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How to make Make sidebar menu full width when screen width is mobile

How can I make a responsive page like the example below.
ezgif.com-gif-maker

In this example I want to make the menu group on left side full page width when page width is similar to mobile. (<500 pxs)

I am able to hide the elements based on page width, but need a way to set the width of the menu group equal to page width when page width is like mobile.