Firefox-UI-Fix/src/utils/_window_control.scss

@use "os" as *;

@mixin WindowControl_Right() {
  @include OS($win) {
    @content;
  }
  @include OS($linux) {
    @media (-moz-gtk-csd-reversed-placement: 0) {
      @content;
    }
  }
}

@mixin WindowControl_Left() {
  @include OS($mac) {
    @content;
  }
  @include OS($linux) {
    @media (-moz-gtk-csd-reversed-placement) {
      @content;
    }
  }
}