button hamburger

index.html

<div class="btn-menu-sp">
  <span></span>
  <span></span>
  <span></span>
  <span></span>
</div>

script.js

$(this).toggleClass('open');

style.css

    /*
    hamburger menu
    */
    .btn-menu-sp {
        width: 30px;
        height: 23px;
        position: relative;
        -webkit-transform: rotate(0deg);
        -moz-transform: rotate(0deg);
        -o-transform: rotate(0deg);
        transform: rotate(0deg);
        -webkit-transition: .5s ease-in-out;
        -moz-transition: .5s ease-in-out;
        -o-transition: .5s ease-in-out;
        transition: .5s ease-in-out;
        cursor: pointer;
    }

    .btn-menu-sp span {
        display: block;
        position: absolute;
        height: 1px;
        width: 100%;
        background: #707070;
        opacity: 1;
        left: 0;
        -webkit-transform: rotate(0deg);
        -moz-transform: rotate(0deg);
        -o-transform: rotate(0deg);
        transform: rotate(0deg);
        -webkit-transition: .25s ease-in-out;
        -moz-transition: .25s ease-in-out;
        -o-transition: .25s ease-in-out;
        transition: .25s ease-in-out;
    }

    .btn-menu-sp span:nth-child(1) {
        top: 0px;
    }

    .btn-menu-sp span:nth-child(2), .btn-menu-sp span:nth-child(3) {
        top: 12px;
    }

    .btn-menu-sp span:nth-child(4) {
        top: 23px;
    }

    .btn-menu-sp.open span:nth-child(1) {
        top: 12px;
        width: 0%;
        left: 50%;
    }

    .btn-menu-sp.open span:nth-child(2) {
        -webkit-transform: rotate(45deg);
        -moz-transform: rotate(45deg);
        -o-transform: rotate(45deg);
        transform: rotate(45deg);
    }

    .btn-menu-sp.open span:nth-child(3) {
        -webkit-transform: rotate(-45deg);
        -moz-transform: rotate(-45deg);
        -o-transform: rotate(-45deg);
        transform: rotate(-45deg);
    }

    .btn-menu-sp.open span:nth-child(4) {
        top: 18px;
        width: 0%;
        left: 50%;
    }