diff -u /dev/null b/core/themes/bartik/bartik.libraries.yml
--- /dev/null
+++ b/core/themes/bartik/bartik.libraries.yml
@@ -0,0 +1,54 @@
+base:
+  version: VERSION
+  css:
+    theme:
+      # Base
+      css/base/elements.css: {}
+      css/base/typography.css: {}
+      # Components
+      css/components/admin.css: {}
+      css/components/book.css: {}
+      css/components/breadcrumb.css: {}
+      css/components/captions.css: {}
+      css/components/colors.css: {}
+      css/components/comments.css: {}
+      css/components/content.css: {}
+      css/components/dropbutton.css: {}
+      css/components/featured.css: {}
+      css/components/footer.css: {}
+      css/components/form.css: {}
+      css/components/hacks.css: {}
+      css/components/header.css: {}
+      css/components/help.css: {}
+      css/components/highlighted.css: {}
+      css/components/list.css: {}
+      css/components/messages.css: {}
+      css/components/node-preview.css: {}
+      css/components/pager.css: {}
+      css/components/primary-menu.css: {}
+      css/components/search.css: {}
+      css/components/search-results.css: {}
+      css/components/secondary-menu.css: {}
+      css/components/shortcut.css: {}
+      css/components/skip-link.css: {}
+      css/components/sidebar.css: {}
+      css/components/table.css: {}
+      css/components/tabs.css: {}
+      css/components/tips.css: {}
+      css/components/triptych.css: {}
+      css/components/user.css: {}
+      css/components/views.css: {}
+      # Layout
+      css/layout/layout.css: {}
+      # Print
+      css/print.css: { media: print }
+      css/components/buttons.css: {}
+      css/components/media.css: {}
+maintenance_page:
+  version: VERSION
+  css:
+    theme:
+      css/theme/maintenance-page.css: {}
+  dependencies:
+    - system/maintenance
+    - bartik/base