@media only screen and (max-width: 1200px) {
    header {
        width: 70%;
    }

    main {
        width: 70%;
    }

    iframe {
        height: 300px;
    }

    .personagens ul,
    .livros ul {
        flex-direction: column;
        margin: auto;
    }

    .personagens ul li,
    .livros ul li {
        display: block;
        width: 95%;
        margin: 0 auto;
        margin-bottom: 10px;
    }

    .personagens ul li img,
    .livros ul li img {
        width: 40%;
        float: left;
        margin: 1em 1em;
    }

    .livros ul li img {
        height: 290px;
    }
}

@media only screen and (max-width: 450px) {

    header {
        width: 70%;
    }

    main {
        width: 70%;
    }

    nav ul {
        display: flex;
        flex-direction: column;
    }

    iframe {
        height: 200px;
    }

    .personagens ul,
    .livros ul {
        display: flex;
        flex-direction: column;
        justify-content: space-around;
        margin: 0 5px;
    }

    .personagens ul li,
    .livros ul li {
        display: flex;
        flex-direction: column;
        justify-content: space-between;
        align-items: baseline;
        width: 100%;
        margin: 5px 0;
    }

    .personagens ul li img,
    .livros ul li img {
        width: 90%;
        margin: auto;
        margin-top: 1em;
    }
}