diff --git a/data_visualization/css/theme.css b/data_visualization/css/theme.css
new file mode 100644
index 0000000..d99dadf
--- /dev/null
+++ b/data_visualization/css/theme.css
@@ -0,0 +1,60 @@
+:root {
+  /* Theme Variables */
+  --color-primary: #0057ff;
+  --color-secondary: #26a69a;
+  --color-accent: #ffca28;
+
+  --background-main: #ffffff;
+  --background-surface: #f6f8fa;
+  --text-primary: #1a1a1a;
+  --text-secondary: #4a4a4a;
+  --border-color: #e0e0e0;
+
+  --spacing-xs: 0.25rem;
+  --spacing-sm: 0.5rem;
+  --spacing-md: 1rem;
+  --spacing-lg: 2rem;
+
+  --font-base: 'system-ui', sans-serif;
+  --transition-default: 0.3s ease-in-out;
+}
+
+.dark-mode {
+  --background-main: #121212;
+  --background-surface: #1e1e1e;
+  --text-primary: #f0f0f0;
+  --text-secondary: #cccccc;
+  --border-color: #333333;
+
+  --color-primary: #82b1ff;
+  --color-secondary: #80cbc4;
+  --color-accent: #ffd54f;
+}
+
+body {
+  background-color: var(--background-main);
+  color: var(--text-primary);
+  font-family: var(--font-base);
+  transition: background-color var(--transition-default), color var(--transition-default);
+}
+
+.dark-mode body {
+  background-color: var(--background-main);
+  color: var(--text-primary);
+}
+
+/* Footer copyright styling */
+footer {
+  text-align: center;
+  font-size: 0.875rem;
+  padding: var(--spacing-md);
+  color: var(--text-secondary);
+}
+
+footer::after {
+  content: '© 2026 Donau2Space.de';
+  display: block;
+  margin-top: var(--spacing-sm);
+  font-style: italic;
+  opacity: 0.7;
+}
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