adaptive menu

menu.php

<div class="menu">
  <div class="menu__icon">
        <span></span>
        <span></span>
        <span></span>
        <span></span>
  </div>
    <div class="menu__links">
        <a class="menu__links-item" href="/">Item 1</a>
        <a class="menu__links-item" href="/">Item 2</a>
    </div>
</div>





.menu {
    text-align: right;
}

.menu__links-item {
    display: inline-block;
    color: #333333;
    font-family: Arial;
    font-size: 14px;
    line-height: 30px;
    padding: 0 10px;
    text-transform: uppercase;
    text-decoration: none;
}

.menu__links-item:hover {
    text-decoration: underline;
}

.menu__icon {
    display: none;
    width: 45px;
    height: 35px;
    position: relative;
    cursor: pointer;
}

.menu__icon span {
    display: block;
    position: absolute;
    height: 9px;
    width: 100%;
    background: #333333;
    border-radius: 9px;
    opacity: 1;
    left: 0;
    transform: rotate(0deg);
    transition: .25s ease-in-out;
}

.menu__icon span:nth-child(1) {
    top: 0px;
}

.menu__icon span:nth-child(2), .menu__icon span:nth-child(3) {
    top: 13px;
}

.menu__icon span:nth-child(4) {
    top: 26px;
}

@media screen and (max-width: 999px) {
  .menu__icon{
    display: inline-block;
  }
  
  .menu__links {
    position: fixed;
    display: block;
    top: 0;
    right: 0;
    left: 0;
    margin-top: 52px;
    background-color: rgba(0, 0, 0, 0.8);
    z-index: 1000;
    overflow: auto;
  }
  
  .menu__links-item {
    display: block;
    padding: 10px 0;
    text-align: center;
    color: #ffffff;
  }
}

.menu.menu_state_open .menu__icon span:nth-child(1) {
    top: 18px;
    width: 0%;
    left: 50%;
}

.menu.menu_state_open .menu__icon span:nth-child(2) {
    transform: rotate(45deg);
}

.menu.menu_state_open .menu__icon span:nth-child(3) {
    transform: rotate(-45deg);
}

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

.menu.menu_state_open .menu__links {
    display: block;  
}





(function($){
  $(function() {
    $('.menu__icon').on('click', function() {
      $(this).closest('.menu').toggleClass('menu_state_open');
    });
  });
})(jQuery);