diff --git a/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
index 9928ddd..850018a 100644
--- a/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -8,134 +8,93 @@
 /**
  * Implements hook_preprocess_HOOK() for maintenance-page.html.twig.
  */
-function seven_preprocess_maintenance_page(&$variables) {
+function seven_preprocess_maintenance_page(&$vars) {
   // While markup for normal pages is split into page.tpl.php and html.tpl.php,
   // the markup for the maintenance page is all in the single
   // maintenance-page.html.twig template. So, to have what's done in
   // seven_preprocess_html() also happen on the maintenance page, it has to be
   // called here.
-  seven_preprocess_html($variables);
+  seven_preprocess_html($vars);
 }
 
 /**
  * Implements hook_preprocess_HOOK() for html.tpl.php.
  */
-function seven_preprocess_html(&$variables) {
+function seven_preprocess_html(&$vars) {
   drupal_add_library('system', 'normalize');
+  // Add conditional CSS for IE8 and below.
+  drupal_add_css(path_to_theme() . '/ie.css', array('group' => CSS_AGGREGATE_THEME, 'browsers' => array('IE' => 'lte IE 8', '!IE' => FALSE), 'weight' => 999, 'preprocess' => FALSE));
 }
 
 /**
  * Implements hook_preprocess_HOOK() for page.tpl.php.
  */
-function seven_preprocess_page(&$variables) {
-  $variables['primary_local_tasks'] = $variables['tabs'];
-  unset($variables['primary_local_tasks']['#secondary']);
-  $variables['secondary_local_tasks'] = array(
+function seven_preprocess_page(&$vars) {
+  $vars['primary_local_tasks'] = $vars['tabs'];
+  unset($vars['primary_local_tasks']['#secondary']);
+  $vars['secondary_local_tasks'] = array(
     '#theme' => 'menu_local_tasks',
-    '#secondary' => isset($variables['tabs']['#secondary']) ? $variables['tabs']['#secondary'] : '',
+    '#secondary' => isset($vars['tabs']['#secondary']) ? $vars['tabs']['#secondary'] : '',
   );
 }
 
 /**
- * Displays the list of available node types for node creation.
+ * Implements hook_preprocess_HOOK() for node-add-list.html.twig.
  */
-function seven_node_add_list($variables) {
-  $content = $variables['content'];
-  $output = '';
-  if ($content) {
-    $output = '<ul class="admin-list">';
-    foreach ($content as $type) {
-      $output .= '<li class="clearfix">';
-      $content = '<span class="label">' . check_plain($type->name) . '</span>';
-      $content .= '<div class="description">' . filter_xss_admin($type->description) . '</div>';
-      $options['html'] = TRUE;
-      $output .= l($content, 'node/add/' . $type->type, $options);
-      $output .= '</li>';
+function seven_preprocess_node_add_list(&$variables) {
+  if (!empty($variables['content'])) {
+    foreach ($variables['content'] as $type) {
+      $variables['types'][$type->type]['label'] = check_plain($type->name);
+      $variables['types'][$type->type]['description'] = filter_xss_admin($type->description);
+      $variables['types'][$type->type]['path'] = url('node/add/' . $type->type);
     }
-    $output .= '</ul>';
   }
-  else {
-    $output = '<p>' . t('You have not created any content types yet. Go to the <a href="@create-content">content type creation page</a> to add a new content type.', array('@create-content' => url('admin/structure/types/add'))) . '</p>';
-  }
-  return $output;
 }
 
 /**
- * Overrides theme_custom_block_add_list().
+ * Implements hook_preprocess_HOOK() for custom-block-add-list.html.twig.
+ *
+ * Add variables for the label and the path separately.
+ *
+ * Displays the list of available custom block types for creation, adding
+ * separate variables for the label and the path.
  *
- * Displays the list of available custom block types for creation.
  */
-function seven_custom_block_add_list($variables) {
-  $content = $variables['content'];
-  $output = '';
-  if ($content) {
-    $output = '<ul class="admin-list">';
-    foreach ($content as $type) {
-      $output .= '<li class="clearfix">';
-      $content = '<span class="label">' . check_plain($type->label()) . '</span>';
-      $content .= '<div class="description">' . filter_xss_admin($type->description) . '</div>';
-      $options['html'] = TRUE;
-      $output .= l($content, 'block/add/' . $type->id(), $options);
-      $output .= '</li>';
+function seven_preprocess_custom_block_add_list(&$variables) {
+  if (!empty($variables['content'])) {
+    foreach ($variables['content'] as $type) {
+      $variables['types'][$type->id]['label'] = check_plain($type->label());
+      $variables['types'][$type->id]['description'] = filter_xss_admin($type->description);
+      $variables['types'][$type->id]['path'] = url('block/add/' . $type->id);
     }
-    $output .= '</ul>';
   }
-  return $output;
 }
 
 /**
- * Overrides theme_admin_block_content().
+ * Implements hook_preprocess_HOOK() for theme_admin_block_content().
  *
  * Uses an unordered list markup in both compact and extended mode.
  */
-function seven_admin_block_content($variables) {
-  $content = $variables['content'];
-  $output = '';
-  if (!empty($content)) {
-    $output = system_admin_compact_mode() ? '<ul class="admin-list compact">' : '<ul class="admin-list">';
-    foreach ($content as $item) {
-      $output .= '<li>';
-      $content = '<span class="label">' . filter_xss_admin($item['title']) . '</span>';
-      $options = $item['localized_options'];
-      $options['html'] = TRUE;
-      if (isset($item['description']) && !system_admin_compact_mode()) {
-        $content .= '<div class="description">' . filter_xss_admin($item['description']) . '</div>';
-      }
-      $output .= l($content, $item['href'], $options);
-      $output .= '</li>';
+function seven_preprocess_admin_block_content(&$variables) {
+  if (!empty($variables['content'])) {
+    $variables['compact'] = system_admin_compact_mode() ? 'compact' : '';
+    foreach ($variables['content'] as $key => $item) {
+      $variables['content'][$key]['label'] = filter_xss_admin($item['title']);
+      $variables['content'][$key]['path'] = url($item['href']);
+      $variables['content'][$key]['description'] = filter_xss_admin($item['description']);
     }
-    $output .= '</ul>';
   }
-  return $output;
 }
 
 /**
- * Overrides theme_tablesort_indicator().
+ * Implements hook_preprocess_HOOK() for tablesort-indicator.html.twig.
  *
  * Uses Seven's image versions, so the arrows show up as black and not gray on
  * gray.
  */
-function seven_tablesort_indicator($variables) {
-  $theme_path = drupal_get_path('theme', 'seven');
-
-  if($variables['style'] == 'asc') {
-    $image_uri = $theme_path . '/images/arrow-asc.png';
-    $text = t('Sort ascending');
-  }
-  else {
-    $image_uri = $theme_path . '/images/arrow-desc.png';
-    $text = t('Sort descending');
-  }
-
-  $image = array(
-    '#theme' => 'image',
-    '#uri' => $image_uri,
-    '#alt' => $text,
-    '#width' => 13,
-    '#height' => 13,
-    '#title' => $text,
-  );
-  return drupal_render($image);
+function seven_preprocess_tablesort_indicator(&$variables) {
+  $variables['uri'] = drupal_get_path('theme', 'seven') . '/images/arrow-' . ($variables['style'] == 'asc' ? 'asc' : 'desc') . '.png';
+  $variables['attributes']['src'] = file_create_url($variables['uri']);
 }
 
 /**
@@ -143,7 +102,6 @@ function seven_tablesort_indicator($variables) {
  */
 function seven_preprocess_install_page(&$variables) {
   drupal_add_js(drupal_get_path('theme', 'seven') . '/js/mobile.install.js');
-  drupal_add_css(drupal_get_path('theme', 'seven') . '/install-page.css', array('group' => CSS_AGGREGATE_THEME));
 }
 
 /**
@@ -156,7 +114,7 @@ function seven_form_node_form_alter(&$form, &$form_state) {
 
   $form['#theme'] = array('node_edit_form');
   $form['#attached'] = array(
-    'css' => array(drupal_get_path('module', 'node') . '/css/node.module.css'),
+    'css' => array(drupal_get_path('module', 'node') . '/node.edit.admin.css'),
   );
 
   $form['advanced']['#type'] = 'container';
diff --git a/core/themes/seven/templates/admin-block-content.html.twig b/core/themes/seven/templates/admin-block-content.html.twig
new file mode 100644
index 0000000..caed957
--- /dev/null
+++ b/core/themes/seven/templates/admin-block-content.html.twig
@@ -0,0 +1,26 @@
+{#
+/**
+ * @file
+ * Seven's theme implementation for the content of an administrative block.
+ *
+ * Available variables:
+ * - content: List of administrative menu items. Each menu item contains:
+ *   - path: Path to the admin section.
+ *   - label: Short name of the section.
+ *   - description: Description of the administrative menu item.
+ * - compact: Class indicator for compact mode (empty if not compact).
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_admin_block_content()
+ * @see seven_preprocess_custom_block_add_list()
+ *
+ * @ingroup themeable
+ */
+#}
+{% if content %}
+  <ul class="admin-list {{ compact }}">
+    {% for item in content %}
+      <li><a href="{{ item.path }}"><span class="label">{{ item.label }}</span><div class="description">{{ item.description }}</div></a></li>
+    {% endfor %}
+  </ul>
+{% endif %}
diff --git a/core/themes/seven/templates/custom-block-add-list.html.twig b/core/themes/seven/templates/custom-block-add-list.html.twig
new file mode 100644
index 0000000..ebd420d
--- /dev/null
+++ b/core/themes/seven/templates/custom-block-add-list.html.twig
@@ -0,0 +1,30 @@
+{#
+/**
+ * @file
+ * Overrides custom-block-add-list.html.twig.
+ *
+ * Displays the list of available custom block types for creation.
+ *
+ * Available variables:
+ * - types: A collection of all the available custom block types.
+ *   Each type contains:
+ *   - type: The custom block type, containing all the items below.
+ *   - link: A link to add a block of this type.
+ *   - description: A description of this custom block type.
+ *   - label: The title of the custom block type.
+ *   - path: A path for the link to add a block of this type.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_custom_block_add_list()
+ * @see seven_preprocess_custom_block_add_list()
+ *
+ * @ingroup themeable
+ */
+ #}
+<ul class="admin-list">
+  {% for type in types %}
+    <li class="clearfix">
+      <a href="{{ type.path }}"><span class="label">{{ type.label }}</span><div class="description">{{ type.description }}</div></a>
+    </li>
+  {% endfor %}
+</ul>
diff --git a/core/themes/seven/templates/node-add-list.html.twig b/core/themes/seven/templates/node-add-list.html.twig
new file mode 100644
index 0000000..bd79fe1
--- /dev/null
+++ b/core/themes/seven/templates/node-add-list.html.twig
@@ -0,0 +1,26 @@
+{#
+/**
+ * @file
+ * Seven's theme implementation to list node types available for adding content.
+ *
+ * Available variables:
+ * - types: List of content types. Each content type contains:
+ *   - add_link: Link to create a piece of content of this type.
+ *   - description: Description of this type of content.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_node_add_list()
+ * @see seven_preprocess_node_add_list()
+ *
+ * @ingroup themeable
+ */
+#}
+{% if content %}
+  <ul class="admin-list">
+    {% for type in types %}
+      <li class="clearfix"><a href="{{ type.path }}"><span class="label">{{ type.label }}</span><div class="description">{{ type.description }}</div></a></li>
+    {% endfor %}
+  </ul>
+{% else %}
+  <p>{{ 'You have not created any content types yet. Go to the <a href="@create-content">content type creation page</a> to add a new content type.'|t({'@create-content': url('admin/structure/types/add')}) }}</p>
+{% endif %}