3 hrs found just some css that really matter to me.

gtk.css

@define-color colorPrimary #fff;

gtk-widgets.css

/*******
* CSD *
******/

.titlebar {
background-image: linear-gradient(to bottom,
shade (@colorPrimary, 0.95),
shade (@colorPrimary, 0.95)
);
border-color: shade (@colorPrimary, 0.56);
border-radius: 4px 4px 0 0;
border-style: solid;
border-width: 0 0 1px;

text-shadow: 0 1px alpha (shade (@colorPrimary, 1.4), 0.40);
icon-shadow: 0 1px alpha (shade (@colorPrimary, 1.4), 0.40);

box-shadow: inset 0 0 0 1px alpha (shade (@colorPrimary, 1.4), 0.20),
inset 0 1px 0 0 alpha (shade (@colorPrimary, 1.4), 0.60);

padding: 0 3px;
}

.titlebar:backdrop {
background-image: linear-gradient(to bottom,
shade (@colorPrimary, 0.96),
shade (@colorPrimary, 0.96)
);
background-color: shade (@colorPrimary, 1.10);
border-color: shade (@colorPrimary, 0.64);

box-shadow: inset 0 0 0 1px alpha (shade (@colorPrimary, 1.4), 0.40);

-gtk-image-effect: dim;
}