body {
    width: fit-content;
    font-family:
        "Cambria Math",
        "Latin Modern Math",
        "STIX Two Math",
        "SimSun", "宋体",
        "Times New Roman", Times, serif;
    font-size: 1.8vw;
}

.返回 {
    position: fixed;
    margin: 10vh auto auto 2vw;
}

.主框 {
    width: fit-content;
    margin: 10vh auto auto 10vw;
}

.主框 p {
    width: fit-content;
    margin: 0 auto 4vh 0;
    white-space: nowrap;
}