=== modified file 'Ambiance/gtk-3.0/gtk-main.css'
--- Ambiance/gtk-3.0/gtk-main.css	2014-03-07 19:14:18 +0000
+++ Ambiance/gtk-3.0/gtk-main.css	2014-06-18 12:29:13 +0000
@@ -35,6 +35,8 @@
 @define-color backdrop_selected_bg_color shade (@bg_color, 0.92);
 @define-color backdrop_selected_fg_color @fg_color;
 
+@define-color shadow_color alpha(black, 0.5);
+
 @import url("gtk-widgets-borders.css");
 @import url("gtk-widgets-assets.css");
 @import url("gtk-widgets.css");

=== modified file 'Ambiance/gtk-3.0/gtk-widgets.css'
--- Ambiance/gtk-3.0/gtk-widgets.css	2014-03-27 18:20:38 +0000
+++ Ambiance/gtk-3.0/gtk-widgets.css	2014-06-18 12:29:13 +0000
@@ -71,19 +71,19 @@
     outline-offset: 5px;
 }
 
-GtkWindow {
+.background {
     color: @fg_color;
     background-color: @bg_color;
 }
 
+.background:backdrop {
+    color: @backdrop_fg_color;
+}
+
 GtkPaned {
     background-color: @bg_color;
 }
 
-GtkWindow:backdrop {
-    color: @backdrop_fg_color;
-}
-
 GtkEventBox {
     background-color: @bg_color;
 }
@@ -2237,6 +2237,24 @@
     border-width: 0;
 }
 
+/************
+ * popover  *
+ ************/
+.popover {
+    background-clip: border-box;
+
+    border-radius: 5px;
+    border: 1px solid darker(@bg_color);
+
+    box-shadow: 0 2px 3px @shadow_color;
+    margin: 10px;
+    padding: 2px;
+}
+
+.popover:backdrop {
+    box-shadow: none;
+}
+
 /*****************************************************************************
  * states [please keep this section at the end of the file (CSS precedence)] *
  *****************************************************************************/

=== modified file 'Radiance/gtk-3.0/gtk-main.css'
--- Radiance/gtk-3.0/gtk-main.css	2014-03-07 19:14:18 +0000
+++ Radiance/gtk-3.0/gtk-main.css	2014-06-18 12:29:13 +0000
@@ -34,6 +34,8 @@
 @define-color backdrop_selected_bg_color shade (@bg_color, 0.92);
 @define-color backdrop_selected_fg_color @fg_color;
 
+@define-color shadow_color alpha(black, 0.5);
+
 @import url("gtk-widgets-borders.css");
 @import url("gtk-widgets-borders-radiance.css");
 @import url("gtk-widgets-assets.css");

=== modified file 'Radiance/gtk-3.0/gtk-widgets.css'
--- Radiance/gtk-3.0/gtk-widgets.css	2014-03-27 18:20:38 +0000
+++ Radiance/gtk-3.0/gtk-widgets.css	2014-06-18 12:29:13 +0000
@@ -70,19 +70,19 @@
     outline-offset: 5px;
 }
 
-GtkWindow {
+.background {
     color: @fg_color;
     background-color: @bg_color;
 }
 
+.background:backdrop {
+    color: @backdrop_fg_color;
+}
+
 GtkPaned {
     background-color: @bg_color;
 }
 
-GtkWindow:backdrop {
-    color: @backdrop_fg_color;
-}
-
 GtkEventBox {
     background-color: @bg_color;
 }
@@ -2250,6 +2250,24 @@
 }
 
 
+/************
+ * popover  *
+ ************/
+.popover {
+    background-clip: border-box;
+
+    border-radius: 5px;
+    border: 1px solid darker(@bg_color);
+
+    box-shadow: 0 2px 3px @shadow_color;
+    margin: 10px;
+    padding: 2px;
+}
+
+.popover:backdrop {
+    box-shadow: none;
+}
+
 /*****************************************************************************
  * states [please keep this section at the end of the file (CSS precedence)] *
  *****************************************************************************/