@media screen and (max-width: 480px) {
    div[epub|type="chapter"] {
        background-position: top center, bottom center;
        background-size: 30% auto, 50% auto;

        margin: auto;
        padding: 1em;
        text-align: center;
    }

    h1 {
        font-size: 1em;
        margin: 50% auto 0 0;
        text-align: center;
    }

    p { margin-left: 25%; }
}