diff --git a/package.json b/package.json
index dd08534..98c1441 100644
--- a/package.json
+++ b/package.json
@@ -24,6 +24,7 @@
     "@zeit/next-css": "^1.0.1",
     "autoprefixer": "^10.2.4",
     "next": "^10.0.6",
+    "next-themes": "^0.0.10",
     "next-translate": "^1.0.2",
     "popper.js": "^1.16.1",
     "postcss": "^8.2.4",
@@ -33,6 +34,7 @@
   },
   "devDependencies": {
     "@types/node": "^14.14.25",
-    "@types/react": "^17.0.1"
+    "@types/react": "^17.0.1",
+    "typescript": "^4.1.3"
   }
 }
diff --git a/pages/components/LangSelector.js b/pages/components/LangSelector.js
index 52691e7..ddd7041 100644
--- a/pages/components/LangSelector.js
+++ b/pages/components/LangSelector.js
@@ -40,7 +40,7 @@ const Dropdown = ({ color }) => {
     >
       言語 / Languages
       <svg className="-mr-1 ml-2 h-5 w-3" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 20 20" fill="currentColor" aria-hidden="true">
-        <path fillRule="evenodd" d="M5.293 7.293a1 1 0 011.414 0L10 10.586l3.293-3.293a1 1 0 111.414 1.414l-4 4a1 1 0 01-1.414 0l-4-4a1 1 0 010-1.414z" clip-rule="evenodd" />
+        <path fillRule="evenodd" d="M5.293 7.293a1 1 0 011.414 0L10 10.586l3.293-3.293a1 1 0 111.414 1.414l-4 4a1 1 0 01-1.414 0l-4-4a1 1 0 010-1.414z" clipRule="evenodd" />
       </svg>
     </button>
 
diff --git a/tailwind.config.js b/tailwind.config.js
index 7451e2b..951cde9 100644
--- a/tailwind.config.js
+++ b/tailwind.config.js
@@ -1,4 +1,7 @@
 module.exports = {
+  future: {
+    purgeLayersByDefault: true,
+  },
   purge: ['./pages/**/*.{js,ts,jsx,tsx}', './components/**/*.{js,ts,jsx,tsx}'],
   darkMode: "class", // or 'media' or 'class'
   theme: {
diff --git a/yarn.lock b/yarn.lock
index 2606510..57e18da 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1748,6 +1748,11 @@ native-url@0.3.4:
   dependencies:
     querystring "^0.2.0"
 
+next-themes@^0.0.10:
+  version "0.0.10"
+  resolved "https://registry.yarnpkg.com/next-themes/-/next-themes-0.0.10.tgz#86fe5f8a4654416f5d9157993217180174e582b8"
+  integrity sha512-YapL2GVJDooOuGYCYyCywYXRMpulBngG5Qay/HkMK9RyL9xOZ6C3vEgac2dzLWpo3uDVlk+0Qc9XgwGfLHwq/w==
+
 next-translate@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/next-translate/-/next-translate-1.0.2.tgz#af93208221d08a09b96545b2e3d853b69a6ddeb5"
@@ -2859,6 +2864,11 @@ type-fest@^0.7.1:
   resolved "https://registry.yarnpkg.com/type-fest/-/type-fest-0.7.1.tgz#8dda65feaf03ed78f0a3f9678f1869147f7c5c48"
   integrity sha512-Ne2YiiGN8bmrmJJEuTWTLJR32nh/JdL1+PSicowtNb0WFpn59GK8/lfD61bVtzguz7b3PBt74nxpv/Pw5po5Rg==
 
+typescript@^4.1.3:
+  version "4.1.3"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.1.3.tgz#519d582bd94cba0cf8934c7d8e8467e473f53bb7"
+  integrity sha512-B3ZIOf1IKeH2ixgHhj6la6xdwR9QrLC5d1VKeCSY4tvkqhF2eqd9O7txNlS0PO3GrBAFIdr3L1ndNwteUbZLYg==
+
 uniq@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/uniq/-/uniq-1.0.1.tgz#b31c5ae8254844a3a8281541ce2b04b865a734ff"