Trying to add CSS styles to a theme This is the content of the .info.yml file.

name: Endymion
description: Drupal 8 starter theme
type: theme
core: 8.x

libraries:
    - endymion/global-css

regions:
  header: Header
  primary_menu: 'Primary menu'
  breadcrumb: Breadcrumb
  content: Content
  sidebar_first: 'Sidebar first'
  footer_first: 'Footer first'


This is the content of the .libraries.yml file.

global-css:
    css:
        theme:
            css/css1.css: {}


I keep getting this error message:


  The website encountered an unexpected error. Please try again later.


How do I fix this error?

Additional point:

Get the same error message whether I'm running locally or on a remote server (siteground)
AFAIK you should use 2 spaces to indent your YAML. It seems you either use 4 spaces or a tab. 

That is the case for the libraries files as well as the libraries key in info file.