This theme provides a near native look when used with the basic (non DWM) titlebars.
This is NOT a theme that should be used with the normal DWM titlebars, and instead should be used with DWM disabled or with a program that makes the basic frames render such as BasicThemer2. This theme only works as intended at 100% scale, but I'm currently in the process of adding support for 125% scale (titlebar buttons are blurry, when maximized the restore button disappears).
If your screen size is a size other than 1080p, go into the CSS file and change the numbers for the lines starting with @media. They are in rems (to avoid Firefox interface scaling), so you'll have to multiply your screen size in pixels by 0.0625 to get the size in rems.
In addition, you might also have to make the titlebars of windows slightly smaller if you're using the default titlebar size, as otherwise you might see the real buttons display on top of the fake ones implemented by this theme.
To install this, open about:support, open the profile folder, and copy the chrome folder into the profile folder.
If the theme doesn't apply, go to about:config and set toolkit.legacyUserProfileCustomizations.stylesheets to true.
