Button Sliding Effect

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Css3 Button Hover Effect with Before Element</title>
    <style>
        body {
            background-color: #383838;
        }
        a.btn {
            display: inline-block;
            padding: 8px 30px;
            text-decoration: none;
            border: #fff solid 3px;
            color: #fff;
            border-radius: 20px;
            font-size: 18px;
            position: relative;
            overflow: hidden;
            transition: 0.35s all ease-in-out;
        }

        a.btn:hover {
            border-color: #ff6600;
        }

        a.btn::before {
            position: absolute;
            content: '';
            width: 100%;
            height: 100%;
            left: -100%;
            top: 0;
            background-color: #ff6600;
            z-index: -1;
            transition: 0.35s all ease-in-out;
        }

        a.btn:hover::before {
            left: 0;
        }

        a.btn.rightBtn::before {
            left: auto;
            right: -100%;
        }

        a.btn.rightBtn:hover::before {
            right: 0;
        }
    </style>
</head>
<body>
    <a href="" class="btn">Button</a>
    <a href="" class="btn rightBtn">Button</a>
</body>
</html>