diff --git a/app/models/stylesheet.rb b/app/models/stylesheet.rb
index e1f258b0f..193b37581 100644
--- a/app/models/stylesheet.rb
+++ b/app/models/stylesheet.rb
@@ -1,3 +1,8 @@
+# frozen_string_literal: true
+
+# Stylesheet is a cached CSS file that allows to easily customize the interface of Fab-Manager with some configurable colors and
+# a picture for the background of the user's profile.
+# There's only one stylesheet record in the database, which is updated on each colour change.
 class Stylesheet < ActiveRecord::Base
   validates_presence_of :contents
 
@@ -45,43 +50,45 @@ class Stylesheet < ActiveRecord::Base
     Stylesheet.primary.paint.to_rgb.insert(3, 'a').insert(-2, ", #{alpha}")
   end
 
-  def self.css
-    ".bg-red { background-color: #{Stylesheet.primary}; }
-     .bg-red-dark { background-color: #{Stylesheet.primary}; }
-     #nav .nav { background-color: #{Stylesheet.primary}; }
-     #nav .nav > li > a { color: white; }
-     #nav .nav > li > a:hover, #nav .nav > li > a:focus { background-color: #{Stylesheet.primary_light}; }
-     #nav .nav > li > a.active { border-left: 3px solid #{Stylesheet.primary_dark}; background-color: #{Stylesheet.primary_light}; }
-     #nav .nav > li > a.active { border-left: 3px solid #{Stylesheet.primary_dark}; background-color: #{Stylesheet.primary_light}; }
-     .btn-theme { background-color: #{Stylesheet.primary}; color: white; }
-     .btn-theme:active, .btn-theme:hover { background-color: #{Stylesheet.primary_dark}; }
-     .label-theme { background-color: #{Stylesheet.primary} }
-     .btn-link { color: #{Stylesheet.primary} !important; }
-     .btn-link:hover { color: #{Stylesheet.primary_dark} !important; }
-     a { color: #{Stylesheet.primary}; }
-     a:hover, a:focus { color: #{Stylesheet.primary_dark}; }
-     h2, h3, h5 { color: #{Stylesheet.primary}; }
-     h5:after { background-color: #{Stylesheet.primary}; }
-     .bg-yellow { background-color: #{Stylesheet.secondary} !important; }
-     .event:hover { background-color: #{Stylesheet.primary}; }
-     .widget h3 { color: #{Stylesheet.primary}; }
-     .modal-header h1, .custom-invoice .modal-header h1 { color: #{Stylesheet.primary}; }
-     .block-link:hover, .fc-toolbar .fc-button:hover, .fc-toolbar .fc-button:active, .fc-toolbar .fc-button.fc-state-active { background-color: #{Stylesheet.secondary}; }
-     .carousel-control:hover, .carousel-control:focus, .carousel-caption .title a:hover { color: #{Stylesheet.secondary}; }
-     .well.well-warning { border-color: #{Stylesheet.secondary};  background-color: #{Stylesheet.secondary};  }
-     .text-yellow { color: #{Stylesheet.secondary} !important; }
-     .red { color: #{Stylesheet.primary} !important; }
-     .btn-warning, .editable-buttons button[type=submit].btn-primary { background-color: #{Stylesheet.secondary} !important; border-color: #{Stylesheet.secondary} !important; }
-     .btn-warning:hover, .editable-buttons button[type=submit].btn-primary:hover, .btn-warning:focus, .editable-buttons button[type=submit].btn-primary:focus, .btn-warning.focus, .editable-buttons button.focus[type=submit].btn-primary, .btn-warning:active, .editable-buttons button[type=submit].btn-primary:active, .btn-warning.active, .editable-buttons button.active[type=submit].btn-primary, .open > .btn-warning.dropdown-toggle, .editable-buttons .open > button.dropdown-toggle[type=submit].btn-primary { background-color: #{Stylesheet.secondary_dark} !important; border-color: #{Stylesheet.secondary_dark} !important; }
-     .btn-warning-full { border-color: #{Stylesheet.secondary}; background-color: #{Stylesheet.secondary}; }
-     .heading .heading-btn a:hover { background-color: #{Stylesheet.secondary}; }
-     .pricing-panel .content .wrap { border-color: #{Stylesheet.secondary}; }
-     .pricing-panel .cta-button .btn:hover, .pricing-panel .cta-button .custom-invoice .modal-body .elements li:hover, .custom-invoice .modal-body .elements .pricing-panel .cta-button li:hover { background-color: #{Stylesheet.secondary} !important; }
-     a.label:hover, .form-control.form-control-ui-select .select2-choices a.select2-search-choice:hover, a.label:focus, .form-control.form-control-ui-select .select2-choices a.select2-search-choice:focus { color: #{Stylesheet.primary}; }
-     .about-picture { background: linear-gradient( rgba(255,255,255,0.12), rgba(255,255,255,0.13) ), linear-gradient( #{Stylesheet.primary_with_alpha(0.78)}, #{Stylesheet.primary_with_alpha(0.82)} ), url('/about-fablab.jpg') no-repeat; }
-     .social-icons > div:hover { background-color: #{Stylesheet.secondary}; }
-     .profile-top { background: linear-gradient( rgba(255,255,255,0.12), rgba(255,255,255,0.13) ), linear-gradient(#{Stylesheet.primary_with_alpha(0.78)}, #{Stylesheet.primary_with_alpha(0.82)} ), url('#{CustomAsset.get_url('profile-image-file') || '/about-fablab.jpg'}') no-repeat; }
-     .profile-top .social-links a:hover { background-color: #{Stylesheet.secondary} !important; border-color: #{Stylesheet.secondary} !important; }
-     section#cookies-modal div.cookies-consent .cookies-actions button.accept { background-color: #{Stylesheet.secondary}; }"
+  def self.css # rubocop:disable Metrics/AbcSize
+    <<~CSS
+      .bg-red { background-color: #{Stylesheet.primary}; }
+      .bg-red-dark { background-color: #{Stylesheet.primary}; }
+      #nav .nav { background-color: #{Stylesheet.primary}; }
+      #nav .nav > li > a { color: white; }
+      #nav .nav > li > a:hover, #nav .nav > li > a:focus { background-color: #{Stylesheet.primary_light}; }
+      #nav .nav > li > a.active { border-left: 3px solid #{Stylesheet.primary_dark}; background-color: #{Stylesheet.primary_light}; }
+      #nav .nav > li > a.active { border-left: 3px solid #{Stylesheet.primary_dark}; background-color: #{Stylesheet.primary_light}; }
+      .btn-theme { background-color: #{Stylesheet.primary}; color: white; }
+      .btn-theme:active, .btn-theme:hover { background-color: #{Stylesheet.primary_dark}; }
+      .label-theme { background-color: #{Stylesheet.primary} }
+      .btn-link { color: #{Stylesheet.primary} !important; }
+      .btn-link:hover { color: #{Stylesheet.primary_dark} !important; }
+      a { color: #{Stylesheet.primary}; }
+      a:hover, a:focus { color: #{Stylesheet.primary_dark}; }
+      h2, h3, h5 { color: #{Stylesheet.primary}; }
+      h5:after { background-color: #{Stylesheet.primary}; }
+      .bg-yellow { background-color: #{Stylesheet.secondary} !important; }
+      .event:hover { background-color: #{Stylesheet.primary}; }
+      .widget h3 { color: #{Stylesheet.primary}; }
+      .modal-header h1, .custom-invoice .modal-header h1 { color: #{Stylesheet.primary}; }
+      .block-link:hover, .fc-toolbar .fc-button:hover, .fc-toolbar .fc-button:active, .fc-toolbar .fc-button.fc-state-active { background-color: #{Stylesheet.secondary}; }
+      .carousel-control:hover, .carousel-control:focus, .carousel-caption .title a:hover { color: #{Stylesheet.secondary}; }
+      .well.well-warning { border-color: #{Stylesheet.secondary};  background-color: #{Stylesheet.secondary};  }
+      .text-yellow { color: #{Stylesheet.secondary} !important; }
+      .red { color: #{Stylesheet.primary} !important; }
+      .btn-warning, .editable-buttons button[type=submit].btn-primary { background-color: #{Stylesheet.secondary} !important; border-color: #{Stylesheet.secondary} !important; }
+      .btn-warning:hover, .editable-buttons button[type=submit].btn-primary:hover, .btn-warning:focus, .editable-buttons button[type=submit].btn-primary:focus, .btn-warning.focus, .editable-buttons button.focus[type=submit].btn-primary, .btn-warning:active, .editable-buttons button[type=submit].btn-primary:active, .btn-warning.active, .editable-buttons button.active[type=submit].btn-primary, .open > .btn-warning.dropdown-toggle, .editable-buttons .open > button.dropdown-toggle[type=submit].btn-primary { background-color: #{Stylesheet.secondary_dark} !important; border-color: #{Stylesheet.secondary_dark} !important; }
+      .btn-warning-full { border-color: #{Stylesheet.secondary}; background-color: #{Stylesheet.secondary}; }
+      .heading .heading-btn a:hover { background-color: #{Stylesheet.secondary}; }
+      .pricing-panel .content .wrap { border-color: #{Stylesheet.secondary}; }
+      .pricing-panel .cta-button .btn:hover, .pricing-panel .cta-button .custom-invoice .modal-body .elements li:hover, .custom-invoice .modal-body .elements .pricing-panel .cta-button li:hover { background-color: #{Stylesheet.secondary} !important; }
+      a.label:hover, .form-control.form-control-ui-select .select2-choices a.select2-search-choice:hover, a.label:focus, .form-control.form-control-ui-select .select2-choices a.select2-search-choice:focus { color: #{Stylesheet.primary}; }
+      .about-picture { background: linear-gradient( rgba(255,255,255,0.12), rgba(255,255,255,0.13) ), linear-gradient( #{Stylesheet.primary_with_alpha(0.78)}, #{Stylesheet.primary_with_alpha(0.82)} ), url('/about-fablab.jpg') no-repeat; }
+      .social-icons > div:hover { background-color: #{Stylesheet.secondary}; }
+      .profile-top { background: linear-gradient( rgba(255,255,255,0.12), rgba(255,255,255,0.13) ), linear-gradient(#{Stylesheet.primary_with_alpha(0.78)}, #{Stylesheet.primary_with_alpha(0.82)} ), url('#{CustomAsset.get_url('profile-image-file') || '/about-fablab.jpg'}') no-repeat; }
+      .profile-top .social-links a:hover { background-color: #{Stylesheet.secondary} !important; border-color: #{Stylesheet.secondary} !important; }
+      section#cookies-modal div.cookies-consent .cookies-actions button.accept { background-color: #{Stylesheet.secondary}; }
+    CSS
   end
 end