css-backend.scss

@import 'app';
#app {
    $authorized: true;

    &.middlewares {
        .succeeds {
            // Middleware passed!
        }

        .fails {
            @include view("Unauthorized");
        }
    }

    &.router {
        &.homepage {
            &::before {
                AuthenticationMiddleware();
            }

            @include view("welcome");
        }
    }
}

@function AuthenticationMiddleware() {
    @return $authorized === true;
}

@mixin view($str) {
    content: $str;
}