//Dropdown lists
document.getElementById('dropdown').addEventListener('change', function() {
  var selectedOption = this.value;
  var allContents = document.querySelectorAll('.content');
  for (var i = 0; i < allContents.length; i++) {
    if (allContents[i].id === selectedOption) {
      allContents[i].classList.remove('hidden');
    } else {
      allContents[i].classList.add('hidden');
    }
  }
});