Change the color of the hamburger on focus instead of outlining.

It's prettier, and it does the job of indicating where the focus is.
We need a secondary color, to complement the blue, though.

user/themes/textbook/css/custom.css

@@ -94,22 +94,6 @@ iframe.geogebra {
     border: 1px dotted #a6a6a6;
 }
 
-/** Fix Mobile Navigation -- OLD **/
-
-/*.mobile-container ul.treemenu-root li span.toggler {*/
-/*    line-height: 2.22rem;*/
-/*    font-size: 2.22rem;*/
-/*    padding: 0.92rem 0.1rem;*/
-/*    margin: 0;*/
-/*}*/
-
-/*.mobile-container ul.treemenu-root li a {*/
-/*    line-height: 2.22rem;*/
-/*    font-size: 2.22rem;*/
-/*    padding: 0.92rem 1.618rem;*/
-/*    margin: 0;*/
-/*}*/
-
 /** Desktop header navigation *****************************************************************************************/
 
 /*nav.dropmenu > ul > li > ul > li {*/
@@ -169,8 +153,13 @@ iframe.geogebra {
     opacity: 0;
 }
 
-#mobile-navigation-toggle:focus ~ .mobile-menu .button_container {
-    outline: 1px dotted darkcyan;
+/*#mobile-navigation-toggle:focus ~ .mobile-menu .button_container {*/
+/*    outline: 1px dotted darkcyan;*/
+/*}*/
+#mobile-navigation-toggle:focus ~ .mobile-menu .button_container .top,
+#mobile-navigation-toggle:focus ~ .mobile-menu .button_container .middle,
+#mobile-navigation-toggle:focus ~ .mobile-menu .button_container .bottom {
+    background-color: #262d84;
 }
 
 #mobile-navigation-toggle:checked {