userChrome.css for Firefox

userChrome.css

@-moz-document url(chrome://browser/content/browser.xhtml) {
	:root {
		--tab-min-height: 32px !important;
		--tab-border-radius: 0 !important;
		--tabs-navbar-shadow-size: 0 !important;
	}

	#main-window,
	browser[type="content-primary"],
	browser[type="content"],
	tabbrowser#content,
	#content,
	browser[type="content"] > html {
		background: #222 !important;
	}

	body,
	#navigator-toolbox,
	#titlebar {
		-moz-box-direction: reverse;
	}

	:root[tabsintitlebar][sizemode="maximized"] #titlebar {
		appearance: none !important;
	}

	#tabbrowser-tabs tab.tabbrowser-tab {
		padding-inline: unset !important;
	}

	#tabbrowser-tabs .tab-background {
		margin-block: unset !important;
		border-radius: 0 !important;
	}

	#urlbar[breakout][breakout-extend] {
		top: unset !important;
		bottom: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2);

		/* top: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2); */

		left: 0 !important;
		width: 100% !important;
	}

	#urlbar[breakout][breakout-extend],
	#urlbar[breakout][breakout-extend] > .urlbarView,
	#urlbar-results {
		display: flex !important;
		flex-direction: column-reverse;
	}

	#urlbar[breakout][breakout-extend] > #urlbar-input-container {
		height: var(--urlbar-height) !important;
		padding-block: 0 !important;
		padding-inline: 0 !important;
	}

	#urlbar[breakout][breakout-extend] > #urlbar-background {
		animation-name: none !important;
		box-shadow: 0 1px 4px rgba(0, 0, 0, .05) !important;
	}

	.urlbarView {
		margin-inline: 0 !important;
		width: 100% !important;
	}

	.urlbarView-row {
		padding-block: 0 !important;
	}

	.urlbarView-row-inner {
		padding-block: 4px !important;
	}

	.urlbarView-type-icon {
		min-width: 16px !important;
		height: 16px !important;
		margin-bottom: 0 !important;
		margin-inline-start: 0 !important;
	}

	.urlbarView-favicon {
		margin-inline-start: 20px !important;
	}
	#urlbar-input-container[pageproxystate="invalid"] #urlbar-go-button {
		display: block !important;
	}

	#urlbar[breakout][breakout-extend] hbox.search-one-offs {
		padding-block: 0 !important;
	}
}

userContent.css

@-moz-document url("about:newtab") {
  body {
    background-color: #222 !important;
  }
}

@-moz-document url("about:blank") {
  body {
    background-color: #222 !important;
  }
}