document.addEventListener("DOMContentLoaded", function (event) {

   /*
    * Display the menu items on smaller screens
    */
    var pull = document.getElementById('pull');
    var menu = document.querySelector('nav ul');

    pull.addEventListener('click', function (e) {
        menu.classList.toggle('hide');
    });

   /*
    * Make the header images move on scroll
    */
    window.addEventListener('scroll', function () {
        var x = window.pageYOffset || document.body.scrollTop;
        var main = document.getElementById("main");
        var mainStyle = main.style;
        
        mainStyle.backgroundPosition = '100% ' + parseInt(-x/3) + 'px' + ', 0%, center top';
    });
});