styling a popup

Hi, 

I have a popup that I want to create when clicking on the "Register" link on the login dropdown form.  I was able to use the info at http://learn.elgg.org/en/2.3/guides/javascript.html#module-elgg-popup to create my popup, but now I'm trying to style it.  Below is the code i have in the core /engine/lib/navigation.php (I do plan to override, but for some reason I couldn't get it to work just yet so I plan to do it once I can get the core function working):

function _elgg_login_menu_setup($hook, $type, $return, $params) {
        if (elgg_get_config('allow_registration')) {
        echo elgg_format_element('div', [
                'class' => 'elgg-module-popup hidden',
                'id' => 'popup-module',
        ], '<a href="https://mycustomurl" target="_blank">Get the Pen app</a>');
                $return[] = \ElggMenuItem::factory(array(
                        'name' => 'register',
                        'text' => elgg_echo('register'),
                        'rel' => 'popup',
                        'href' => '#popup-module',
                        'link_class' => 'registration_link',
                ));
        }
        $return[] = \ElggMenuItem::factory(array(
                'name' => 'forgotpassword',
                'href' => 'forgotpassword',
                'text' => elgg_echo('user:password:lost'),
                'link_class' => 'forgot_link',
        ));
        return $return;
}

Then, I updated /view/default/elements/modules.css.php:

/* Popup */
.elgg-module-popup {
        background-color: black;
        border: 1px solid #ccc;
        z-index: 9999;
        margin-bottom: 0;
        padding: 5px;
        border-radius: 6px;
        box-shadow: 4px 4px 4px rgba(0, 0, 0, 0.5);
        width: 300px;
        height: 200px;
}

saved, flushed the cache, but nothing in my popup changes.

Beginning Developers

Beginning Developers

This space is for newcomers, who wish to build a new plugin or to customize an existing one to their liking