diff --git a/frontend/src/App.css b/frontend/src/App.css
deleted file mode 100644
index b9d355d..0000000
--- a/frontend/src/App.css
+++ /dev/null
@@ -1,42 +0,0 @@
-#root {
-  max-width: 1280px;
-  margin: 0 auto;
-  padding: 2rem;
-  text-align: center;
-}
-
-.logo {
-  height: 6em;
-  padding: 1.5em;
-  will-change: filter;
-  transition: filter 300ms;
-}
-.logo:hover {
-  filter: drop-shadow(0 0 2em #646cffaa);
-}
-.logo.react:hover {
-  filter: drop-shadow(0 0 2em #61dafbaa);
-}
-
-@keyframes logo-spin {
-  from {
-    transform: rotate(0deg);
-  }
-  to {
-    transform: rotate(360deg);
-  }
-}
-
-@media (prefers-reduced-motion: no-preference) {
-  a:nth-of-type(2) .logo {
-    animation: logo-spin infinite 20s linear;
-  }
-}
-
-.card {
-  padding: 2em;
-}
-
-.read-the-docs {
-  color: #888;
-}
diff --git a/frontend/src/App.jsx b/frontend/src/App.jsx
index 4c6a7e2..4f7a861 100644
--- a/frontend/src/App.jsx
+++ b/frontend/src/App.jsx
@@ -4,6 +4,10 @@ import LoginForm from './components/LoginForm';
 //import RegisterForm from './components/RegisterForm';
 import Md5Tool from './components/Md5Tool';
 import ToolOverview from './components/ToolOverview';
+import './css/base.css';
+import './css/buttons.css';
+import './css/menu.css';
+
 
 function App() {
   const isLoggedIn = localStorage.getItem('token') !== null;
diff --git a/frontend/src/css/base.css b/frontend/src/css/base.css
new file mode 100644
index 0000000..68c670f
--- /dev/null
+++ b/frontend/src/css/base.css
@@ -0,0 +1,28 @@
+/* base.css */
+:root {
+  --bg-color: #121212;
+  --fg-color: #ffffff;
+  --accent-color: #4ea9ff;
+  --font-family: 'Segoe UI', sans-serif;
+  --button-bg: #3f51b5;
+  --button-hover: #5c6bc0;
+}
+
+body {
+  background-color: var(--bg-color);
+  color: var(--fg-color);
+  font-family: var(--font-family);
+  margin: 0;
+  padding: 0;
+}
+
+a {
+  color: var(--accent-color);
+  text-decoration: none;
+}
+
+.container {
+  max-width: 1200px;
+  margin: auto;
+  padding: 2rem;
+}
diff --git a/frontend/src/css/buttons.css b/frontend/src/css/buttons.css
new file mode 100644
index 0000000..b5e5f91
--- /dev/null
+++ b/frontend/src/css/buttons.css
@@ -0,0 +1,14 @@
+/* buttons.css */
+button {
+  background-color: var(--button-bg);
+  color: white;
+  border: none;
+  padding: 0.8rem 1.2rem;
+  border-radius: 6px;
+  cursor: pointer;
+  transition: background-color 0.3s ease;
+}
+
+button:hover {
+  background-color: var(--button-hover);
+}
diff --git a/frontend/src/css/dark.css b/frontend/src/css/dark.css
new file mode 100644
index 0000000..7927ca4
--- /dev/null
+++ b/frontend/src/css/dark.css
@@ -0,0 +1,9 @@
+.dark {
+  --bg-color: #121212;
+  --text-color: #e0e0e0;
+}
+
+body.dark {
+  background-color: var(--bg-color);
+  color: var(--text-color);
+}
diff --git a/frontend/src/index.css b/frontend/src/css/index.css
similarity index 100%
rename from frontend/src/index.css
rename to frontend/src/css/index.css
diff --git a/frontend/src/css/light.css b/frontend/src/css/light.css
new file mode 100644
index 0000000..227f7e9
--- /dev/null
+++ b/frontend/src/css/light.css
@@ -0,0 +1,9 @@
+.light {
+  --bg-color: #ffffff;
+  --text-color: #222222;
+}
+
+body.light {
+  background-color: var(--bg-color);
+  color: var(--text-color);
+}
diff --git a/frontend/src/css/menu.css b/frontend/src/css/menu.css
new file mode 100644
index 0000000..611dda0
--- /dev/null
+++ b/frontend/src/css/menu.css
@@ -0,0 +1,16 @@
+/* menu.css */
+.navbar {
+  background-color: #1e1e2f;
+  color: white;
+  padding: 1rem 2rem;
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  box-shadow: 0 2px 6px rgba(0,0,0,0.4);
+}
+
+.navbar a {
+  color: white;
+  margin-left: 1rem;
+  font-weight: bold;
+}