fixed search button fixed for mobile

assets/sass/_theme/design-system/search.sass

@@ -148,7 +148,7 @@
                 padding-top: calc(#{$spacing3} + #{half($spacing0)})
 
 .pagefind-fixed
-    background: $color-background
+    background: $color-background-alt
     bottom: 0
     left: $spacing3
     min-width: calc(#{$spacing3} * 3)
@@ -161,6 +161,8 @@
         left: 0
         width: 100vw
         &.in-page-with-toc
+            background: $color-background
+            border-top: 1px solid #eee
             bottom: px2rem(44)
 
 .pagefind-footer