grav-admin-first/user/plugins/admin/themes/grav/scss/template/_tabs.scss

$tab-label-height: 50px;

// New JS powered tabs
.form-tabs {

    .admin-pages &:first-child {
        margin-top: -1rem;
    }
    .admin-pages & {
        .tabs-nav {
            margin-right: 180px;

            @include breakpoint(mobile-only) {
                margin-right: 0 !important;
            }
        }
    }

    .tabs-nav {
        @include display(flex);
        padding-top: 1px;

        a {
            @include flex(1);
            transition: color 0.5s ease, background 0.5s ease;
            cursor: pointer;
            min-height: $tab-label-height;
            text-align:center;

            padding: 4px;

            display: flex;
            align-items: center;
            justify-content: center;

        }

        span {
            display: inline-block;
            line-height: 1.1;
        }


    }

    &.subtle .tabs-nav {
        margin-right: 0 !important;
    }

    .tabs-content {

        .tab__content {
            display: none;
            padding-top: 2rem;

            &.active {
                display: block;
            }
        }
    }

    &.side-tabs {
        display: flex;
        background: none;

        > .tabs-nav {
            width: 20%;
            display: block;
            padding-top: 1.5rem;

            a {
                text-align: left;
                flex: none;
                justify-content: left;
                padding-left: 15px;
            }
        }

        > .tabs-content {
            width: 80%;
        }
    }
}


// Old tabs here for posterity!
//.tab-bar {
//    @include clearfix;
//    margin: 0;
//    padding: 0;
//    list-style: none;
//
//    li {
//
//        display: block;
//        float: left;
//        height: $tab-label-height;
//
//        @include breakpoint(mobile-only) {
//            width: 100%;
//            span, a {
//                width: 100%;
//                text-align: center;
//            }
//        }
//    }
//
//    span, a {
//        @extend .default-animation;
//        display: inline-block;
//        padding: 0 4rem;
//        line-height: $tab-label-height;
//    }
//}