.nav-group {
  position: relative;
  flex: 0 0 auto;
}

.topbar nav .nav-group > button {
  width: 100%;
}

.nav-group > button small {
  margin-left: 3px;
  transition: transform .18s ease;
}

.nav-group.open > button small {
  display: inline-block;
  transform: rotate(180deg);
}

.nav-submenu {
  display: none;
  position: absolute;
  top: calc(100% + 10px);
  left: 0;
  min-width: 205px;
  padding: 8px;
  background: #171717;
  border: 1px solid #ffffff1f;
  border-bottom: 4px solid var(--red);
  border-radius: 0 0 12px 12px;
  box-shadow: 0 14px 28px #0005;
}

.nav-group.open .nav-submenu {
  display: grid;
  gap: 4px;
}

.topbar nav .nav-submenu button {
  width: 100%;
  text-align: left;
  padding: 11px 13px;
}

@media (max-width: 900px) {
  .nav-group {
    position: static;
  }

  .topbar nav .nav-group {
    display: grid;
  }

  .nav-submenu {
    position: static;
    min-width: 0;
    margin-top: 4px;
    border: 0;
    border-left: 3px solid var(--red);
    border-radius: 0;
    box-shadow: none;
    background: #0f0f0f;
  }
}