.menu {
  cursor: pointer;
  height: 24px;
  list-style: none;
  margin: 0;
  padding: 0;
  width: 30px;
  position: relative;
  -webkit-transform: rotate(0deg);
     -moz-transform: rotate(0deg);
       -o-transform: rotate(0deg);
          transform: rotate(0deg);
  -webkit-transition: .3s ease-in-out;
     -moz-transition: .3s ease-in-out;
       -o-transition: .3s ease-in-out;
          transition: .3s ease-in-out;
}

.menu li {
  background-color: white;
  border-radius: 4px;
  display: block;
  height: 2px;
  left: 0;
  margin: 0;
  opacity: 1;
  padding: 0;
  position: absolute;
  width: 100%;
  -webkit-transform: rotate(0deg);
     -moz-transform: rotate(0deg);
       -o-transform: rotate(0deg);
          transform: rotate(0deg);
  -webkit-transition: .15s ease-in-out;
     -moz-transition: .15s ease-in-out;
       -o-transition: .15s ease-in-out;
          transition: .15s ease-in-out;
} 

.menu li:nth-child(1) {
  top: 0;
  -webkit-transform-origin: left center;
     -moz-transform-origin: left center;
       -o-transform-origin: left center;
          transform-origin: left center;
}

.menu li:nth-child(2) {
  top: 9px;
  -webkit-transform-origin: left center;
     -moz-transform-origin: left center;
       -o-transform-origin: left center;
          transform-origin: left center;
}

.menu li:nth-child(3) {
  top: 18px;
  -webkit-transform-origin: left center;
     -moz-transform-origin: left center;
       -o-transform-origin: left center;
          transform-origin: left center;
}

.menu.open li:nth-child(1) {
  left: 4px;
  top: -1px;
  -webkit-transform: rotate(45deg);
     -moz-transform: rotate(45deg);
       -o-transform: rotate(45deg);
          transform: rotate(45deg);
}

.menu.open li:nth-child(2) {
  opacity: 0;
  width: 0;
}

.menu.open li:nth-child(3) {
  left: 4px;
  top: 20px;
  -webkit-transform: rotate(-45deg);
     -moz-transform: rotate(-45deg);
       -o-transform: rotate(-45deg);
          transform: rotate(-45deg);
}