<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="style.css">
    <title>Document</title>
</head>
<body>
    <a href="#">
        <span></span>
        <span id="1"></span>
        <span></span>
        <span id="2"></span>
        Button
    </a>
</body>
</html>

body{
    margin:;
    padding:;
    background:#2f3640;
}
a{
    position: absolute;
    top:50%;
    left:50%;
    transform: translate(-50%,-50%);
    color:#1670f0;
    font-size:60px;
    letter-spacing: 2px;
    text-transform: uppercase;
    text-decoration: none;
    box-shadow: 0 40px 100px rgba(0, 0, 0, .5);
    padding:30px;
    overflow: hidden;
}
a::before{
    content: "";
    position: absolute;
    top:2px;
    left:2px;
    bottom:2px;
    width:50%;
    background:rgba(255, 255, 255, .05)
}
a span:nth-child(1){
    position: absolute;
    top:;
    left:;
    width:100%;
    height:4px;
    background:linear-gradient(to right,#2f3640,#1779ff);
    animation: animate1 1s linear infinite;
}
@keyframes animate1{
    0%{
        transform: translateX(-100%);
    }
    100%{
        transform: translateX(100%);
    }
}
a span:nth-child(2){
    position: absolute;
    top:;
    right:;
    width:4px;
    height:100%;
    background:linear-gradient(to bottom,#2f3640,#1779ff);
    animation: animate2 1s linear infinite;
    animation-delay: 0.5s;
}
@keyframes animate2{
    0%{
        transform: translateY(-100%);
    }
    100%{
        transform: translateY(100%);
    }
}
a span:nth-child(3){
    position: absolute;
    bottom:;
    right:;
    width:100%;
    height:4px;
    background:linear-gradient(to left,#2f3640,#1779ff);
    animation: animate3 1s linear infinite;
}
@keyframes animate3{
    0%{
        transform: translateX(100%);
    }
    100%{
        transform: translateX(-100%);
    }
}

a span:nth-child(4){
    position: absolute;
    bottom:;
    left:;
    width:4px;
    height:100%;
    background:linear-gradient(to top,#2f3640,#1779ff);
    animation: animate4 1s linear infinite;
    animation-delay: 0.5s;
}
@keyframes animate4{
    0%{
        transform: translateY(100%);
    }
    100%{
        transform: translateY(-100%);
    }
}

        var one = document.getElementById("1");
        var two = document.getElementById("2");
        one.style.visibility = "hidden";
        two.style.visibility = "hidden";
        window.setTimeout(function(){
            one.style.visibility = "visible";
        two.style.visibility = "visible";
        },500)