Replace zen grids with css grid. Move print styles print style file. Remove Drupal specific styles.

sass/components/box/_box.scss

@@ -2,7 +2,7 @@
 //
 // A simple box style.
 //
-// A Drupal block is often styled as a box. However, this design component is
+// A block is often styled as a box. However, this design component is
 // not applied to any blocks by default; it is used as an example of how to
 // build and document a CSS component.
 //
@@ -35,19 +35,9 @@
   }
 
   // Sass compiles this nested ruleset's selector into:
-  // .box:focus, .box:hover, .box.is-focus, .box--is-focus,
-  // %box:focus, %box:hover, %box.is-focus, %box--is-focus {}
-  //
-  // The ".box--is-focus" class is a stray class we don't actually want, but we
-  // deal with it because we often want a placeholder selector like
-  // %box--is-focus in case we need to use @extends later.
-  //
-  // The ".is-" part of the class name is a Drupal 8 BEM naming convention that
-  // indicates the "focus" is a _state_ of the "box" component.
+  // .box:focus, .box:hover, %box:focus, %box:hover
   &:focus,
-  &:hover,
-  &.is-focus,
-  &--is-focus {
+  &:hover {
     border-color: color(text);
   }
 
@@ -59,28 +49,3 @@
     border-color: color(link);
   }
 }
-
-//
-// Drupal selectors.
-//
-// In this part of the file, we write some fugly selectors if we can't figure
-// out how to insert the class we want (.box) into the Drupal theme system. Then
-// we @extend from the fugly selector into the nicely-written component
-// selector.
-//
-
-// You could create a theme hook suggestion and override the block.tpl.php just
-// for the sidebar regions or write a HOOK_preprocess_block() function to check
-// for the regions and insert the classes into the right variables, or, if you
-// have no idea what I'm talking about, you could just use this fugly CSS
-// selector:
-//
-// [class$="sidebar"] {
-//   .block {
-//     @extend %box;
-//   }
-//
-//   .block__title {
-//     @extend %box__title;
-//   }
-// }

sass/components/hidden/_hidden.scss

@@ -24,15 +24,3 @@
     @extend %hidden;
   }
 }
-
-//
-// Drupal selectors.
-//
-
-.element-hidden {
-  @extend %js-hidden;
-}
-
-.js-hide {
-  @extend %js-hidden;
-}

sass/components/hidden/hidden.twig

@@ -1,3 +0,0 @@
-<div class="hidden {{modifier_class}}">
-  This content is hidden.
-</div>

sass/components/highlight-mark/_highlight-mark.scss

@@ -14,12 +14,3 @@
   // Remove background highlighting from <mark> in normalize.
   background-color: transparent;
 }
-
-//
-// Drupal selectors. (In case a module doesn't use theme_mark().)
-//
-
-.new,
-.update {
-  @extend %highlight-mark;
-}

sass/components/inline-links/_inline-links.scss

@@ -22,15 +22,3 @@
     }
   }
 }
-
-//
-// Drupal selectors.
-//
-
-.inline.links {
-  @extend %inline-links;
-
-  li {
-    @extend %inline-links__item;
-  }
-}

sass/components/inline-sibling/_inline-sibling.scss

@@ -31,25 +31,3 @@
     display: inline;
   }
 }
-
-//
-// Drupal selectors.
-//
-
-// Drupal core.
-.field-label-inline {
-  .field-label {
-    @extend %inline-sibling;
-  }
-
-  // Revert core's ridiculous styling without polluting the component.
-  .field-label,
-  .field-items {
-    float: none;
-  }
-}
-
-// The inline field label used by the Fences 7.x-1.x module.
-span.field-label {
-  @extend %inline-sibling;
-}

sass/components/print-none/_print-none.scss

@@ -16,17 +16,3 @@
     display: none;
   }
 }
-
-//
-// Drupal selectors.
-//
-
-// Hide Drupal nav elements.
-.toolbar,
-.action-links,
-.links,
-.book-navigation,
-.forum-topic-navigation,
-.feed-icons {
-  @extend %print-none;
-}

sass/components/responsive-video/_responsive-video.scss

@@ -34,12 +34,3 @@
     padding-bottom: (3/4)*100%; // 4:3 aspect ratio
   }
 }
-
-//
-// Drupal selectors.
-//
-
-.media-youtube-video,
-.media-vimeo-preview-wrapper {
-  @extend %responsive-video;
-}

sass/components/visually-hidden/_visually-hidden.scss

@@ -26,16 +26,3 @@
     }
   }
 }
-
-//
-// Drupal selectors.
-//
-
-.element-invisible {
-  @extend %visually-hidden;
-}
-
-.element-focusable {
-  @extend %visually-hidden;
-  @extend %visually-hidden--focusable;
-}

sass/components/wireframe/_wireframe.scss

@@ -20,14 +20,20 @@ $with-wireframes: false !default;
   }
 
   //
-  // Drupal selectors.
+  // Zen selectors.
   //
 
-  .header,
-  .layout-3col > div,
-  .footer,
-  .region-bottom {
-    @extend %wireframe;
+  .layout {
+    &__header,
+    &__footer,
+    &__content,
+    &__navigation,
+    &__first-sidebar,
+    &__second-sidebar,
+    &__page-top,
+    &__page-bottom {
+      @extend %wireframe;
+    }
   }
 
 }