A bit of JS to improve the UX slightly... More tests. Everything is kosher now.

src/lib/components/Navigation.svelte

@@ -14,7 +14,14 @@
         <span class="mobile nav-header-logo">
             <Wordmark />
         </span>
-        <label for="nav-toggle" class="nav-toggle" aria-label="Toggle navigation">
+        <label
+            id="nav-toggle-label"
+            for="nav-toggle"
+            class="nav-toggle"
+            aria-controls="nav-menu"
+            aria-label="Toggle navigation"
+            aria-expanded="false"
+        >
             <span class="nav-toggle-inner">
                 <span class="nav-toggle-line"></span>
                 <span class="nav-toggle-line"></span>
@@ -22,7 +29,7 @@
             </span>
         </label>
     </div>
-    <div class="nav-menu container">
+    <div id="nav-menu" class="nav-menu container">
         <span class="nav-header-logo desktop">
             <Wordmark />
         </span>