Update app.py

app.py

@@ -141,7 +141,7 @@ body, html {
 }
 
 #main-container {
-    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+    background: linear-gradient(135deg, #1a1d1f 0%, #764ba2 100%);
     min-height: 100vh;
 }