diff --git a/data_visualization_web_ui/css/base.css b/data_visualization_web_ui/css/base.css
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+++ b/data_visualization_web_ui/css/base.css
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+/* =====================================
+   CSS Reset und Variablen
+   ===================================== */
+
+:root {
+  /* Farbvariablen */
+  --color-bg: #f6f8fa;
+  --color-text: #1b1b1b;
+  --color-primary: #2a6bb0;
+  --color-accent: #35823f;
+  --color-border: #d0d7de;
+  
+  /* Typografie und Abstände */
+  --font-base: 'Segoe UI', system-ui, sans-serif;
+  --font-size-base: 16px;
+  --line-height-base: 1.5;
+  --spacing-xs: 0.25rem;
+  --spacing-sm: 0.5rem;
+  --spacing-md: 1rem;
+  --spacing-lg: 1.5rem;
+  --border-radius: 4px;
+  
+  /* Breakpoints */
+  --breakpoint-sm: 640px;
+  --breakpoint-md: 1024px;
+  --breakpoint-lg: 1440px;
+}
+
+/* Reset */
+* {
+  margin: 0;
+  padding: 0;
+  box-sizing: border-box;
+}
+
+html, body {
+  height: 100%;
+  font-family: var(--font-base);
+  font-size: var(--font-size-base);
+  line-height: var(--line-height-base);
+  color: var(--color-text);
+  background-color: var(--color-bg);
+}
+
+body {
+  display: flex;
+  flex-direction: column;
+  min-height: 100vh;
+}
+
+/* =====================================
+   App-Shell
+   ===================================== */
+
+.app-shell {
+  display: grid;
+  grid-template-rows: auto 1fr auto;
+  grid-template-columns: 100%;
+  min-height: 100vh;
+  width: 100%;
+}
+
+.app-shell header,
+.app-shell footer {
+  background-color: var(--color-primary);
+  color: #fff;
+  padding: var(--spacing-md);
+}
+
+.app-shell main {
+  padding: var(--spacing-md);
+  display: flex;
+  flex-direction: column;
+  gap: var(--spacing-md);
+}
+
+.app-shell footer {
+  text-align: center;
+  font-size: 0.875rem;
+}
+
+.app-shell footer::after {
+  content: "© 2026 Donau2Space.de";
+  display: block;
+  margin-top: var(--spacing-xs);
+}
+
+/* Responsiveness */
+@media (min-width: var(--breakpoint-md)) {
+  .app-shell main {
+    padding: var(--spacing-lg);
+    gap: var(--spacing-lg);
+  }
+}
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