.top_logo {
  width: 6rem;
}
@media (min-width: 768px) {
  .top_logo {
    width: 10rem;
  }
}
.top_nav {
  height: 4rem;
  border-bottom: 1px solid #ddd;
}
@media (min-width: 768px) {
  .top_nav {
    height: 6.5rem;
  }
}