Gadget framework provides the following files for each gadget for defining the user interface:

view.xhtml contains information about the user interface to be displayed when the gadget is rendered on the web page.

settings.xhtml contains information about the user interface for configuring the gadget at run time, if the gadget loading requires any runtime configuration.

view.xhtml and settings.xhtml files of each gadget are individually bootstrap enabled by default. This means that the gadgets are already within a bootstrap container, and the use of Grid System within a gadget is sufficient to make the layout responsive. If you are using AngularJS version of the gadget, you can also use the AngularUI Bootstrap library that are already included as part of the application.