#menu {
    padding-top: 1rem;
    background-color: #fafafa;
    width: 16em;
    position: fixed;
    top: 4em;
    left: 0;
    z-index: 1;
    bottom: 0; /* 或 height: 100vh; */
    right: 0;
    overflow: auto;
}


@media (max-width: 736px) {
    .menu-mobile {
        background: #fff;
        width: 16em;
        box-shadow: 0 0 5px rgba(0, 0, 0, 0.1);
        transition: .1s ease left;
    }
    .menu-mobile-hidden {
        display: none;
    }
}

#menu a {
    color: inherit;
    /*text-decoration: none;*/
}

/*折叠*/
#menu ul {
    list-style: none;
    padding-left: 1em;
}

#menu li {
    cursor: pointer;
    position: relative;
    padding-left: .8em;
    margin-bottom: 0.3em;
    user-select: none;
}

#menu li > p{
    margin: 0;
}

#menu li.collapsible::before {
    content: '>';
    position: absolute;
    left: 0;
    font-size: 0.8em;
    font-weight: bold;
    transition: transform 0.2s;
    color: #d29922;
}

#menu li.expanded::before {
    transform: rotate(90deg);
}