article-catalog {
    --top-margin: calc(4.5rem + 12px);
    --item-margin-step: .875rem;

    color: var(--default-tx-color);
    background-color: var(--default-bg-color);
    overflow: auto;
    box-sizing: border-box;
    z-index: 100;
    transition: background .6s,
                border-radius .3s .15s,
                transform .45s;
}

@media print {
    article-catalog {
        display: none;
    }
}
@media screen and (min-width: 768px) {
    /* desktop styles */
    article-catalog {
        position: sticky;
        top: 0;
        height: calc(100vh - var(--top-margin));
        border-top-right-radius: 1rem;
        border-bottom-right-radius: 1rem;
        box-shadow: var(--shadow-lg);
    }
    article-catalog.top-stuck {
        border-top-right-radius: 0;
    }
    article-catalog.bottom-stuck {
        border-bottom-right-radius: 0;
    }
}
@media screen and (max-width: 767px) {
    /* mobile styles */
    article-catalog {
        position: fixed;
        top: calc(var(--top-margin) + 4rem) !important;
        left: var(--page-horizonal-padding);
        right: var(--page-horizonal-padding);
        bottom: 0;
        height: auto;
        border-top-left-radius: .75rem;
        border-top-right-radius: .75rem;
        box-shadow: var(--shadow-md-2);
    }
    #article-container:not(.with-catalog) article-catalog {
        transform: translateY(calc(100% + 16px));
    }
}

article-catalog ol li {
    border-top-right-radius: 0;
    border-bottom-right-radius: 0;
    user-select: none;
    cursor: pointer;
}

article-catalog li * {
    /* prevent to trigger events */
    pointer-events: none;
}

article-catalog .level-h1 {
    font-weight: bold;
}
article-catalog .level-h2 {
    /* ignored */
}
article-catalog .level-h3 {
    margin-left: calc(var(--item-margin-step) * 1);
}
article-catalog .level-h4 {
    margin-left: calc(var(--item-margin-step) * 2);
}
article-catalog .level-h5 {
    margin-left: calc(var(--item-margin-step) * 3);
}
article-catalog .level-h6 {
    margin-left: calc(var(--item-margin-step) * 4);
}