Adwaita: simpler gtkcalendar style (once again)

gtk/resources/theme/Adwaita/_common.scss

@@ -2602,37 +2602,39 @@ GtkScrolledWindow {
 GtkCalendar {
   color: $text_color;
   border: 1px solid $borders_color;
+
   &:selected {
     background-color: $selected_bg_color;
     color: $selected_fg_color;
     border-radius: 3px;
-    &:backdrop {
-      color: if($variant=='light', $backdrop_base_color, $backdrop_fg_color);
-    }
+
+    &:backdrop { color: if($variant=='light', $backdrop_base_color, $backdrop_fg_color); }
   }
+
   &.header {
-    @extend .titlebar;
-    color: $fg_color;
-    box-shadow: inset 0 -1px mix($borders_color, $bg_color, 30%),
-                inset 0px 1px $top_hilight,
-                0 1px 2px transparentize(black,0.9);
-    border: 1px solid $borders_color;
+    border: 1px solid transparentize(black, 0.9);
     border-radius: 0;
-    &:backdrop {
-      color: $backdrop_fg_color;
-      box-shadow: none;
-    }
+
+    &:backdrop { border-color: transparentize(black, 0.9); }
   }
+
   &.button {
     @extend %undecorated_button;
     color: transparentize($fg_color, 0.55);
+
     &:hover {
       @extend %undecorated_button;
       color: $fg_color;
     }
-    &:backdrop { color: transparentize($backdrop_fg_color,0.55); }
+
+    &:backdrop {
+      @extend %undecorated_button;
+      color: transparentize($backdrop_fg_color,0.55);
+    }
   }
+
   &.highlight, &.highlight:backdrop { color: gtkalpha(currentColor, 0.55); }
+
   &:backdrop {
     color: $backdrop_text_color;
     border-color: $backdrop_borders_color;