Show unrated puzzles different, dark theme adjustments

src/css/states/puzzle_menu.scss

@@ -26,6 +26,10 @@
             @include S(border-radius, $globalBorderRadius);
             flex-wrap: wrap;
 
+            @include DarkThemeOverride {
+                background: $accentColorDark;
+            }
+
             input.search {
                 color: #333;
                 margin: 0;
@@ -60,6 +64,10 @@
                 @include PlainText;
                 @include S(margin-right, 10px);
 
+                @include DarkThemeOverride {
+                    color: #bbbbc4;
+                }
+
                 input {
                     @include S(width, 15px);
                     @include S(height, 15px);
@@ -311,6 +319,9 @@
                             &.stage--hard {
                                 color: $colorRedBright;
                             }
+                            &.stage--unknown {
+                                color: #888;
+                            }
                         }
                     }