(function(){
  const btn = document.querySelector('[data-menu-btn]');
  const menu = document.querySelector('[data-menu]');
  if(!btn || !menu) return;
  btn.addEventListener('click', function(){
    const isOpen = menu.classList.toggle('is-open');
    btn.setAttribute('aria-expanded', isOpen ? 'true' : 'false');
  });
})();
