Update

Author: accgit

src/css/style.menu.css

@@ -14,8 +14,14 @@
           padding: 7px 8px;
 }
 
-.nav .responsive { display: none; }
-.nav .expand-responsive { display: block !important; }
+.nav .responsive {
+    transition: opacity 0.2s ease-in-out;
+       opacity: 0;
+}
+
+.nav .expandable {
+    opacity: 1;
+}
 
 /*
     sidebar
@@ -119,8 +125,8 @@
 	height: 800px;
     }
 
-    .nav .click { display: none; }
-    .nav .responsive { display: block; }
+    .nav .click { opacity: 0; }
+    .nav .responsive { opacity: 1; }
 
     .sidebar {
 	position: fixed;

src/index.html

@@ -115,17 +115,13 @@
 
 			// responsive sidebar
 			$('.nav .click').on('click', function() {
-				var nav = '.nav .responsive';
-				$(nav).slideToggle('fast');
-				$(window).on('resize', function() {
-					$(window).width() >= 768 ? $(nav).show() : $(nav).hide();
-				});
+				$('.nav .responsive').toggleClass('expandable');
 			});
 
 			// click submenu
 			$('ul.menu li').each(function() {
 				if ($(this).children('li.parent a.current').length > 0 ) {
-					$(this).parent().find('ul.submenu').css('display', 'block');
+					$(this).parent().find('ul.submenu').toggle();
 					$(this).parent().find('li.parent').addClass('active');
 				}
 			});