dictionary example

sandbox/will/basic.css

@@ -18,6 +18,7 @@ App > Screen {
   layers: base sidebar;  
   layout: vertical;
   overflow: hidden;
+
 }
 
 #tree-container {

sandbox/will/basic.py

@@ -104,9 +104,11 @@ class Success(Static):
         return Text("This is a success  message", justify="center")
 
 
-class BasicApp(App, css_path="basic.css"):
+class BasicApp(App):
     """A basic app demonstrating CSS"""
 
+    CSS_PATH = "basic.css"
+
     def on_load(self):
         """Bind keys here."""
         self.bind("s", "toggle_class('#sidebar', '-active')", description="Sidebar")