/**** submenu columns ****/
ul.menu li.submenu-columns ul.children,
ul.menu li.submenu-columns ul.children > li {
  display: -webkit-box  !important;
  display: -webkit-flex !important;
  display: -ms-flexbox  !important;
  display: flex         !important;
}
ul.menu li.submenu-columns ul.children {
  flex-wrap: wrap;
  overflow: hidden !important; /* don't let the width increase after the menu is expanded */
}
ul.menu li.submenu-columns ul.children > li {
  flex-direction: column;
}
ul.menu li.submenu-columns ul.children > li > a {
  flex: 1;
  width: 100%;
}


/**** do not allow the drop-down menu to go beyond the right edge of the main column
!!!!! the drop-down menu becomes permanently visible !!!!!
ul.menu {
  position: relative;
}
ul.menu li.control-right-edge {
  position: static;
}
ul.menu li.control-right-edge ul.children {
  left: auto;
  right: 0;
}
****/