How To Put All Butons/menu Square Corner Not Rounded.

how to put all butons/menu square corner not rounded?

i'm using the brightness style/theme, and i want to make all the butons/menu items etc/ in square.

At first, check Theme editor

did that from theme, it made only cart button square not entire theme.

So additional changes are required to add square corners to other elements. Use CSS section of the Theme editor to do it

maybe help