Do you really need a new block for this?  It seems like you could instead just override the body block:

```
{% block body %}
<div class="overlay" style="display:none;">
  <div class="fullscreen-wrapper">
    ...
  </div>
</div>
{% endblock body %}
```

In fact, since you aren't using any of the "normal" page content (nav bar, content div, etc), you should probably be extending `skel.html` instead -- that template has a completely empty `body` block, which you can extend.

I haven't looked closely at the css but I'm guessing this means you wouldn't need the "overlay" stuff.