By default, new CSS files created in the Code Editor automatically include ‘modules.css’. What does ‘modules.css’ do?
It ensures that the layout is responsive — without it, nothing will be responsive.
It ensures that fixed-width modules, such as images or forms, become responsive.
It creates styling for modules that only applies to desktop devices.
It adds a ‘View Desktop Site’ link at the bottom of each page.
https://www.youtube.com/watch?v=r6FiLwLFDyQ