@media (max-width: 850px) {
  .nav-wrap { position: relative; }
  nav.is-open {
    display: flex;
    position: absolute;
    top: 70px;
    right: 0;
    left: 0;
    flex-direction: column;
    gap: 18px;
    padding: 20px;
    background: var(--paper);
    border-bottom: 1px solid var(--line);
  }
}