& {
    #TabsToolbar {
        .tab-throbber {
            &[progress] {
                background-image: url("chrome://echelon/content/firefox-56/tabbrowser/loading.png");
            }
        }

        #tabs-newtab-button,
        #new-tab-button {
            .toolbarbutton-icon {
                @include set-background("firefox-56/tabbrowser/newtab.svg");
                fill: currentColor !important;
            }
        }

        .tab-background {
            &[selected] {
                .tab-background-middle {
                    background-image: url("chrome://echelon/content/firefox-29/tabbrowser/tab-active-middle.png"),
                    linear-gradient(transparent 2px, rgba(255,255,255,.4) 2px, rgba(255,255,255,.4)),
                                      none !important;
                }
    
                .tab-background-start,
                .tab-background-end {
                    &::before {
                        background-image: linear-gradient(transparent 2px, rgba(255,255,255,.4) 2px, rgba(255,255,255,.4)) !important;
                    }
                }
            }
        }
    }

    #tabbrowser-tabs[movingtab] > .tabbrowser-tab:last-of-type::after,
    .tabbrowser-tab:not([selected]):not(:hover + .tabbrowser-tab):not(:first-of-type):not(:first-of-type[selected] + .tabbrowser-tab):not(:hover)::before,
    #tabbrowser-tabs:not([overflow]) .tabbrowser-tab:not([selected]):last-of-type:not([beforehovered]):not(:hover)::after {
        width: 1px;
        margin-inline-start: -1px;
        margin-inline-end: 0;
        background-image: linear-gradient(transparent 5px,
                                          currentColor 5px,
                                          currentColor calc(100% - 4px),
                                          transparent calc(100% - 4px));
        opacity: 0.2;
        content: "";
        display: flex;
    }
    
}