bartik subtheme and css I want to make some modifications to the bartik theme i am using D8
(like changing the logo position,etc) i created a subtheme
named it "mytheme" 
following the instruction i found here:

https://www.drupal.org/docs/8/theming-drupal-8/creating-a-drupal-8-sub-theme-or-sub-theme-of-sub-theme

So, first I created the mytheme.info.yml file containing:

name: mytheme
type: theme
base theme: bartik
description: subtheme for bartik
core: 8.x
libraries:
  mytheme/global-styling
regions:
  header: Header
  primary_menu: 'Primary menu'
  secondary_menu: 'Secondary menu'
  page_top: 'Page top'
  page_bottom: 'Page bottom'
  highlighted: Highlighted
  featured_top: 'Featured top'
  breadcrumb: Breadcrumb
  content: Content
  sidebar_first: 'Sidebar first'
  sidebar_second: 'Sidebar second'
  featured_bottom_first: 'Featured bottom first'
  featured_bottom_second: 'Featured bottom second'
  featured_bottom_third: 'Featured bottom third'
  footer_first: 'Footer first'
  footer_second: 'Footer second'
  footer_third: 'Footer third'
  footer_fourth: 'Footer fourth'
  footer_fifth: 'Footer fifth'


Next i created the mytheme.libraries.yml containing the following:

global-styling:
  css:
    theme:
      css/style.css: {}


i went to appearance and enabled "mytheme" as default, went back to site, looks identical to how bartik was
so far so good

my problem now is, how do i move on with the customizations i want to do?

i created a folder called: "css" in "mytheme" directory, inside the css folder i created a blank file called "style.css" and 
there i wrote the first modification i want to do

.region-header .site-branding {
    float: none;
    text-align: center;
}


When i go back to site i see no difference, the logo remains on the left like it was on bartik

Can somebody help please?

I am not sure how to proceed and if what I did by creating a css folder, etc is the right way.

Thank you.
Not sure if this is still relevant or not but I was having the same issue and I was just missing a dash.


  libraries: 
    mytheme/global-styling


to


  libraries: 
    - mytheme/global-styling