text: const hamburgerBtnRef = document.querySelector('.hamburger');
  const headerNavigationRef = document.querySelector('.header-navigation');
  const heroRef = document.querySelector('.hero');
  
  hamburgerBtnRef.addEventListener('click', onToggleBurger);
  headerNavigationRef.addEventListener('click', onClickNav);
  
  function onToggleBurger() {
    hamburgerBtnRef.classList.toggle('is-active');
  
    if (hamburgerBtnRef.classList.contains('is-active')) {
      headerNavigationRef.classList.add('is-open');
      heroRef.addEventListener('click', onHeroClick);
    } else {
      headerNavigationRef.classList.remove('is-open');
      heroRef.removeEventListener('click', onHeroClick);
    }
  }
  
  function onCloseMenu() {
    hamburgerBtnRef.classList.remove('is-active');
    headerNavigationRef.classList.remove('is-open');
  }
  
  function onClickNav(e) {
    if (e.target !== headerNavigationRef) {
      onCloseMenu();
      heroRef.removeEventListener('click', onHeroClick);
    }
  }
  
  function onHeroClick() {
    onCloseMenu();
    heroRef.removeEventListener('click', onHeroClick);
  }
  