diff --git a/src/contentScripts/communityConsole/darkTheme/darkTheme.js b/src/contentScripts/communityConsole/darkTheme/darkTheme.js
new file mode 100644
index 0000000..7bd4ba6
--- /dev/null
+++ b/src/contentScripts/communityConsole/darkTheme/darkTheme.js
@@ -0,0 +1,56 @@
+import {MDCTooltip} from '@material/tooltip';
+
+import {createPlainTooltip} from '../../../common/tooltip.js';
+import {createExtBadge} from '../utils/common.js';
+
+
+export function injectDarkThemeButton(rightControl, previousDarkThemeOption) {
+  var darkThemeSwitch = document.createElement('material-button');
+  darkThemeSwitch.classList.add('TWPT-dark-theme', 'TWPT-btn--with-badge');
+  darkThemeSwitch.setAttribute('button', '');
+
+  darkThemeSwitch.addEventListener('click', () => {
+    chrome.storage.sync.get(null, currentOptions => {
+      currentOptions.ccdarktheme_switch_status = !previousDarkThemeOption;
+      chrome.storage.sync.set(currentOptions, () => {
+        location.reload();
+      });
+    });
+  });
+
+  var switchContent = document.createElement('div');
+  switchContent.classList.add('content');
+
+  var icon = document.createElement('material-icon');
+
+  var i = document.createElement('i');
+  i.classList.add('material-icon-i', 'material-icons-extended');
+  i.textContent = 'brightness_4';
+
+  icon.appendChild(i);
+  switchContent.appendChild(icon);
+  darkThemeSwitch.appendChild(switchContent);
+
+  let badgeContent, badgeTooltip;
+  [badgeContent, badgeTooltip] = createExtBadge();
+
+  darkThemeSwitch.appendChild(badgeContent);
+
+  rightControl.style.width =
+      (parseInt(window.getComputedStyle(rightControl).width) + 58) + 'px';
+  rightControl.insertAdjacentElement('afterbegin', darkThemeSwitch);
+
+  createPlainTooltip(
+      switchContent, chrome.i18n.getMessage('inject_ccdarktheme_helper'));
+  new MDCTooltip(badgeTooltip);
+}
+
+export function isDarkThemeOn(options) {
+  if (!options.ccdarktheme) return false;
+
+  if (options.ccdarktheme_mode == 'switch')
+    return options.ccdarktheme_switch_status;
+
+  return window.matchMedia &&
+      window.matchMedia('(prefers-color-scheme: dark)').matches;
+}