diff --git a/frontend/src/pages/setup.rs b/frontend/src/pages/setup.rs
index 2f8c532..41a7cf6 100644
--- a/frontend/src/pages/setup.rs
+++ b/frontend/src/pages/setup.rs
@@ -182,7 +182,7 @@ pub fn initial_admin_setup() -> Html {
     };
 
     html! {
-        <div class="setup-container">
+        <div class="setup-container rundbg">
             <div class="setup-box">
                 <h1>{ "Initial Admin Setup" }</h1>
                 <p>{ "Create your first administrator account" }</p>
diff --git a/frontend/src/pages/sidebar.rs b/frontend/src/pages/sidebar.rs
index ade0e6c..0fe636d 100644
--- a/frontend/src/pages/sidebar.rs
+++ b/frontend/src/pages/sidebar.rs
@@ -390,7 +390,7 @@ pub fn sidebar() -> Html {
                         <TicketMenu/>
                         <li class="logout-item">
                             <button
-                                class="logout-button"
+                                class="sidebar-button"
                                 onclick={on_logout.clone()}
                             >
                                 { "Logout" }
@@ -417,8 +417,9 @@ pub fn sidebar() -> Html {
                         <Link<crate::Route> to={crate::Route::Diagnostics}>{ "Statistiken" }</Link<crate::Route>>
                         <Link<crate::Route> to={crate::Route::ArchivedTickets}>{ "Archiv" }</Link<crate::Route>>
                         <li class="logout-item">
+                            <crate::darkmode::ThemeToggle/>
                             <button
-                                class="logout-button"
+                                class="sidebar-button"
                                 onclick={on_logout.clone()}
                             >
                                 { "Logout" }
diff --git a/frontend/src/styles/_mixins.scss b/frontend/src/styles/_mixins.scss
index 2837238..09d438d 100644
--- a/frontend/src/styles/_mixins.scss
+++ b/frontend/src/styles/_mixins.scss
@@ -4,5 +4,5 @@
   backgroud: #fff;
   border-radius: &border-radius;
   box-shadow: 0 1px 3px rgba(0,0,0,0.06);
-  padding: $spacing-md;
+  padding: var(--spacing-md);
 }
diff --git a/frontend/src/styles/_utilities.scss b/frontend/src/styles/_utilities.scss
index ed174a8..5a414b7 100644
--- a/frontend/src/styles/_utilities.scss
+++ b/frontend/src/styles/_utilities.scss
@@ -1,6 +1,6 @@
 @use "variables" as *;
 
 .u-hidden { display: none !important; }
-.u-gap-sm { gap: $spacing-sm; }
-.text-muted { color: $color-muted; }
+.u-gap-sm { gap: var(--spacing-sm); }
+.text-muted { color: var(--color-muted); }
 
diff --git a/frontend/src/styles/_variables.scss b/frontend/src/styles/_variables.scss
index 1e0b0a1..79d5419 100644
--- a/frontend/src/styles/_variables.scss
+++ b/frontend/src/styles/_variables.scss
@@ -1,8 +1,22 @@
-$color-bg: #ffffff;
-$color-sidebar: #570000;
-$color-accent: #2563eb;
-$color-muted: #6b7280;
-$spacing-sm: 8px;
-$spacing-md: 16px;
-$border-radius: 6px;
-$rundbgbackgroundcolor: #a0a0a0;
+:root {
+  --color-bg: #ffffff;
+  --color-sidebar: #570000;
+  --color-accent: #2563eb;
+  --color-muted: #6b7280;
+  --spacing-sm: 8px;
+  --spacing-md: 16px;
+  --border-radius: 6px;
+  --rundbgbackgroundcolor: #a0a0a0;
+}
+
+[data-theme='dark'] {
+  --color-bg: #000000;
+  --color-sidebar: #570000;
+  --color-accent: #2563eb;
+  --color-muted: #6b7280;
+  --spacing-sm: 8px;
+  --spacing-md: 16px;
+  --border-radius: 6px;
+  --rundbgbackgroundcolor: #a0a0a0;
+
+}
diff --git a/frontend/src/styles/components/_diagnostics.scss b/frontend/src/styles/components/_diagnostics.scss
index 7816a2e..fa2d02d 100644
--- a/frontend/src/styles/components/_diagnostics.scss
+++ b/frontend/src/styles/components/_diagnostics.scss
@@ -4,17 +4,17 @@
 .diagnostics-container {
   display: flex;
   flex-direction: column;
-  gap: $spacing-md;
+  gap: var(--spacing-md);
 }
 
 .diagnostics-section {
-  background-color: $color-bg;
-  border-radius: $border-radius;
-  padding: $spacing-md;
+  background-color: var(--color-bg);
+  border-radius: var(--border-radius);
+  padding: var(--spacing-md);
   box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
 
   h3 {
-    margin: 0 0 $spacing-md 0;
+    margin: 0 0 var(--spacing-md) 0;
     color: #1f2937;
     font-size: 1.1rem;
     font-weight: 600;
@@ -26,7 +26,7 @@
   flex-direction: column;
   gap: 12px;
   border: 1px solid #e5e7eb;
-  border-radius: $border-radius;
+  border-radius: var(--border-radius);
   background-color: #f9fafb;
 }
 
@@ -35,7 +35,7 @@
   gap: 12px;
   align-items: flex-end;
   height: 205px;
-  padding: $spacing-md;
+  padding: var(--spacing-md);
   overflow-x: auto;
   padding-bottom: 0px;
 }
@@ -51,7 +51,7 @@
 
   .bar {
     width: 100%;
-    background-color: $color-accent;
+    background-color: var(--color-accent);
     border-radius: 4px 4px 0 0;
     transition: background-color 0.2s ease;
 
@@ -64,7 +64,7 @@
 .weekday-labels {
   display: flex;
   gap: 12px;
-  padding: $spacing-md;
+  padding: var(--spacing-md);
   padding-top: 0;
   overflow-x: auto;
 
@@ -83,7 +83,7 @@
 
     .value {
       font-size: 11px;
-      color: $color-muted;
+      color: var(--color-muted);
     }
   }
 }
@@ -92,9 +92,9 @@
   display: flex;
   flex-direction: column;
   gap: 12px;
-  padding: $spacing-md;
+  padding: var(--spacing-md);
   border: 1px solid #e5e7eb;
-  border-radius: $border-radius;
+  border-radius: var(--border-radius);
   background-color: #f9fafb;
 }
 
@@ -117,7 +117,7 @@
 
     .room-count {
       font-size: 12px;
-      color: $color-muted;
+      color: var(--color-muted);
       font-weight: 500;
     }
   }
diff --git a/frontend/src/styles/components/_sidebar.scss b/frontend/src/styles/components/_sidebar.scss
index 1bd52a5..45e18fb 100644
--- a/frontend/src/styles/components/_sidebar.scss
+++ b/frontend/src/styles/components/_sidebar.scss
@@ -3,16 +3,16 @@
 
 .sidebar {
   width: 260px;
-  background: $color-sidebar;
+  background: var(--color-sidebar);
   color: #fffefe;
   min-height: 100%;
-  padding: $spacing-md;
+  padding: var(--spacing-md);
   display: flex;
   flex-direction: column;
 
  
 
-  ul { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: $spacing-sm; flex: 1; }
+  ul { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: var(--spacing-sm); flex: 1; }
 
   a, .menu-toggle {
     color: #ffffff;
@@ -36,10 +36,10 @@
   .logout-item {
     margin-top: auto;
     border-top: 1px solid rgba(255,255,255,0.1);
-    padding-top: $spacing-sm;
+    padding-top: var(--spacing-sm);
   }
 
-  .logout-button {
+  .sidebar-button {
     background: rgba(255, 93, 43, 0.527);
     color: #ffffff;
     border: 1px solid rgba(255, 255, 255, 0.801);
@@ -52,7 +52,7 @@
     &:active { background: rgba(255,255,255,0.2); }
   }
 
-  &.user { width: 220px; background: darken($color-sidebar, 6%); }
+  &.user { width: 220px; background: darken(#570000, 6%); }
 
   .home-svg {
       width: 24px;
diff --git a/frontend/src/styles/components/_tickets.scss b/frontend/src/styles/components/_tickets.scss
index 623d8be..81d22db 100644
--- a/frontend/src/styles/components/_tickets.scss
+++ b/frontend/src/styles/components/_tickets.scss
@@ -3,12 +3,12 @@
 
 .ticket-card {
   @include card();
-  border-left: 4px solid $color-accent;
+  border-left: 4px solid var(--color-accent);
   display: flex;
   flex-direction: column;
-  gap: $spacing-sm;
+  gap: var(--spacing-sm);
 
-  .meta { color: $color-muted; font-size: 0.9rem; }
+  .meta { color: var(--color-muted); font-size: 0.9rem; }
   .title { font-weight: 600; }
 
 }
@@ -17,7 +17,7 @@
   max-width: auto;
   margin:0 0;
   background-color: #90ff82;
-  background-color: $rundbgbackgroundcolor;
+  background-color: var(--rundbgbackgroundcolor);
   padding-bottom: 8px;
   color: white;
   padding-left: 8px;
diff --git a/frontend/src/styles/main.scss b/frontend/src/styles/main.scss
index 610a2be..e8ac940 100644
--- a/frontend/src/styles/main.scss
+++ b/frontend/src/styles/main.scss
@@ -9,7 +9,7 @@
 @use "components/icon";
 
 body {
-  background: variables.$color-bg;
+  background: var(--color-bg);
   font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
   color: #111827;
   margin: 0;
@@ -37,7 +37,7 @@ body {
   min-width: 0;
   height: 100%;
   overflow-y: auto;
-  padding: variables.$spacing-md;
+  padding: var(--spacing-md);
   box-sizing: border-box;
 }
 
@@ -53,7 +53,7 @@ body {
     box-sizing: border-box;
   }
   .sidebar.open { left: 0; }
-  .content { margin-left: 0; padding: variables.$spacing-md; box-sizing: border-box; }
+  .content { margin-left: 0; padding: var(--spacing-md); box-sizing: border-box; }
 }
 
 .rundbg {
@@ -62,7 +62,7 @@ body {
   flex-direction: column;
   max-width: 60%;
   margin: 0 auto;
-  background-color: variables.$rundbgbackgroundcolor;
+  background-color: var(--rundbgbackgroundcolor);
   padding-bottom: 96px;
   padding-left: 32px;
   padding-right: 32px;