How to fill the empty space created by margin, with background colour?

[Everything2067]

My bar currently looks like this. I would like to fill the dark background so that the space created by the margin is completely filled, like this (edited)

config.jsonc: https://gist.github.com/Everything2067/2f7d0994645774586a024c5cb420d5be
style.css: https://gist.github.com/Everything2067/bb90237271bab7a97bdd4afab20e3f43

I am using niri.

[Everything2067]

Fixed it by removing the margin line in config.jsonc and adding the following to style.css:

window#waybar > box {
    margin: 5px;
}