Update mobile menu headings

src/components/navigation/menu-item/menu-item.scss

@@ -94,24 +94,44 @@
       }
 
       &.is-heading {
-        @include font-size(24px, 24px);
+        @include font-size(24px, 28px);
         @include font-weight($bold);
-        background: transparent;
-        border-bottom: 3px solid var(--brand-main-light);
-        color: var(--brand-main-light);
-        margin-top: -24px;
-        padding-bottom: 24px;
-        padding-top: 24px;
+        letter-spacing: -0.06px;
         text-transform: uppercase;
+        position: relative;
+
+        // Drill-down heading.
+        &:not(.is-active):not(.is-active-trail) {
+          color: var(--brand-main-light);
+          margin-top: 8px;
+          padding-bottom: 12px;
+          padding-right: 8px;
+          padding-top: 12px;
+
+          &:before {
+            background-color: var(--brand-main-light);
+            content: '';
+            display: block;
+            height: 3px;
+            left: 0;
+            position: absolute;
+            right: 0;
+            top: -8px;
+          }
+        }
 
         &.is-active,
         &.in-active-trail {
           @include font-weight($bold);
+          background: transparent;
+          border-bottom: 0;
           color: var(--grayscale-black);
-          position: relative;
+          margin-top: -12px;
+          padding-bottom: 24px;
+          padding-top: 24px;
 
           &:before {
-            border-left-width: 4px;
+            border-left-width: 5px;
             height: 55%;
           }
         }