Firefox 89.0beta Skeuomorph tabs

userChrome.css

.tab-background {
	border-radius: var(--tab-border-radius) var(--tab-border-radius) 0px 0px !important;
	margin-bottom: 0px !important;
}

#tabbrowser-tabs:not([movingtab]) > #tabbrowser-arrowscrollbox > .tabbrowser-tab > .tab-stack > .tab-background[multiselected="true"]:-moz-lwtheme, #tabbrowser-tabs:not([movingtab]) > #tabbrowser-arrowscrollbox > .tabbrowser-tab > .tab-stack > .tab-background[selected="true"]:-moz-lwtheme {
	background-image: linear-gradient(var(--toolbar-bgcolor, transparent), var(--toolbar-bgcolor, transparent)), linear-gradient(var(--toolbar-bgcolor), var(--toolbar-bgcolor)), var(--lwt-header-image, none) !important;
}

#TabsToolbar[brighttext] #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected="true"], [multiselected]) > .tab-stack > .tab-background:-moz-lwtheme {
	box-shadow: 0 0 1px var(--dark-menu-color) !important;
}

.tab-content {
	margin-top: var(--proton-tab-block-margin);
}

#TabsToolbar .toolbarbutton-1 {
	margin-top: var(--proton-tab-block-margin) !important;
}

@Dragoner7
I can't find --dark-menu-color. Do you mean --toolbar-color?

@black7375 When using Remote Debugging to inspect the browser UI, Firefox prompted it as an option, when typing var(--something). I don't know where it's being defined thought. It's not in browser.css.

you can find css vars:

// at Remote Debugging Webconsole
getComputedStyle(document.documentElement).getPropertyValue('--css-var-name')

@Dragoner7
I used this code at my project, what about the license?
I'am currently write a list of credits.

@black7375 Yeah, I know, I use your theme, It's really good. 😄

MPL 2.0, I guess? Since it contains some snippets from the Firefox source.

Ok, good.
Thank you for using my project.