html {
    background-image: url(../pastevent/imgs/bg_pc.jpg);
    background-repeat: no-repeat;
    background-size: cover;
    background-attachment: fixed;
    background-position: center;
}
body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    margin: 0;
}
main {
    background-color: unset;
    padding-top: 30px;
    flex: 1;
}
footer {
    width: 100%;
    text-align: center;
}
.copyright {
    padding: 0 0 30px;
}
main img {
    display: block;
}
.title {
    width: 300px;
    max-width: 65%;
    margin: auto;
}
#pastlist img {
    margin: 80px auto;
    width: 500px;
    max-width: 80%;
}

@media (max-width: 768px) {
    html {
        background-image: url(../pastevent/imgs/bg_sp.jpg);
    }
    #pastlist img{
        margin: 60px auto;
    }
}