diff --git a/src/app/globals.css b/src/app/globals.css
index 8b6441d..cd8cbd1 100644
--- a/src/app/globals.css
+++ b/src/app/globals.css
@@ -1,27 +1,27 @@
 @import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&display=swap');
 
-:root {
+:root, [data-theme="dark"] {
   --bg-primary: #0a0a0f;
   --bg-secondary: #12121a;
   --bg-card: #1a1a2e;
   --bg-card-hover: #22223a;
   --bg-elevated: #252540;
-  --border-color: rgba(255,255,255,0.06);
+  --border-color: rgba(255,255,255,0.09);
   --border-active: rgba(108,99,255,0.5);
-  --text-primary: #f0f0f5;
-  --text-secondary: #8888a0;
-  --text-muted: #55556a;
+  --text-primary: #f8fafc;
+  --text-secondary: #cbd5e1;
+  --text-muted: #94a3b8;
   --accent: #6C63FF;
   --accent-hover: #5a52e0;
   --accent-glow: rgba(108,99,255,0.25);
   --success: #22c55e;
-  --success-bg: rgba(34,197,94,0.1);
+  --success-bg: rgba(34,197,94,0.12);
   --warning: #f59e0b;
-  --warning-bg: rgba(245,158,11,0.1);
+  --warning-bg: rgba(245,158,11,0.12);
   --danger: #ef4444;
-  --danger-bg: rgba(239,68,68,0.1);
+  --danger-bg: rgba(239,68,68,0.12);
   --info: #3b82f6;
-  --info-bg: rgba(59,130,246,0.1);
+  --info-bg: rgba(59,130,246,0.12);
   --gradient-primary: linear-gradient(135deg, #6C63FF 0%, #a855f7 100%);
   --gradient-card: linear-gradient(145deg, rgba(26,26,46,0.8), rgba(18,18,26,0.9));
   --shadow-sm: 0 2px 8px rgba(0,0,0,0.3);
@@ -34,6 +34,36 @@
   --radius-xl: 24px;
 }
 
+[data-theme="light"] {
+  --bg-primary: #f8fafc;
+  --bg-secondary: #ffffff;
+  --bg-card: #ffffff;
+  --bg-card-hover: #f1f5f9;
+  --bg-elevated: #f1f5f9;
+  --border-color: #e2e8f0;
+  --border-active: #6C63FF;
+  --text-primary: #0f172a;
+  --text-secondary: #475569;
+  --text-muted: #64748b;
+  --accent: #6C63FF;
+  --accent-hover: #5a52e0;
+  --accent-glow: rgba(108,99,255,0.12);
+  --success: #16a34a;
+  --success-bg: rgba(22,163,74,0.1);
+  --warning: #d97706;
+  --warning-bg: rgba(217,119,6,0.1);
+  --danger: #dc2626;
+  --danger-bg: rgba(220,38,38,0.1);
+  --info: #2563eb;
+  --info-bg: rgba(37,99,235,0.1);
+  --gradient-primary: linear-gradient(135deg, #6C63FF 0%, #8b5cf6 100%);
+  --gradient-card: linear-gradient(145deg, #ffffff, #f8fafc);
+  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
+  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
+  --shadow-lg: 0 10px 25px rgba(0,0,0,0.1);
+  --shadow-glow: 0 0 20px rgba(108,99,255,0.1);
+}
+
 * { margin: 0; padding: 0; box-sizing: border-box; }
 
 html, body { height: 100%; }
@@ -1016,3 +1046,119 @@ tr:hover td { background: var(--bg-card-hover); }
   font-weight: 600;
   box-shadow: 0 2px 10px rgba(108, 99, 255, 0.4);
 }
+
+/* === RESPONSIVE BREAKPOINTS (PC, TABLET, MOBILE) === */
+
+/* Desktop & Laptop (> 1024px) */
+@media (min-width: 1025px) {
+  .mobile-close-btn { display: none !important; }
+}
+
+/* Tablet (769px - 1024px) */
+@media (max-width: 1024px) and (min-width: 769px) {
+  .main-content { margin-left: 240px; }
+  .main-content.collapsed { margin-left: 76px; }
+  .stats-grid { grid-template-columns: repeat(2, 1fr); }
+  .page-content { padding: 24px; }
+  .topbar { padding: 16px 24px; }
+}
+
+/* Mobile (<= 768px) */
+@media (max-width: 768px) {
+  .sidebar {
+    position: fixed;
+    top: 0;
+    left: 0;
+    bottom: 0;
+    width: 280px !important;
+    z-index: 1000;
+    transform: translateX(-100%);
+    transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1);
+    box-shadow: 0 0 40px rgba(0,0,0,0.5);
+  }
+
+  .sidebar.open {
+    transform: translateX(0);
+  }
+
+  .desktop-collapse-btn { display: none !important; }
+  .mobile-close-btn { display: flex !important; }
+
+  .main-content, .main-content.collapsed {
+    margin-left: 0 !important;
+    width: 100% !important;
+  }
+
+  .topbar {
+    padding: 14px 16px;
+  }
+
+  .topbar-left h1 {
+    font-size: 18px;
+  }
+
+  .search-box {
+    display: none;
+  }
+
+  .page-content {
+    padding: 16px;
+  }
+
+  .stats-grid {
+    grid-template-columns: 1fr;
+  }
+
+  .grid-2, .grid-3 {
+    grid-template-columns: 1fr;
+  }
+
+  .view-mode-selector {
+    width: 100%;
+    justify-content: space-between;
+  }
+
+  .view-mode-btn {
+    flex: 1;
+    justify-content: center;
+    padding: 8px 6px;
+    font-size: 12px;
+  }
+}
+
+/* === LIGHT THEME OVERRIDES === */
+[data-theme="light"] .sidebar {
+  background: #ffffff;
+  border-right: 1px solid #e2e8f0;
+}
+
+[data-theme="light"] .topbar {
+  background: rgba(255, 255, 255, 0.9);
+  border-bottom: 1px solid #e2e8f0;
+}
+
+[data-theme="light"] .nav-item {
+  color: #475569;
+}
+
+[data-theme="light"] .nav-item:hover {
+  background: #f1f5f9;
+  color: #0f172a;
+}
+
+[data-theme="light"] .nav-item.active {
+  background: rgba(108, 99, 255, 0.12);
+  color: #6C63FF;
+}
+
+[data-theme="light"] .card {
+  background: #ffffff;
+  border-color: #e2e8f0;
+  box-shadow: 0 1px 4px rgba(0,0,0,0.05);
+}
+
+[data-theme="light"] .form-input, [data-theme="light"] .form-select {
+  background: #f8fafc;
+  border-color: #cbd5e1;
+  color: #0f172a;
+}
diff --git a/src/components/Topbar.tsx b/src/components/Topbar.tsx
index fc64df7..8828797 100644
--- a/src/components/Topbar.tsx
+++ b/src/components/Topbar.tsx
@@ -1,5 +1,5 @@
 import { useState, useEffect, useRef } from 'react';
-import { Bell, Menu, Search, LogOut, User, CheckCircle, AlertCircle } from 'lucide-react';
+import { Bell, Menu, Search, LogOut, User, CheckCircle, AlertCircle, Sun, Moon } from 'lucide-react';
 
 interface TopbarProps {
   title: string;
@@ -18,6 +18,7 @@ export default function Topbar({ title, subtitle, onMenuClick, onNavigate }: Top
   const [avatarInitials, setAvatarInitials] = useState('AD');
   const [tenantName, setTenantName] = useState('Administrador');
   const [email, setEmail] = useState('admin@agendapro.com');
+  const [theme, setTheme] = useState<'dark' | 'light'>('dark');
   
   const [showNotifications, setShowNotifications] = useState(false);
   const [showProfile, setShowProfile] = useState(false);
@@ -26,6 +27,19 @@ export default function Topbar({ title, subtitle, onMenuClick, onNavigate }: Top
   const notifRef = useRef<HTMLDivElement>(null);
   const profileRef = useRef<HTMLDivElement>(null);
 
+  useEffect(() => {
+    const savedTheme = (localStorage.getItem('agendapro_theme') as 'dark' | 'light') || 'dark';
+    setTheme(savedTheme);
+    document.documentElement.setAttribute('data-theme', savedTheme);
+  }, []);
+
+  const toggleTheme = () => {
+    const nextTheme = theme === 'dark' ? 'light' : 'dark';
+    setTheme(nextTheme);
+    document.documentElement.setAttribute('data-theme', nextTheme);
+    localStorage.setItem('agendapro_theme', nextTheme);
+  };
+
   const fetchNotifications = async () => {
     const slug = localStorage.getItem('agendapro_tenant_slug') || 'barbearia-premium';
     try {
@@ -157,6 +171,16 @@ export default function Topbar({ title, subtitle, onMenuClick, onNavigate }: Top
           <Search size={16} />
           <input className="form-input" placeholder="Buscar..." style={{ width: '240px', paddingLeft: '36px' }} />
         </div>
+
+        <button 
+          type="button" 
+          className="btn-ghost btn-icon" 
+          onClick={toggleTheme} 
+          title={theme === 'dark' ? "Mudar para Modo Claro" : "Mudar para Modo Escuro"}
+          style={{ borderRadius: '50%' }}
+        >
+          {theme === 'dark' ? <Sun size={20} style={{ color: '#f59e0b' }} /> : <Moon size={20} style={{ color: '#6C63FF' }} />}
+        </button>
         
         <div style={{ position: 'relative' }} ref={notifRef}>
           <button className="btn-ghost btn-icon" style={{ position: 'relative' }} onClick={handleNotificationClick}>