diff --git a/core/modules/node/css/node.admin.css b/core/modules/node/css/node.admin.css
index 101a38d..a5a0667 100644
--- a/core/modules/node/css/node.admin.css
+++ b/core/modules/node/css/node.admin.css
@@ -4,8 +4,101 @@
  */
 
 /**
+ * Node add/edit form layout
+ */
+
+/* Narrow screens */
+.layout-region {
+  box-sizing: border-box;
+}
+
+/* Wide screens */
+@media
+  screen and (min-width: 780px),
+  (orientation: landscape) and (min-device-height: 780px) {
+
+  .layout-region-node-main,
+  .layout-region-node-footer {
+    float: left; /* LTR */
+    width: 65%;
+    padding-right: 2em; /* LTR */
+  }
+
+  [dir="rtl"] .layout-region-node-main,
+  [dir="rtl"] .layout-region-node-footer {
+    float: right;
+    padding-left: 2em;
+    padding-right: 0;
+  }
+
+  .layout-region-node-secondary {
+    float: right; /* LTR */
+    width: 35%;
+  }
+
+  [dir="rtl"] .layout-region-node-secondary {
+    float: left;
+  }
+
+  /* @todo File an issue to add a standard class to all text-like inputs */
+  .layout-region-node-secondary .form-autocomplete,
+  .layout-region-node-secondary .form-text,
+  .layout-region-node-secondary .form-tel,
+  .layout-region-node-secondary .form-email,
+  .layout-region-node-secondary .form-url,
+  .layout-region-node-secondary .form-search,
+  .layout-region-node-secondary .form-number,
+  .layout-region-node-secondary .form-color,
+  .layout-region-node-secondary textarea {
+    box-sizing:         border-box;
+    width: 100%;
+    max-width: 100%;
+  }
+}
+
+/**
+ * The vertical toolbar mode gets triggered for narrow screens, which throws off
+ * the intent of media queries written for the viewport width. When the vertical
+ * toolbar is on, we need to suppress layout for the original media width + the
+ * toolbar width (240px). In this case, 240px + 780px.
+ */
+@media
+  screen and (max-width: 1020px) {
+
+  .toolbar-vertical.toolbar-tray-open .layout-region-node-main,
+  .toolbar-vertical.toolbar-tray-open .layout-region-node-footer,
+  .toolbar-vertical.toolbar-tray-open .layout-region-node-secondary {
+    float: none;
+    width: auto;
+    padding-right: 0;
+  }
+}
+
+
+/**
  * Revisions overview screen.
  */
 .revision-current {
   background: #ffc;
 }
+
+/**
+ * Styles for node preview page.
+ */
+
+.node-preview-container {
+  position: fixed;
+  z-index: 499;
+  width: 100%;
+  padding: 10px;
+}
+
+@media only screen and (min-width: 36em) {
+  .node-preview-container .form-type-select {
+    margin-left: 25%; /* LTR */
+  }
+  [dir="rtl"] .node-preview-container .form-type-select {
+    margin-right: 25%;
+    margin-left: 0%;
+  }
+}
diff --git a/core/modules/node/css/node.preview.css b/core/modules/node/css/node.preview.css
deleted file mode 100644
index 481a02e..0000000
--- a/core/modules/node/css/node.preview.css
+++ /dev/null
@@ -1,21 +0,0 @@
-/**
- * @file
- * Styles for node preview page.
- */
-
-.node-preview-container {
-  position: fixed;
-  z-index: 499;
-  width: 100%;
-  padding: 10px;
-}
-
-@media only screen and (min-width: 36em) {
-  .node-preview-container .form-type-select {
-    margin-left: 25%; /* LTR */
-  }
-  [dir="rtl"] .node-preview-container .form-type-select {
-    margin-right: 25%;
-    margin-left: 0%;
-  }
-}