/* root categories, first level category links */
.horizontal-menu-item--levelTop {
  font-size: 16px;
}

/* subcategories, second level category links */
.horizontal-menu-item--levelChild {
  font-size: 14px;
}

/* 3rd, 4th, etc level category links */
.horizontal-menu-item--levelChild .horizontal-menu-item--levelChild {
  font-size: 13px;
}