Update app.py

app.py

@@ -251,10 +251,10 @@ examples = [
 css = """
 #col-container {
     margin: 0 auto;
-    max-width: 640px;
+    max-width: 768px;
 }
 body {
-  background-color: darkblue;
+  background-color: blue;
 }
 """