html,
body {
    height: 100%;
}

body {
    display: flex;
    align-items: center;
    padding-top: 40px;
    padding-bottom: 40px;
    background-color: #f5f5f5;
}

.auth-box {
    width: 100%;
    max-width: 600px;
    padding: 15px;
    margin: auto;
}

.custom-btn {
    padding: 10px 30px;
}