diff --git a/open-isle-cli/src/assets/global.css b/open-isle-cli/src/assets/global.css
index d9d869ad5..e33499acb 100644
--- a/open-isle-cli/src/assets/global.css
+++ b/open-isle-cli/src/assets/global.css
@@ -5,19 +5,36 @@
   --header-height: 60px;
   --header-background-color: white;
   --header-border-color: lightgray;
+  --header-text-color: black;
   --menu-background-color: white;
   --menu-border-color: lightgray;
   --menu-selected-background-color: rgba(208, 250, 255, 0.659);
+  --menu-text-color: black;
   --scroller-background-color: rgba(130, 175, 180, 0.5);
   --normal-background-color: rgb(241, 241, 241);
+  --text-color: black;
   --menu-width: 200px;
   --page-max-width: 1200px;
 }
 
+[data-theme='dark'] {
+  --header-background-color: #2b2b2b;
+  --header-border-color: #555;
+  --header-text-color: white;
+  --menu-background-color: #333;
+  --menu-border-color: #555;
+  --menu-selected-background-color: rgba(255, 255, 255, 0.1);
+  --menu-text-color: white;
+  --normal-background-color: #121212;
+  --text-color: #eee;
+}
+
 body {
   margin: 0;
   padding: 0;
   font-family: 'Roboto', sans-serif;
+  background-color: var(--normal-background-color);
+  color: var(--text-color);
 }
 
 
diff --git a/open-isle-cli/src/components/MenuComponent.vue b/open-isle-cli/src/components/MenuComponent.vue
index 652e253fe..4ce27c9b3 100644
--- a/open-isle-cli/src/components/MenuComponent.vue
+++ b/open-isle-cli/src/components/MenuComponent.vue
@@ -21,8 +21,8 @@
       </div>
 
       <div class="menu-footer">
-        <div class="menu-footer-btn" @click="$emit('toggle-dark-mode')">
-          <i class="fas fa-moon"></i>
+        <div class="menu-footer-btn" @click="cycleTheme">
+          <i :class="iconClass"></i>
         </div>
       </div>
     </nav>
@@ -30,6 +30,7 @@
 </template>
 
 <script>
+import { themeState, cycleTheme, ThemeMode } from '../utils/theme'
 export default {
   name: 'MenuComponent',
   props: {
@@ -37,7 +38,20 @@ export default {
       type: Boolean,
       default: true
     }
-  }
+  },
+  computed: {
+    iconClass() {
+      switch (themeState.mode) {
+        case ThemeMode.DARK:
+          return 'fas fa-moon'
+        case ThemeMode.LIGHT:
+          return 'fas fa-sun'
+        default:
+          return 'fas fa-desktop'
+      }
+    }
+  },
+  methods: { cycleTheme }
 }
 </script>
 
diff --git a/open-isle-cli/src/main.js b/open-isle-cli/src/main.js
index 7dba5ab39..7e61eacf6 100644
--- a/open-isle-cli/src/main.js
+++ b/open-isle-cli/src/main.js
@@ -6,6 +6,7 @@ import Toast, { POSITION } from 'vue-toastification'
 import 'vue-toastification/dist/index.css'
 import { useToast } from 'vue-toastification'
 import { checkToken, clearToken } from './utils/auth'
+import { initTheme } from './utils/theme'
 
 // Configurable API domain and port
 export const API_DOMAIN = 'http://127.0.0.1'
@@ -14,6 +15,8 @@ export const API_BASE_URL = API_PORT ? `${API_DOMAIN}:${API_PORT}` : API_DOMAIN
 export const GOOGLE_CLIENT_ID = '777830451304-nt8afkkap18gui4f9entcha99unal744.apps.googleusercontent.com'
 export const toast = useToast()
 
+initTheme()
+
 const app = createApp(App)
 app.use(router)
 app.use(Toast, { position: POSITION.TOP_RIGHT })
diff --git a/open-isle-cli/src/utils/theme.js b/open-isle-cli/src/utils/theme.js
new file mode 100644
index 000000000..cd209d571
--- /dev/null
+++ b/open-isle-cli/src/utils/theme.js
@@ -0,0 +1,52 @@
+import { reactive } from 'vue'
+
+export const ThemeMode = {
+  SYSTEM: 'system',
+  LIGHT: 'light',
+  DARK: 'dark'
+}
+
+const THEME_KEY = 'theme-mode'
+
+export const themeState = reactive({
+  mode: ThemeMode.SYSTEM
+})
+
+function apply(mode) {
+  const root = document.documentElement
+  if (mode === ThemeMode.SYSTEM) {
+    root.dataset.theme = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'
+  } else {
+    root.dataset.theme = mode
+  }
+}
+
+export function initTheme() {
+  const saved = localStorage.getItem(THEME_KEY)
+  if (saved && Object.values(ThemeMode).includes(saved)) {
+    themeState.mode = saved
+  }
+  apply(themeState.mode)
+}
+
+export function setTheme(mode) {
+  if (!Object.values(ThemeMode).includes(mode)) return
+  themeState.mode = mode
+  localStorage.setItem(THEME_KEY, mode)
+  apply(mode)
+}
+
+export function cycleTheme() {
+  const modes = [ThemeMode.SYSTEM, ThemeMode.LIGHT, ThemeMode.DARK]
+  const index = modes.indexOf(themeState.mode)
+  const next = modes[(index + 1) % modes.length]
+  setTheme(next)
+}
+
+if (window.matchMedia) {
+  window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', () => {
+    if (themeState.mode === ThemeMode.SYSTEM) {
+      apply(ThemeMode.SYSTEM)
+    }
+  })
+}