fenix-fox/chrome/autohide_toolbox.css

/* Hide the whole toolbar area unless urlbar is focused or cursor is over the toolbar */
/* Dimensions on non-Win10 OS probably needs to be adjusted */

@media (-moz-os-version: windows-win10){

  :root[sizemode="maximized"]:not([inDOMFullscreen]){ margin-top: 10px !important; }
  :root[sizemode="maximized"] #navigator-toolbox{ margin-top: -2px }

  @media screen and (min-resolution: 1.25dppx){
    :root[sizemode="maximized"]:not([inDOMFullscreen]){ margin-top: 9px !important; }
  }
  @media screen and (min-resolution: 1.5dppx){
    :root[sizemode="maximized"]:not([inDOMFullscreen]){ margin-top: 8px !important; }
    :root[sizemode="maximized"] #navigator-toolbox{ margin-top: -1px }
  }
  @media screen and (min-resolution: 2dppx){
    :root[sizemode="maximized"]:not([inDOMFullscreen]){ margin-top: 7px !important; }
  }
}

:root[sizemode="fullscreen"]{ margin-top: 0px !important; }

#navigator-toolbox{
  position: fixed !important;
  display: block;
  background-color: var(--lwt-accent-color,black) !important;
  transition: transform 82ms 33ms linear, opacity 82ms 33ms linear !important;
  transform-origin: top;
  line-height: 0;
  z-index: 1;
}

#navigator-toolbox > *{ line-height: normal }

#navigator-toolbox,
#navigator-toolbox > *{
  width: 100vw;
  -moz-appearance: none !important;
}

#navigator-toolbox:not(:focus-within):not(:hover){
  transform: rotateX(86deg);
  opacity: 0;
}

:root[sizemode="maximized"] #navigator-toolbox:not(:focus-within):not(:hover){ transform: rotateX(89.5deg) }

/* Don't apply transform before window has been fully created */
:root:not([sessionrestored]) #navigator-toolbox{ transform:none !important }

:root[customizing] #navigator-toolbox{
  position: relative !important;
  transform: none !important;
  opacity: 1 !important;
}

#navigator-toolbox[inFullscreen] > #PersonalToolbar,
#PersonalToolbar[collapsed="true"]{ display: none }

/* Uncomment this if tabs toolbar is hidden with hide_tabs_toolbar.css */
 /*#titlebar{ margin-bottom: -9px }*/