Adding to Mercury Modules
It is possible to create custom controller files, display files and functions within existing modules. Even if the functions or display files do not exist in the Mercury core you can write your own controller files and they will be picked up by the inbound request handler before it checks the core files. To this end you can also create your own custom files and display files. While this is possible it is not really recommended. It is probably better to make your own custom module and implement your own functionality that way. This preserves the integrity of the Mercury core and reduces the likelihood of unforeseen conflicts down the road that might occur if the core ends up with files named the same as your customizations.