/*you can use the :checked or the :focus property on the icon you want the user to click and than change the display of the menu from none to whatver you want*/
#yourmenu{
  /*style*/
  display: none;
}
#yourbutton{
  /*style*/
}
#yourbutton:checked > yourmenu{
  display: block;/*whathever value you want*/
}
/*sorry for the shitty english, hope to help someone with this concept*/