diff --git a/includes/style.php b/includes/style.php
index ddee068..3aad426 100644
--- a/includes/style.php
+++ b/includes/style.php
@@ -13,6 +13,20 @@
   --yellow:  #d29922;
 }
 
+[data-theme="light"] {
+  --bg:      #ffffff;
+  --surface: #f6f8fa;
+  --border:  #d0d7de;
+  --text:    #1f2328;
+  --muted:   #656d76;
+  --accent:  #0969da;
+  --green:   #1a7f37;
+  --red:     #cf222e;
+  --yellow:  #9a6700;
+}
+
+*, *::before, *::after { transition: background-color .2s, border-color .2s, color .2s; }
+
 body { background: var(--bg); color: var(--text); font: 14px/1.6 'Segoe UI', system-ui, sans-serif; }
 
 header {
@@ -64,7 +78,7 @@ label input[type=text], label input[type=url], label input[type=password], label
 label input:focus { outline: none; border-color: var(--accent); }
 
 button[type=submit], .btn {
-  background: var(--accent); color: #0d1117; border: none; border-radius: 5px;
+  background: var(--accent); color: #fff; border: none; border-radius: 5px;
   padding: .5rem 1.1rem; font-size: .9rem; font-weight: 600; cursor: pointer;
 }
 button[type=submit]:hover { opacity: .85; }
@@ -95,3 +109,10 @@ footer {
   border-top: 1px solid var(--border);
 }
 footer span { color: var(--accent); }
+
+.theme-toggle {
+  background: none; border: 1px solid var(--border); border-radius: 5px;
+  color: var(--muted); cursor: pointer; font-size: .8rem;
+  padding: .2rem .55rem; line-height: 1.6;
+}
+.theme-toggle:hover { color: var(--accent); border-color: var(--accent); }
diff --git a/includes/theme_toggle.php b/includes/theme_toggle.php
new file mode 100644
index 0000000..9fc59a5
--- /dev/null
+++ b/includes/theme_toggle.php
@@ -0,0 +1,16 @@
+<button class="theme-toggle" id="theme-toggle" title="Toggle theme" onclick="
+  var next = document.documentElement.getAttribute('data-theme') === 'light' ? 'dark' : 'light';
+  document.documentElement.setAttribute('data-theme', next);
+  localStorage.setItem('theme', next);
+  this.textContent = next === 'dark' ? '☀' : '☾';
+">☀</button>
+<script>
+  (function(){
+    var t = localStorage.getItem('theme') || 'dark';
+    document.documentElement.setAttribute('data-theme', t);
+    document.addEventListener('DOMContentLoaded', function(){
+      var btn = document.getElementById('theme-toggle');
+      if (btn) btn.textContent = t === 'dark' ? '☀' : '☾';
+    });
+  })();
+</script>
diff --git a/index.php b/index.php
index 3820ea0..1bc7ad0 100644
--- a/index.php
+++ b/index.php
@@ -34,6 +34,7 @@ $update_available = $upstream_version && is_newer_version($upstream_version, APP
 <style>
 <?php include __DIR__ . '/includes/style.php'; ?>
 </style>
+<script>document.documentElement.setAttribute('data-theme',localStorage.getItem('theme')||'dark')</script>
 </head>
 <body>
 <header>
@@ -45,6 +46,7 @@ $update_available = $upstream_version && is_newer_version($upstream_version, APP
     <?php if (auth_enabled()): ?>
       <a href="logout.php" style="color:var(--muted)">Sign out</a>
     <?php endif; ?>
+    <?php include __DIR__ . '/includes/theme_toggle.php'; ?>
   </nav>
 </header>
 <main>
diff --git a/login.php b/login.php
index c8b6c64..015a607 100644
--- a/login.php
+++ b/login.php
@@ -54,6 +54,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
 .login-box form { max-width: 100%; }
 .login-box button[type=submit] { width: 100%; margin-top: .25rem; }
 </style>
+<script>document.documentElement.setAttribute('data-theme',localStorage.getItem('theme')||'dark')</script>
 </head>
 <body>
 <div class="login-wrap">
@@ -75,6 +76,9 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
       <button type="submit">Sign in</button>
     </form>
   </div>
+  <div style="text-align:center;margin-top:.75rem">
+    <?php include __DIR__ . '/includes/theme_toggle.php'; ?>
+  </div>
 </div>
 <?php include __DIR__ . '/includes/footer.php'; ?>
 </body>
diff --git a/nodes.php b/nodes.php
index 7f0cfce..a2e9de3 100644
--- a/nodes.php
+++ b/nodes.php
@@ -60,6 +60,7 @@ if (isset($_GET['edit'])) {
 <style>
 <?php include __DIR__ . '/includes/style.php'; ?>
 </style>
+<script>document.documentElement.setAttribute('data-theme',localStorage.getItem('theme')||'dark')</script>
 </head>
 <body>
 <header>
@@ -71,6 +72,7 @@ if (isset($_GET['edit'])) {
     <?php if (auth_enabled()): ?>
       <a href="logout.php" style="color:var(--muted)">Sign out</a>
     <?php endif; ?>
+    <?php include __DIR__ . '/includes/theme_toggle.php'; ?>
   </nav>
 </header>
 <main>
diff --git a/settings.php b/settings.php
index cd622a9..16feefa 100644
--- a/settings.php
+++ b/settings.php
@@ -58,6 +58,7 @@ $frequent_ip_threshold = (int)get_setting('frequent_ip_threshold', '5');
 <style>
 <?php include __DIR__ . '/includes/style.php'; ?>
 </style>
+<script>document.documentElement.setAttribute('data-theme',localStorage.getItem('theme')||'dark')</script>
 </head>
 <body>
 <header>
@@ -69,6 +70,7 @@ $frequent_ip_threshold = (int)get_setting('frequent_ip_threshold', '5');
     <?php if (auth_enabled()): ?>
       <a href="logout.php" style="color:var(--muted)">Sign out</a>
     <?php endif; ?>
+    <?php include __DIR__ . '/includes/theme_toggle.php'; ?>
   </nav>
 </header>
 <main>
diff --git a/version.php b/version.php
index a7459bc..99d86f6 100644
--- a/version.php
+++ b/version.php
@@ -1,2 +1,2 @@
 <?php
-define('APP_VERSION', '2603.10');
+define('APP_VERSION', '2603.11');
