Demo tạo button animation với HTML & CSS Live code

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Toidicode.com - Create button animation</title>
    <style>
        body {
            padding: 0;
            margin: 0;
            background-color: #787878;
        }

a {
            position: absolute;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
            background-color: #000000;
            padding: 20px 40px;
            text-decoration: none;
            color: white;
            text-transform: uppercase;
            box-shadow: 0 1px 3px .4px #000000;
            transition: all 0.3s;

}

a:hover {
            box-shadow: 0 1px 7px .4px #000000;
            color: red;
        }

/*TOP*/
        a span:nth-child(1) {
            content: '';
            position: absolute;
            width: 100%;
            height: 3px;
            background: red linear-gradient(to right, black, red);
            top: 0;
            right: 0;
            animation: animationleft 2s linear 0.3s infinite;
        }

/*Right*/
        a span:nth-child(2) {
            content: '';
            position: absolute;
            width: 3px;
            height: 100%;
            background: red linear-gradient(to bottom, black, red);
            top: 0;
            right: 0;
            animation: animationdown 2s linear 0.3s infinite;
        }

/*Bottom*/
        a span:nth-child(3) {
            content: '';
            position: absolute;
            width: 100%;
            height: 3px;
            background: red linear-gradient(to left, black, red);
            bottom: 0;
            right: 0;
            animation: animationright 2s linear 0.3s infinite;
        }

/*Left*/
        a span:nth-child(4) {
            content: '';
            position: absolute;
            width: 3px;
            height: 100%;
            background: red linear-gradient(to top, black, red);
            top: 0;
            left: 0;
            animation: animationtop 2s linear 0.3s infinite;
        }

@keyframes animationdown {
            from {
                transform: translateY(-100%);
            }
            to {
                transform: translateY(100%);
            }
        }

@keyframes animationtop {
            from {
                transform: translateY(100%);
            }
            to {
                transform: translateY(-100%);
            }
        }

@keyframes animationleft {
            from {
                transform: translateX(-100%);
            }
            to {
                transform: translateX(100%);
            }
        }

@keyframes animationright {
            from {
                transform: translateX(100%);
            }
            to {
                transform: translateX(-100%);
            }
        }
    </style>
</head>
<body>
<a href="#">
    <span></span>
    <span></span>
    <span></span>
    <span></span>
    Button
</a>
</body>
</html>