string, any valid CSS color name, or hex color code. Only
works for "full_screen" method.</p></dd>


<dt><code>footer</code></dt>
<dd><p>Additional Shiny/HTML component to add below the loader, like
a title <code>h1("load title")</code>. <code>inline</code> method does not have a footer.</p></dd>


<dt><code>z_index</code></dt>
<dd><p>number, only works for "full_screen" method, what CSS layer
should the overlay be places. In HTML, all elements have the default of 0.</p></dd>


<dt><code>alert</code></dt>
<