@media (max-width: 680px) {
  .nav.open {
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 8px 18px 12px;
    border-bottom: 1px solid #dfe8f1;
    background: rgba(255,255,255,.98);
    box-shadow: 0 14px 30px rgba(19,50,87,.1);
  }

  .nav.open a { padding: 9px 0; }
}