@media (max-width: 768px) {
  #menu-check ~ label .close-icon {
    display: none;
  }

  #menu-check ~ label .open-icon {
    display: inline-block;
  }

  #menu-check:checked ~ label .close-icon {
    display: inline-block;
  }

  #menu-check:checked ~ label .open-icon {
    display: none;
  }

  #menu-check:checked ~ #menu {
    display: block;
  }
}