fix styles examples, box model docs

docs/examples/guide/dom1.py

@@ -6,3 +6,5 @@ class ExampleApp(App):
 
 
 app = ExampleApp()
+if __name__ == "__main__":
+    app.run()

docs/examples/guide/dom2.py

@@ -9,3 +9,5 @@ class ExampleApp(App):
 
 
 app = ExampleApp()
+if __name__ == "__main__":
+    app.run()

docs/examples/guide/dom3.py

@@ -21,3 +21,5 @@ class ExampleApp(App):
 
 
 app = ExampleApp()
+if __name__ == "__main__":
+    app.run()

docs/examples/guide/dom4.css

@@ -2,9 +2,9 @@
 /* The top level dialog (a Container) */
 #dialog {
     margin: 4 8;
-    background: darkblue 20%;
-    color: darkblue;
-    border: tall darkblue;
+    background: $primary;
+    color: $text-primary;
+    border: tall $text-primary;
     padding: 1 2;
 }
 

docs/examples/guide/styles/screen.py

@@ -0,0 +1,12 @@
+from textual.app import App
+
+
+class ScreenApp(App):
+    def on_mount(self) -> None:
+        self.screen.styles.background = "darkblue"
+        self.screen.styles.border = ("heavy", "white")
+
+
+app = ScreenApp()
+if __name__ == "__main__":
+    app.run()