Overriding Display Files in Mercury
Mercury provides a lot of functionality but the odds are that you will want to change the appearance of some of the pages at some point. This is where Mercury gets exciting!
Since all of the logic is done in controller files and all of the processing and querying is done in the functions it means that the display files are very simple. As discussed in previous sections Mercury includes the display files in such a way that it is a piece of cake for a designer to take an existing display file (from the core), update it and place it into a given site as a display override.
An Example
The basic users modules calls a display file using the d("users", "login-form") command. On a new site with no overrides Mercury will not find a custom file and will use the display file in mercury/users/display/login-form.php.
The easiest way to customize this is to copy the file from the location above into the html/mercury/users/display/login-form.php and make some updates to it there. You will probably want to keep variable names and link/form paths the same but you can completely change the appearance to anything you want. That said, so long as the links and forms continue to function in the same way you don't have to copy from a base file at all, you can create your own!