
-          selectedLibrary,
+            libraries,
-          selectedTag,
+            tags,
-          ...sidebarCallbacks
+            selectedLibrary,
-        })}
+            selectedTag,
+            ...sidebarCallbacks
+          })}
+        </aside>
         <main class="main-content">
           <div class="content-header">
             <h1>${selectedLibrary ? getLibraryName(libraries, selectedLibrary) : selectedTag ? `#${selectedTag}` : 'All Documents'}</h1>
             <div class="header-actions">
-              <button class="btn btn-primary" onclick="window.showNewDocModal()">+ New Document</button>
+              <button class="btn btn-primary" onclick="window.showNewDocModal()">+ New</button>
             </div>
           </div>
           <div class="content-body">
@@ -120,12 +124,54 @@ export async function renderDashboard(app) {
       </div>
     `;
 
+    // Mobile sidebar functions
+    window.toggleMobileSidebar = function() {
+      const sidebar = document.getElementById('sidebar');
+      const overlay = document.querySelector('.sidebar-overlay');
+      if (sidebar) {
+        sidebar.classList.toggle('mobile-open');
+        if (overlay) overlay.classList.toggle('active');
+      }
+    };
+
+    window.closeMobileSidebar = function() {
+      const sidebar = document.getElementById('sidebar');
+      const overlay = document.querySelector('.sidebar-overlay');
+      if (sidebar) {
+        sidebar.classList.remove('mobile-open');
+        if (overlay) overlay.classList.remove('active');
+      }
+    };
+
     // Event listeners
     const searchInput = document.getElementById('search-input');
     searchInput.oninput = (e) => {
       searchQuery = e.target.value;
       render();
     };
+
+    // Sidebar item listeners
+    document.querySelectorAll('[data-action="home"]').forEach(el => {
+      el.addEventListener('click', (e) => {
+        e.stopPropagation();
+        sidebarCallbacks.onHome();
+        closeMobileSidebar();
+      });
+    });
+    document.querySelectorAll('[data-action="library"]').forEach(el => {
+      el.addEventListener('click', (e) => {
+        e.stopPropagation();
+        sidebarCallbacks.onSelectLibrary(el.getAttribute('data-library-id'));
+        closeMobileSidebar();
+      });
+    });
+    document.querySelectorAll('[data-action="tag"]').forEach(el => {
+      el.addEventListener('click', (e) => {
+        e.stopPropagation();
+        sidebarCallbacks.onSelectTag(el.getAttribute('data-tag'));
+        closeMobileSidebar();
+      });
+    });
   }
 
   render();

public/js/views/projectView.js

@@ -74,6 +74,7 @@ export async function renderProjectView(app) {
 
     appEl.innerHTML = `
       <header class="app-header">
+        <button class="mobile-nav-btn" onclick="toggleMobileSidebar()" title="Menu">☰</button>
         <div class="logo">📝 SimpleNote</div>
         <div class="breadcrumb-nav">
           <span class="breadcrumb-link" onclick="window.app.navigate('projects')">Projects</span>
@@ -85,8 +86,10 @@ export async function renderProjectView(app) {
           <button class="btn btn-ghost" onclick="window.confirmDeleteProject('${project.id}')" title="Delete Project">🗑️</button>
         </div>
       </header>
+      <div class="sidebar-overlay" onclick="closeMobileSidebar()"></div>
       <div class="app-layout">
-        <aside class="sidebar project-sidebar">
+        <aside class="sidebar project-sidebar" id="sidebar">
+          <button class="sidebar-close-btn" onclick="closeMobileSidebar()">✕</button>
           <div class="sidebar-scroll">
             <div class="sidebar-section">
               <div class="section-header">
@@ -130,7 +133,7 @@ export async function renderProjectView(app) {
                 <span class="icon">🔍</span>
                 <input type="text" id="search-input" placeholder="Search documents..." value="${escapeHtml(searchQuery)}">
               </div>
-              <button class="btn btn-primary" onclick="window.showNewDocModal('${projectId}', '${selectedFolderId || ''}')">+ New Document</button>
+              <button class="btn btn-primary" onclick="window.showNewDocModal('${projectId}', '${selectedFolderId || ''}')">+ New</button>
             </div>
           </div>
           <div class="content-body">
@@ -155,6 +158,25 @@ export async function renderProjectView(app) {
     attachEventListeners();
   }
 
+  // Mobile sidebar functions
+  window.toggleMobileSidebar = function() {
+    const sidebar = document.getElementById('sidebar');
+    const overlay = document.querySelector('.sidebar-overlay');
+    if (sidebar) {
+      sidebar.classList.toggle('mobile-open');
+      if (overlay) overlay.classList.toggle('active');
+    }
+  };
+
+  window.closeMobileSidebar = function() {
+    const sidebar = document.getElementById('sidebar');
+    const overlay = document.querySelector('.sidebar-overlay');
+    if (sidebar) {
+      sidebar.classList.remove('mobile-open');
+      if (overlay) overlay.classList.remove('active');
+    }
+  };
+
   function attachEventListeners() {
     // Search
     const searchInput = document.getElementById('search-input');

public/js/views/projects.js

@@ -19,7 +19,7 @@ export async function renderProjects(app) {
       <header class="app-header">
         <div class="logo">📝 SimpleNote</div>
         <div class="header-actions">
-          <button class="btn btn-primary" onclick="window.showNewProjectModal()">+ New Project</button>
+          <button class="btn btn-primary" onclick="window.showNewProjectModal()">+ New</button>
         </div>
       </header>
       <div class="projects-page">