Help with widget background color

Hi, I hate to make a topic out of this but I’ve been wracking my brain. I’m trying to customize a widget’s background while playing with textualize. If I take the custom widget showcased in the readme that turns red when you hover over it and want the background color not to leave the borders, how might I do that?

Will seems to accomplish what I want in a video at the 10:40 mark. I totally understand that he’s working on the CSS branch and that this is a separate concept, but is it not possible to do it on the main branch by setting the borders to a particular value? Perhaps by setting a the style attribute?

I am by no means proficient in CSS and I hoped I wouldn’t have to wait for that branch to be merged to accomplish what I want. Also if there is a better place for this kind of quick question please let me know.