.menu{
  overflow: hidden;
  height: 0;
  width: 100%;
  position: fixed;
  top: 0;
  left: 0;
  z-index: 100;
  transition: height 0.3s ease-in;
}

#toggle-menu-btn{
  position: fixed;
  right: 16px;
  top: 16px;
  z-index: 100;
}