Update intro.rst

extension-docs/intro.rst

@@ -42,19 +42,23 @@ You can see there what the special comment string is for each type of class (Geo
 While it is beyond the scope of this User Guide to teach C++ programming, one issue that has come up a few times might be worth mentioning.
 Any time you see an example use a variable with a name starting with f, such as fEnvelopeLog or fEnevelopePhys,
 you should be careful not to redeclare your own local version of this variable.
-So go ahead and set them as::
+So go ahead and set them as
+
+.. code-block:: c++
 
 	fEnvelopeLog = CreateLogicalVolume(something);
 	fEnvelopePhys = CreatePhysicalVolume(fEnvelopeLog);
 
-Do <b>not</b> set them as::
+Do **not** set them as
+
+.. code-block:: c++
 
 	G4LogicalVolume* fEnvelopeLog = CreateLogicalVolume(something);
 	G4VPhysicalVolume* fEnvelopePhys = CreatePhysicalVolume(fEnvelopeLog);
 
 The latter case would create a new, local copy of the variable, and would mean that when the base classes go to do other work with
 these objects, they would find them to be unset, giving various crashes (probably segmentation faults).
-You can read more elsewhere about this general topic, <a href="https://en.wikipedia.org/wiki/Variable_shadowing">Variable Shadowing</a>.
+You can read more elsewhere about this general topic, Variable Shadowing <https://en.wikipedia.org/wiki/Variable_shadowing>.
 
 To build your new TOPAS executable that incorporates all of your extensions, you run CMake with an argument that tells it the location of your extensions. Your extensions then coexist with the rest of the TOPAS code.