Add server-side rendering (via bundleRenderer, as this is what the Vue docs recommend, and apparently the only way it does encapsulation)

templates/VueSpa/ClientApp/components/navmenu/navmenu.css

@@ -0,0 +1,66 @@
+.main-nav li .glyphicon {
+    margin-right: 10px;
+}
+
+/* Highlighting rules for nav menu items */
+.main-nav li a.router-link-active,
+.main-nav li a.router-link-active:hover,
+.main-nav li a.router-link-active:focus {
+    background-color: #4189C7;
+    color: white;
+}
+
+/* Keep the nav menu independent of scrolling and on top of other items */
+.main-nav {
+    position: fixed;
+    top: 0;
+    left: 0;
+    right: 0;
+    z-index: 1;
+}
+
+@media (max-width: 767px) {
+    /* On small screens, the nav menu spans the full width of the screen. Leave a space for it. */
+    body {
+        padding-top: 50px;
+    }
+}
+
+@media (min-width: 768px) {
+    /* On small screens, convert the nav menu to a vertical sidebar */
+    .main-nav {
+        height: 100%;
+        width: calc(25% - 20px);
+    }
+    .main-nav .navbar {
+        border-radius: 0px;
+        border-width: 0px;
+        height: 100%;
+    }
+    .main-nav .navbar-header {
+        float: none;
+    }
+    .main-nav .navbar-collapse {
+        border-top: 1px solid #444;
+        padding: 0px;
+    }
+    .main-nav .navbar ul {
+        float: none;
+    }
+    .main-nav .navbar li {
+        float: none;
+        font-size: 15px;
+        margin: 6px;
+    }
+    .main-nav .navbar li a {
+        padding: 10px 16px;
+        border-radius: 4px;
+    }
+    .main-nav .navbar a {
+        /* If a menu item's text is too long, truncate it */
+        width: 100%;
+        white-space: nowrap;
+        overflow: hidden;
+        text-overflow: ellipsis;
+    }
+}

templates/VueSpa/ClientApp/components/navmenu/navmenu.vue.html

@@ -33,3 +33,5 @@
         </div>
     </div>
 </template>
+
+<style src="./navmenu.css" />