Edit in JSFiddle

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    <link rel='stylesheet prefetch' href='https://fonts.googleapis.com/icon?family=Material+Icons'>
    <style class="cp-pen-styles">#navigation-bar{
      position:relative;
      height:25px;
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      #search{
        position:absolute;
        top:0;
        right:0;
        width:25px;
        height:25px;
      }
      #label{
        width:25px;
        height:25px;
        position:relative;
        z-index:20;
      }
      #label label{
        display:block;
        height:25px;
        width:25px;
        color:#ccc;
        cursor:pointer;
      }
      #label label:hover{
        color:#898989;
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      #input{
        position:absolute;
        top:0;
        right:25px;
        width:150px;
        height:25px;
        z-index:5;
        overflow:hidden;
      }
      #input input{
        display:block;
        position:absolute;
        top:0;
        right:-150px;
        width:150px;
        height:100%;
        margin-left:10px;
        margin-right:-60px;
        padding-left:0px;
        border:none;
        background-color:#fff;
        font-size:12px;
        backface-visibility:none;
        border-radius:0;
        transition:right 0;
      }
      #input input:focus{
        outline:none;
      }
      #input.focus{
        z-index:20;
      }
      #input.focus input{
        right:0;
        transition:right 0.5s;
      }
    </style>
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  <body>
    <div id="navigation-bar" class="clearfix">  
      <form id="search" action="/search" method="GET" target="_top">    
        <div id="label">
          <label for="search-terms" id="search-label" class="material-icons">&#xE8B6;
          </label>
        </div>    
        <div id="input">
          <input type="text" name="q" id="search-terms" placeholder=" Search...">
        </div>  
      </form>
    </div>
    <script src='//production-assets.codepen.io/assets/common/stopExecutionOnTimeout-b2a7b3fe212eaa732349046d8416e00a9dec26eb7fd347590fbced3ab38af52e.js'>
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    <script src='https://cdnjs.cloudflare.com/ajax/libs/classie/1.0.1/classie.min.js'>
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    <script>(function(window){
        // get vars    var searchEl = document.querySelector("#input");    var labelEl = document.querySelector("#label");    // register clicks and toggle classes    labelEl.addEventListener("click",function(){        if (classie.has(searchEl,"focus")) {            classie.remove(searchEl,"focus");            classie.remove(labelEl,"active");        } else {            classie.add(searchEl,"focus");            classie.add(labelEl,"active");        }    });    // register clicks outisde search box, and toggle correct classes    document.addEventListener("click",function(e){        var clickedID = e.target.id;        if (clickedID != "search-terms" && clickedID != "search-label") {            if (classie.has(searchEl,"focus")) {                classie.remove(searchEl,"focus");                classie.remove(labelEl,"active");            }        }    });}(window));//# sourceURL=pen.js</script>
  </body>
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