Making shapes with only CSS

Hi there! I’ll get to the point.
My issue is with this exercise: https://learn.freecodecamp.org/responsive-web-design/applied-visual-design/create-a-graphic-using-css/
I understand what they did, but I was wondering if there was a way I could do exactly this without using the style tags (customise the shape entirely with CSS instead).
Thank you!

The div was styled “entirely with css”. You may link a css file in the document <head> instead. Linking to a file didn’t make sense in the lesson environment, but is the usual way of connecting to css.

hello! sorry i haven’t been on here for a while. i figured it out, i wasn’t using “background-color”, so the shape wasn’t showing up. thanks tho!