The script itself does not take care of any styling whatsoever, not even the
display property. It basically mostly toggles the
aria-hidden attribute on the dialog itself and its counterpart content containers (where the rest of the site/app lives).
Here is a solid set of styles to get started (note that you might have to rename the class names to fit your code):
The rest, such as what the dialog really looks like, and how its content is styled, is left at your own discretion. These styles should be enough to get you on the right track. Feel free to look at the demo for more extensive styles.