Admin login can't find css

Silverstripe Version: 4.1

The login screen doesn’t load any CSS and I’m getting an error thrown in SSViewer::construct:

**None of the following templates could be found: Array ( [0] =>Array ( [type] =>Includes [0] => Header ) [1] => Header ) in themes "Array ( [0] => $public [1] => $default ) "**

I have a theme.yml file from the Lessons site:

---
Name: mytheme
---
SilverStripe\View\SSViewer:
  themes:
- '$public'
- '$default'

The files it can’t find are reset, typography, form and layout.

I downloaded the zip of 4.1 and installed it through the installer, I haven’t done anything with composer. When I look through the files I don’t see any css, I do see scss in /vendor/silverstripe/admin/client/src/styles.

There’s a code comment in _forms.scss

... base styles defined in framework/css/Form.css

I don’t see any css directory in /vendor/silverstripe/framework

EDIT: yes I have been ?flushing…
I don’t have a themes directory at all as per the Lessons instructions.

This things a mystery… It’s decided to stop throwing the error now.

Now I have an un-styled login form. The template used to render it is

/vendor/silverstripe/cms/templates/BlankPage.ss

Which unsurprisingly is… a blank page.

Here’s what I see. “Chosen” there is the value of $this->chosen in SSViewer::__construct

SilverStripe does ship with a branded CMS login right? It’s not that it’s considered part of our projects and we have to lay it up?

The login page itself is unstyled, it takes it’s styling from your theme, usually. If there’s no theme (yet), it’ll fall back to a blank page.

Sonofa… that is super weird.

Thanks for filling me in @Firesphere