Shuffle sections around.

docs/guide/app.md

@@ -117,7 +117,7 @@ When you first run this you will get a blank screen. Press any key to add the we
 ```{.textual path="docs/examples/app/widgets02.py" press="a,a,a,down,down,down,down,down,down,_,_,_,_,_,_"}
 ```
 
-### Exiting
+## Exiting
 
 An app will run until you call [App.exit()][textual.app.App.exit] which will exit application mode and the [run][textual.app.App.run] method will return. If this is the last line in your code you will return to the command prompt.
 
@@ -134,7 +134,7 @@ Running this app will give you the following:
 
 Clicking either of those buttons will exit the app, and the `run()` method will return either `"yes"` or `"no"` depending on button clicked.
 
-#### Return type
+### Return type
 
 You may have noticed that we subclassed `App[str]` rather than the usual `App`.
 
@@ -148,42 +148,8 @@ The addition of `[str]` tells mypy that `run()` is expected to return a string.
 
     Type annotations are entirely optional (but recommended) with Textual.
 
-## Customising your app
 
-### Title and subtitle
+## CSS
-
-Textual applications have a `title` attribute that represents the name of your application and a `sub_title` attribute that gives additional context for it.
-These attributes can be displayed to the user if your application has a widget `Header` and there are two ways in which you can customize them if you don't want to run with the default values.
-
-By default, the title of your application matches the name of the application class and the subtitle is empty.
-However, you can override those defaults by setting the class attributes `TITLE` and `SUB_TITLE`, as shown below.
-Remember that you need the built-in widget `Header` to make the title and the subtitle visible in our app.
-
-```py title="question_title01.py" hl_lines="6-7 10"
---8<-- "docs/examples/app/question_title01.py"
-```
-
-The app title and subtitle are displayed at the top of the application in the header:
-
-```{.textual path="docs/examples/app/question_title01.py"}
-```
-
-On top of being able to define a default title and a default subtitle for a given application class, each _instance_ of your application class has two attributes `title` and `sub_title` that can be used to modify the title and subtitle of said instance application.
-
-For example, the application shown below changes its title and subtitle as soon as the application is instantiated.
-
-```py title="question_title02.py" hl_lines="19-21"
---8<-- "docs/examples/app/question_title02.py"
-```
-
-If you run the app shown above and if you press a key, the title and subtitle update accordingly.
-
-For example, if you press `t`, your application will look as shown below:
-
-```{.textual path="docs/examples/app/question_title02.py" press="t"}
-```
-
-### CSS
 
 Textual apps can reference [CSS](CSS.md) files which define how your app and widgets will look, while keeping your Python code free of display related code (which tends to be messy).
 
@@ -220,6 +186,40 @@ Here's the question app with classvar CSS:
 ```
 
 
+## Title and subtitle
+
+Textual applications have a `title` attribute that represents the name of your application and a `sub_title` attribute that gives additional context for it.
+These attributes can be displayed to the user if your application has a widget `Header` and there are two ways in which you can customize them if you don't want to run with the default values.
+
+By default, the title of your application matches the name of the application class and the subtitle is empty.
+However, you can override those defaults by setting the class attributes `TITLE` and `SUB_TITLE`, as shown below.
+Remember that you need the built-in widget `Header` to make the title and the subtitle visible in our app.
+
+```py title="question_title01.py" hl_lines="6-7 10"
+--8<-- "docs/examples/app/question_title01.py"
+```
+
+The app title and subtitle are displayed at the top of the application in the header:
+
+```{.textual path="docs/examples/app/question_title01.py"}
+```
+
+On top of being able to define a default title and a default subtitle for a given application class, each _instance_ of your application class has two attributes `title` and `sub_title` that can be used to modify the title and subtitle of said instance application.
+
+For example, the application shown below changes its title and subtitle as soon as the application is instantiated.
+
+```py title="question_title02.py" hl_lines="19-21"
+--8<-- "docs/examples/app/question_title02.py"
+```
+
+If you run the app shown above and if you press a key, the title and subtitle update accordingly.
+
+For example, if you press `t`, your application will look as shown below:
+
+```{.textual path="docs/examples/app/question_title02.py" press="t"}
+```
+
+
 ## What's next
 
 In the following chapter we will learn more about how to apply styles to your widgets and app.