#TabsToolbar[brighttext]
  #tabbrowser-tabs:not([noshadowfortests])
  .tabbrowser-tab[visuallyselected="true"]:not(:focus)
  > .tab-stack
  > .tab-background:-moz-lwtheme {
  /* Origina: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9))
       Bright: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
  box-shadow: 0 0 1px var(--toolbar-color) !important;
}
#TabsToolbar[brighttext]
  #tabbrowser-tabs:not([noshadowfortests])
  .tabbrowser-tab[multiselected]:not([visuallyselected])
  > .tab-stack
  > .tab-background:-moz-lwtheme {
  box-shadow: 0 0 1px color-mix(in srgb, var(--toolbar-color) 80%, transparent) !important;
}

/* Consider 0 0 4px rgba(128,128,142,0.9) -> 0 0 4px rgba(0,0,0,.4) new default */
#TabsToolbar:not([brighttext])
  #tabbrowser-tabs:not([noshadowfortests])
  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
  > .tab-stack
  > .tab-background {
  box-shadow: 0 0 1px var(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9))),
    0 0 4px rgba(128, 128, 142, 0.5) !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(--tab-line-color, var(--lwt-tab-line-color, rgba(128, 128, 142, 0.9))) !important;
}

/* For themes outside of Light and Dark (which are curated by Mozilla), show a thicker border
   around the tab to help themes that are dependent on tab_line to show the selected tab. */
:root:not([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(240, 240, 244); --lwt-text-color: rgba(21, 20, 26);"])
  #TabsToolbar:not([brighttext])
  #tabbrowser-tabs:not([noshadowfortests])
  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
  > .tab-stack
  > .tab-background:-moz-lwtheme {
  box-shadow: 0 0 0 1px
      var(--tab-line-color, var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)))),
    0 0 4px rgba(128, 128, 142, 0.5) !important;
}

:root:not([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
  #TabsToolbar[brighttext]
  #tabbrowser-tabs:not([noshadowfortests])
  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
  > .tab-stack
  > .tab-background:-moz-lwtheme {
  box-shadow: 0 0 0 1px
    var(--tab-line-color, var(--lwt-tab-line-color, var(--tabs-border-color, rgba(128, 128, 142, 0.9)))) !important;
}