Stylus doesn't seem to activate the theme, even though it should match the url. I've tried other stylish editor themes as well, but since they were built for Chrome I wasn't sure what URL it filters extensions on firefox. This, however, seems to have support, but it doesn't work regardless :/

Any ideas?

For now, package.json and stylus-dark.user.css have different versions.

If you're okay with this, I could make a pull request.

Can you add the ability to customize the background colors? I have no issues doing it myself but it would be nice to be able to have UserCSS options so that I can update without losing my customization. Below are the classes that I've edited the color (they're all background colors):

/*ADDED CODE*/

#header, body, input[type=checkbox]:not(.slider), .firefox select, input:not(.slider), .newUI .entry, .CodeMirror, .CodeMirror-gutters{
    background: #333333 !important;
}

For

regexp("chrome-extension://.*"),
regexp("moz-extension://.*")

can be replaced by:

url-prefix("chrome-extension://"),
url-prefix("moz-extension://")

Or:

regexp("(?:chrome|moz)-extension:\/\/.+")

I'm not sure why this is, but if I install this as a UserCSS through Stylus in Firefox 65.0, it styles portions of various websites. I tried editing the regexp to be specific to my Stylus extension, but then it just fails to style anything. I'm not sure why this is happening. Could this be caused by using ShadowFox?

Fixed on my extension, attached the edited version.

`/* Fixing backup buttons background w/wo hover */

#backup-buttons .dropdown-content {
background-color: #0e0e0e;
}
#backup-buttons .dropdown-content a:hover {
background-color: #201e1e;
}`

Default style of Stylish seems to treat select differently, so #header select doesn’t simply inherit from #header. Simply

select {
    color: silver;
}

works.

When opening the options in Stylus with this userstyle enabled, only these items have this userstyle's dark theme applied:

• Color pickers (e.g. pickers beside "Background color" and "Background color when disabled")
• Number pickers (e.g. picker beside "Popup width (in pixels)")
• Buttons (e.g. buttons like "Reset options" and "Back to manage")

The background for the action menu of a style in the popup is unstyled.

From the pop up window (when clicking on the stylus icon) the result 'cards' in Find Styles are hard to read, it would be nice to have :

.search-result {
    background: #353b48!important;
}

or equivalent.