header nav fix

assets/sass/_theme/_configuration.sass

@@ -93,15 +93,15 @@ $small-weight: normal !default
 
 // Signature
 $signature-font-family: $heading-font-family !default
-$signature-size-md: px2rem(22)
-$signature-size: px2rem(18)
+$signature-size-md: px2rem(22) !default
+$signature-size: px2rem(18) !default
 $signature-line-height: 130% !default
 $signature-weight: $heading-font-weight !default
 
 // Meta
 $meta-font-family: $heading-font-family !default
-$meta-size-md: px2rem(16)
-$meta-size: px2rem(14)
+$meta-size-md: px2rem(16) !default
+$meta-size: px2rem(14) !default
 $meta-line-height: 150% !default
 $meta-weight: $heading-font-weight !default
 
@@ -251,6 +251,7 @@ $block-call-to-action-button-color: $color-text !default
 // Block definitions
 $block-definition-border-color: $color-border !default
 $block-definition-border-color-hovered: $color-accent !default
+$block-definition-color-hovered: $color-accent !default
 $block-definition-font-size: $body-size !default
 $block-definition-font-size-md: $body-size-md !default
 

assets/sass/_theme/blocks/definitions.sass

@@ -10,7 +10,7 @@
             align-items: center
             transition: color 0.3s
             &:hover
-                color: $color-accent
+                color: $block-definition-color-hovered
         summary,
         p
             font-size: $block-definition-font-size

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

@@ -8,6 +8,18 @@ header[role="banner"]
     z-index: $zindex-header
     @include media-breakpoint-down(md)
         width: 100%
+    html.has-menu-opened &
+        &::after
+            background-color: $color-border
+            bottom: 0
+            content: ""
+            height: 1px
+            left: 0
+            position: absolute
+            -o-transition: background-color .4s
+            -moz-transition: background-color .4s
+            transition: background-color .4s
+            width: 100%
     .dropdown-menu
         transition: background $header-sticky-transition
     &.is-sticky, html.has-menu-opened &