var menuBtn = $('.menu-btn');
var nav = $('nav');
var lineOne = $('.menu-btn .line--1');
var lineTwo = $('.menu-btn .line--2');
var lineThree = $('.menu-btn .line--3');
var link = $('nav .nav-links');

menuBtn.click(function(event) {
    nav.toggleClass('nav-open');
    lineOne.toggleClass('line-cross');
    lineTwo.toggleClass('line-fade-out');
    lineThree.toggleClass('line-cross');
    link.toggleClass('fade-in');
});