tissue/resources/assets/sass/_underline-tabs.scss

.tis-nav-underline-tabs {
    margin-bottom: -1px;

    .nav-link {
        padding: 0.5rem 1.25rem;
        border-bottom: 4px solid transparent;

        @include media-breakpoint-up(lg) {
            padding: 1rem 1.25rem;
        }

        &.active {
            border-bottom-color: $primary;
        }
    }
}