Expand on hidelines documentation.

Author: ehuss

guide/src/format/mdbook.md

@@ -2,10 +2,11 @@
 
 ## Hiding code lines
 
-There is a feature in mdBook that lets you hide code lines by prepending them
-with a `#` [like you would with Rustdoc][rustdoc-hide].
+There is a feature in mdBook that lets you hide code lines by prepending them with a specific prefix.
 
-[rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/documentation-tests.html#hiding-portions-of-the-example
+For the Rust language, you can use the `#` character as a prefix which will hide lines [like you would with Rustdoc][rustdoc-hide].
+
+[rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/write-documentation/documentation-tests.html#hiding-portions-of-the-example
 
 ```bash
 # fn main() {
@@ -27,7 +28,7 @@ Will render as
 # }
 ```
 
-The code block has an eyeball icon (<i class="fa fa-eye"></i>) which will toggle the visibility of the hidden lines.
+When you tap or hover the mouse over the code block, there will be an eyeball icon (<i class="fa fa-eye"></i>) which will toggle the visibility of the hidden lines.
 
 By default, this only works for code examples that are annotated with `rust`.
 However, you can define custom prefixes for other languages by adding a new line-hiding prefix in your `book.toml` with the language name and prefix character(s):
@@ -59,7 +60,7 @@ nothidden():
 
 This behavior can be overridden locally with a different prefix. This has the same effect as above:
 
-~~~bash
+~~~markdown
 ```python,hidelines=!!!
 !!!hidden()
 nothidden():