diff --git a/app.js b/app.js
index d3229f0..a3f7a8c 100644
--- a/app.js
+++ b/app.js
@@ -719,7 +719,15 @@ const TICKER_COLORS_LIGHT = [
   '#3498db', '#1abc9c', '#b8860b', '#8e44ad', '#e74c3c'
 ];
 
-const isLightTheme = window.matchMedia('(prefers-color-scheme: light)').matches;
+const THEME_KEY = 'numnum-theme';
+
+function getPreferredTheme() {
+  const saved = localStorage.getItem(THEME_KEY);
+  if (saved === 'light' || saved === 'dark') return saved;
+  return window.matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
+}
+
+const isLightTheme = getPreferredTheme() === 'light';
 const TICKER_COLORS = isLightTheme ? TICKER_COLORS_LIGHT : TICKER_COLORS_DARK;
 
 const TICKER_SYSTEMS = [
@@ -776,6 +784,19 @@ langSelect.addEventListener('change', () => {
 
 applyTranslations();
 
+function applyTheme(theme) {
+  document.documentElement.dataset.theme = theme;
+  document.getElementById('theme-toggle').textContent = theme === 'dark' ? '\u2600' : '\u263E';
+}
+
+applyTheme(getPreferredTheme());
+
+document.getElementById('theme-toggle').addEventListener('click', () => {
+  const next = document.documentElement.dataset.theme === 'dark' ? 'light' : 'dark';
+  localStorage.setItem(THEME_KEY, next);
+  applyTheme(next);
+});
+
 let deferredPrompt = null;
 
 window.addEventListener('beforeinstallprompt', (e) => {
diff --git a/index.html b/index.html
index 14dbab1..2435b8d 100644
--- a/index.html
+++ b/index.html
@@ -24,10 +24,13 @@
           <div class="ticker" id="ticker"></div>
         </div>
         <button class="btn btn-primary btn-large" id="btn-start" data-i18n="startGame">Start Game</button>
-        <select id="lang-select" class="lang-select">
-          <option value="en">English</option>
-          <option value="ru">Русский</option>
-        </select>
+        <div class="menu-controls">
+          <select id="lang-select" class="lang-select">
+            <option value="en">English</option>
+            <option value="ru">Русский</option>
+          </select>
+          <button id="theme-toggle" class="theme-toggle" aria-label="Toggle theme"></button>
+        </div>
         <button class="btn btn-secondary btn-large hidden" id="btn-install" data-i18n="installApp">Install App</button>
       </div>
     </div>
diff --git a/styles.css b/styles.css
index bb33838..d0668fc 100644
--- a/styles.css
+++ b/styles.css
@@ -37,6 +37,34 @@
   }
 }
 
+html[data-theme="dark"] {
+  --bg: #1a1a2e;
+  --bg-light: #16213e;
+  --bg-card: #0f3460;
+  --accent: #e94560;
+  --accent-hover: #ff6b81;
+  --accent-secondary: #ff9a56;
+  --text: #eaeaea;
+  --text-dim: #a0a0b0;
+  --correct: #2ecc71;
+  --incorrect: #e74c3c;
+  --border: rgba(255,255,255,0.08);
+}
+
+html[data-theme="light"] {
+  --bg: #f5f5f5;
+  --bg-light: #ffffff;
+  --bg-card: #ffffff;
+  --accent: #e94560;
+  --accent-hover: #d63851;
+  --accent-secondary: #f09040;
+  --text: #1a1a2e;
+  --text-dim: #555566;
+  --correct: #27ae60;
+  --incorrect: #c0392b;
+  --border: #d0d0d0;
+}
+
 @font-face {
   font-family: 'Ponomar';
   src: url('Ponomar-Regular.woff') format('woff');
@@ -127,6 +155,35 @@ body {
   display: block;
 }
 
+.menu-controls {
+  display: flex;
+  gap: 8px;
+  width: 100%;
+  max-width: 320px;
+}
+
+.menu-controls .lang-select {
+  flex: 1;
+  width: auto;
+  max-width: none;
+  margin: 0;
+}
+
+.theme-toggle {
+  width: 44px;
+  height: 44px;
+  flex-shrink: 0;
+  background: var(--bg-light);
+  color: var(--text);
+  border: 2px solid var(--border);
+  border-radius: 8px;
+  font-size: 1.3rem;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
 .ticker {
   display: inline-block;
   white-space: nowrap;