幽灵按钮

<style>
    *{margin: 0; padding:0;}
    .btn{
        position: relative;
        display: inline-block;
        padding: 0 40px 0 15px;
        border: 2px solid rgba(255, 255, 255, 0.4);
        color: #fff;
        font-size: 14px;
        text-decoration: none;
        line-height: 30px;
        -webkit-transition: 0.2s ease;
        -moz-transition: 0.2s ease;
        -ms-transition: 0.2s ease;
        -o-transition: 0.2s ease;
        transition: 0.2s ease;
    }
    .btn i{
        position: absolute;
        top: 0;
        right: 20px;
        color: #fff;
        font-size: 12px;
        -webkit-transition: 0.2s ease;
        -moz-transition: 0.2s ease;
        -ms-transition: 0.2s ease;
        -o-transition: 0.2s ease;
        transition: 0.2s ease;
    }

    .line{position: absolute;
        opacity: 0;
        background: #fff;
        -webkit-transition: 0.2s ease;
        -moz-transition: 0.2s ease;
        -ms-transition: 0.2s ease;
        -o-transition: 0.2s ease;
        transition: 0.2s ease;
    }
    .line-top{
        width:0;
        height: 2px;
        left: -110%;
        top: -2px;
    }
    .line-right{
        right: -2px;
        top: -110%;
        width:2px;
        height: 0;
    }
    .line-bottom{
        width:0;
        height: 2px;
        right: -110%;
        bottom: -2px;
    }
    .line-left{
        left: -2px;
        bottom: -110%;
        width:2px;
        height: 0;
    }
    .btn:hover .line{
        opacity: 1;;
    }
    .btn:hover .line-top{
        left: 0;
        width: 100%;
    }
    .btn:hover .line-right{
        top: 0;
        height: 100%;
    }
    .btn:hover .line-bottom{
        right: 2px;
        width: 100%;
    }
    .btn:hover .line-left{
        bottom: 0;
        height: 100%;
    }
    .btn:hover{
        border: 2px solid #fff;
    }
    .btn:hover i{
        right: 10px;
    }
</style>
<div style="width:400px; padding:100px; margin: 0 auto; background: #444444;">
    <a href="#" class="btn">
        Buttons
        <span class="line line-top"></span>
        <span class="line line-right"></span>
        <span class="line line-bottom"></span>
        <span class="line line-left"></span>
        <i>→</i>
    </a>
</div>