userChrome.css

:root {
	--bg: #000000;
	--bg-alt: #1F1F1F;
	--fg: #BFBFBF;
	--fg-alt: #575757;
	--toolbar-field-focus-border-color: #0000 !important;
	--lwt-tab-text: var(--fg) !important;
}

.titlebar-spacer,
#tracking-protection-icon-container,
#urlbar-zoom-button,
#pageActionButton,
#page-action-buttons,
#urlbar-go-button,
#alltabs-button,
#identity-box,
#statuspanel,
#home-button,
#downloads-button,
toolbarspring {
	display: none !important;
}

/* urlbar */

#nav-bar {
    border: none !important;
    box-shadow: none !important;
    height: 45px !important;
    background-color: var(--bg) !important;
}

#navigator-toolbox {
    border: 0px !important;
}

#TabsToolbar {
    height: 45px !important;
	 margin-top: 3px !important;
	 margin-bottom: -3px !important;
    background-color: var(--bg) !important;
}

#urlbar .urlbarView {
	display: none !important;
}

#urlbar[breakout][breakout-extend]{
  display: block !important;
  position: absolute !important;
  width: 100% !important;
  height: var(--urlbar-height) !important;
  top: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2) !important;
  left: 0 !important;
}

#urlbar-input {
	color: var(--fg) !important;
}

#urlbar-input-container {
	padding: 0px 7px !important;
	height: 100% !important;
}

#urlbar-background {
    border: transparent !important;
    animation: none !important;
    box-shadow: none !important;
	background-color: var(--bg-alt) !important;
}

.urlbarView-row[selectable][selected] > .urlbarView-row-inner, .urlbarView-row-inner[selectable][selected] {
	background-color: var(--bg-alt) !important;
}

#urlbar,
#tabbrowser-tabs:not([noshadowfortests]) .tab-background:is([selected], [multiselected]) {
	box-shadow: none !important;
}

/* tabs */

.tabbrowser-tab[selected] .tab-background {
	background: var(--bg-alt) !important;
}

tab:not([selected]) .tab-label {
	color: var(--fg-alt) !important;
}

#tabs-newtab-button {
	fill: var(--fg-alt) !important;
}

#tabs-newtab-button:hover {
	fill: var(--fg) !important;
}

.tabbrowser-tab:not(:hover) .tab-close-button { 
	display: none !important; 
}

.tabbrowser-tab:not([pinned]):hover .tab-close-button { 
	display: block !important; 
}

scrollbox, .scrollbox-clip {
	padding-left: 2px !important;
}

#tabbrowser-tabs[haspinnedtabs]:not([positionpinnedtabs]) > #tabbrowser-arrowscrollbox > .tabbrowser-tab[first-visible-unpinned-tab] {
	margin-inline-start: 0px !important;
}

.tabbrowser-tab[fadein] {
	max-width: 100vw !important 
}

/* misc */

.header-container,
.body-container,
.footer-container,
findbar {
	background-color: var(--bg) !important;
	color: var(--fg) !important;
}