Change UI based off of screen size

I am creating a bullet curtain game for PC and Mobile. I have this idea to do two different types of UI, but maintain the same game throughout. I want to do something similar to what the images show below (From Jigoku Kisetsukan: Sense of the Seasons). I have been searching for answers but haven't found much to do with varying screen sizes unless you are wanting to scale everything. I only want to scale the main game screen, and they have my external UI to be wide if they have a wide screen, or a condensed version if they are on a portrait view.

PC:

Mobile: