My Firefox CSS

userChrome.css

#TabsToolbar > * {
	visibility: collapse;
}

#titlebar{ margin-bottom: -22px}

/* hide navigation bar when it is not focused; use Ctrl+L to get focus */
#main-window:not([customizing]) #navigator-toolbox:not(:focus-within):not(:hover) {
	margin-top: -105px;			/**/
}
#navigator-toolbox {
  transition: 1s margin-top ease-out;
}

#nav-bar ~ #PersonalToolbar:not([customizing]) {
  position: fixed !important;
  padding: 3px 2px 2px !important;
  height: auto !important;
  border-top: 0px solid transparent!important;
  border-right: 1px solid transparent !important;
  border-bottom: 1px solid rgba(0,0,0,0.3) !important;
  border-left: 1px solid transparent !important;
  box-shadow: 0 0px 2px rgba(0,0,0,0);
  width: 100%;
  transform: translateY(-100%);
  transition: transform 1s !important;
  opacity: 0;
}

#navigator-toolbox:hover >
#nav-bar ~ #PersonalToolbar:not([customizing]) {
  transform: translateY(0);
  opacity: 1;
}

#toolbar-menubar:not([inactive="true"]) ~
#nav-bar ~ #PersonalToolbar:not([customizing]) {
  transform: translateY(0);
  opacity: 1;
}

:root[uidensity=compact] #navigator-toolbox {
  --nav-bar-height: 33px;
  --bookmark-bar-height: 23px;
  --navbar-transition-time: 0.1s;
}

:root:not([uidensity]) #navigator-toolbox {
  --nav-bar-height: 39px;
  --bookmark-bar-height: 23px;
  --navbar-transition-time: 0.1s;
}

:root[uidensity=touch] #navigator-toolbox {
  --nav-bar-height: 41px;
  --bookmark-bar-height: 25px;
  --navbar-transition-time: 0.1s;
}

:root:not([customizing]) #nav-bar, #PersonalToolbar {
  z-index: 1;
  display: block !important;
  position: fixed !important;
  min-height: 0 !important;
  height: 0 !important;
  width: 100%;
  opacity: 0;
  transition: opacity var(--navbar-transition-time) ease-in, height var(--navbar-transition-time) linear !important;
  pointer-events: none;
}

:root:not([customizing]) #nav-bar
{
  transition-delay: var(--navbar-transition-time) !important;
  z-index: 10;
}

:root:not([customizing]) #navigator-toolbox:hover #nav-bar,
:root:not([customizing]) #navigator-toolbox:focus-within #nav-bar {
  transition-delay: 0s !important;
  height: var(--nav-bar-height) !important;
  opacity: 1;
  pointer-events: all;
}

/* If the bookmarks bar is turned on, auto-hide that too */
:root:not([customizing]) #PersonalToolbar {
  margin-top: var(--nav-bar-height) !important;
}

:root:not([customizing]) #navigator-toolbox:hover #PersonalToolbar,
:root:not([customizing]) #navigator-toolbox:focus-within #PersonalToolbar {
  transition-delay: var(--navbar-transition-time) !important;
  height: var(--bookmark-bar-height) !important;
  opacity: 1;
  pointer-events: all;
}

/* haxx for the menu button */
:root:not([customizing]) #nav-bar #nav-bar-customization-target {
  width: calc(100% - 35px);
}

:root:not([customizing]) #PanelUI-button {
  top: -9px;
  position: relative;
}

/* Lightweight Theme Support */
:root:-moz-lwtheme #nav-bar,
:root:-moz-lwtheme #PersonalToolbar {
  background-color: var(--lwt-accent-color) !important;
  background-image: var(--lwt-header-image), var(--lwt-additional-images) !important;
  background-position: var(--lwt-background-alignment) !important;
  background-repeat: var(--lwt-background-tiling) !important;
}