html {
    height: 100%;
}

body {
    height: 100%;
    background: linear-gradient(0deg, #eee, #fff 80%) no-repeat;
    overflow: hidden;
}

.centered-box {
    margin: 150px auto 0 auto;
    max-width: 420px;
}

.centered-box form .btn {
    cursor: pointer;
}

@media (max-width: 800px) {
    .centered-box {
        margin-top: 30px;
    }
}