Take a look at the syntax, you used linear-gradient(--building-color1, --window-color1) inside linear-gradient. Is this the correct way to reference variables in CSS? Please check the background above to see how it references the color variable
I’ve edited your code for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.
You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.