html {
  min-height:100%;
  display:flex;
}
body {
    /*...*/
    /*background-image: url(../images/background-root.jpg);*/
    
}
.open button.menu_btn span:nth-child(1){
	display: none !important;}
.open button.menu_btn span:nth-child(2){
	/*-webkit-transform: translateY(0px)!important;
	-moz-transform: translateY(0px)!important;
	transform: translateY(0px)!important;*/
	-ms-transform: rotate(45deg)!important; /* IE 9 */
    -webkit-transform: rotate(45deg)!important; /* Safari */
    transform: rotate(45deg)!important;
	}
.open button.menu_btn span:nth-child(3){
	/*-webkit-transform: translateY(0px)!important;
	-moz-transform: translateY(0px)!important;
	transform: translateY(0px)!important;*/
	-ms-transform: rotate(135deg)!important; /* IE 9 */
    -webkit-transform: rotate(135deg)!important; /* Safari */
    transform: rotate(135deg)!important;
	}