#main-menu.is-open { display: block;
}

@-webkit-keyframes mmfadeIn {
  from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes mmfadeIn {
  from { opacity: 0; }
    to { opacity: 1; }
}

@-webkit-keyframes mmfadeOut {
  from { opacity: 1; }
    to { opacity: 0; }
}

@keyframes mmfadeOut {
  from { opacity: 1; }
    to { opacity: 0; }
}

#main-menu[aria-hidden="true"] {
  -webkit-animation: mmfadeOut .75s;
          animation: mmfadeOut .75s;
}

#main-menu[aria-hidden="false"] {
  -webkit-animation: mmfadeIn .75s;
          animation: mmfadeIn .75s;
}